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Aerospace Engineering - Science topic

Space Systems, Aerospace Sciences and Engineering. Dynamical Systems and Robotics.
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What is the mechanism of fuel and oxidizer mixing used in ISRO's designed VIKASH Rocket engine?
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This is not my area, but this could be relevant?;
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Hi. I'm going to optimize the layout design of the satellite with Abaqus and Isight. I designed and analyzed the Abaqus model, which is pinned below. Now I want to enter my model to Isight to optimize satellite, but I face a big obstacle. The Abaqus should enter the reference points and constraints points in Isight to optimize the parts' location, but there is nothing like RF points or constraints points. I couldn't find a way to solve this problem. May someone helps me to figure it out?
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Thank you for sharing the finite element model. Do you consider additional constraints such as natural frequencies, moments of inertia, center of gravity?
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Hello Professors and researchers,
I am a new faculty member who has joined at Department of Aerospace Engineering, VIT Bhopal. The university is renowned for teaching in the country. As a person who has gained international experience in a german laboratory working as a scientist, and also a PhD from QS ranking institute, I now look forward to setup own laboratory dealing with research on Aerodynamics, fluid mechanics and CFD. I have published several papers in journals and conferences. I would like to know how one could setup own lab without much expenditure on facilities and R&D funding but has adequate access to student interaction (manpower only) free of cost. How can I start?
Please provide your suggestions. If you are willing to collaborator as well, a warm welcome.
--
Dr. Aravind Seeni
Assistant Professor
VIT Bhopal
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Dear Aravind,
You are welcome.
Regards
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Q. : Students asked me that "we only study about different forms of energy, one form of energy getting converted to another forms of energy. But no one knows what is energy."
Ans: No answer
Q. Sir Why do we have to call something by the name that a scientists used long back, can't we change it.
Ans: Science or engineering is field of perspective, how one looks at something matters. But everything that you read in a book can be changed. If you wish you can express it in a different manner.
It is the terminology, that we learn, in which people who observed certain phenomenon used to explain a particular concept we follow. Learn. To make world understand what you have to say you have to first make them ready to understand. Otherwise no one would know.
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Aditya Kumar Mishra Scientific answers are already cited by many experts aI can say depending upon the simplest form is that Energy is nothing but ability to do the work......
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In comparison with a flat plate solar air collector and solar air collector with 10-meter tube. Which one should be taken for air velocity measurement? Inlet air velocity, outlet air velocity, average, Ashrea standard or ....
Pressure loss is 275 Pa in tube collector.
How can I measure with hotwire? How and where should I put it?
Thanks.
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You could just install an orifice meter at the inlet pipe to the solar air heater to measure the air flow rate
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The force transmitted to a beam part, due to an impact analysis, is shown in attached figure. The figure shows the beam shear force with respect to time due to impact. The maximum beam shear allowable is 1500 lbs, whereas during impact, the beam dynamic peak force reaches more than 2000 lbs (at time 3e-3, 4.5e-3 and 5.5e-3 seconds). Does this beam fail due to the impact loading? For this I was thinking to convert the dynamic force to equivalent static force to compare with the beam allowable (1500 lbs). Would it be possible to find the equivalent static force for this dynamic force shown? Thanks in advance.
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Any explanation for time step size definition for fluent ?
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Time step size is the minimum division of the time on which the maximum iteration you have given is going to perform. If you have to run a simulation for 200 seconds then you have to take the number of time steps 2000 for 0.1sec time step size or number of time steps20000 for 0.01sec time step size. Whereas the maximum iteration/time step should be taken as 10-20, wherever the values of residuals are converging.
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Hello everyone,
I am an Aerospace Engineering student and I would like to work on a numerical simulation. As I wrote in the title, I would like to study the effects of wind on an industrial chimney. In particular, I already know how to model the vortex shedding problem in Ansys-Fluent. I would therefore like to know how to study the effect of these periodic forces on a chimney. Which program should I use? Which code should I use?
Thanks to those who will help me
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As you mention... know how to model the vortex shedding problem in Ansys-Fluent. For a study of vortex shedding the important requirement is the frequency and the proportionality factor for vortex shedding is named Strouhal number.
I think setup a few points in the wake region for u-components and that should fluctuate with a certain frequency, Try to use FFT and mark your needed frequency from that.
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I studied journals on SLM (Selective Laser Melting) produced Al12Si components
In that many authors used Solution heat treatment/ annealing.
but for AlSi10Mg they used T6 heat treatment
why can't we use the same T6 for Al12Si?
Your answers help me a lot
Thanks in Advance
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Thank you for answering
What I understand from the above two answers is
by looking phase diagram, at AA temperature (150-1800 C), the solubility of Si in Aluminum gets zero but in Al10SiMg because of Mg content Si is not precipitated and forms Mg2Si
Correct me if I am wrong
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As I know, the ordinary differential equation (ODE), xdot= -x^3+u, where x is the state variable, and u the control variable, is the control system associated to a falling object in atmosphere with viscous drag. I am not sure to be correct on that! Please comment on that!.
Update 1: xdot= -x^3+u, is called the hyper-sensitive system.
c.f.: A Collection of Optimal Control Test Problems: John T Betts.
Another example is velocity control for aircrafts in horizontal flight, which has an ODE evolution:
xdot=-x^2+u. Notice the attachment picked from:
Optimal Control with Engineering Applications; By: Hans Peter Geering.
I want to also know the real model associated to the control system described by the ODE: xdot= x^3+u. I guess more probably, this is associated to electrical systems.
Update 2: My own intuition says, positively damped systems as:
x_dot+x^3=u
are mechanical. Meanwhile, negatively damped systems as:
x_dot-x^3=u
are electrical.
You can yourself find some other examples in this regard.
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Thanks for showing the disturbance suppression capability of your proposed controller. However, I'm unsure what you meant by "injecting a step-function as a disturbance input". The disturbance is a sinusoidal signal.
I have tuned the PD gains so that you can compare both of them meaningfully. The setpoint or the reference target value for the process variable (x) of the double integrator is 1. The double integrator is also loaded with a sinusoidal disturbance of 0.1*sin(t).
x'' = - Kp*(x - 1) - Kd*x' + 0.1*sin(t); x(0) = 0; x'(0) = 0
where Kp = 0.002304, and Kd = 0.096.
The final value of the process variable (x) oscillates within the magnitudes of 1 ± 0.1.
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I make a simulink file to link the FlightGear with MATLAB, i use Function Block Parameters, Sink Block Parameters and Generate Run Scrip. When i run simulink file i see this error:"The Mux blocks used to create bus signals diagnostic must be set to 'Error' to prevent modeling errors (see the Mux block documentation for more information). Open the Upgrade Advisor to identify and fix upgrade problems". So I want to know how can i solve this problem to run both MATLAB and FlightGear?
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I implemented the simulink - flightgear interface from scratch, and without relying on the dedicated toolbox provided by Mathworks.
Please feel free to check it out here.
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Assuming two-dimensional flow, I'm trying to implement a code for a quasi DNS problem. There is no doubt that i should replace the velocities in Navier-Stokes equation (NSE) with its equivalent velocities in the form of u=u_base + uf, where u_base is the steady state solution for NSE for the channel flow and uf is the perturbed velocity which varies with time. By the new definition of the velocities, one can get new extra terms in NSE, as a function of u_base and uf. My point is to find the fluctuation behavior with time so that i can calculate the growth rate and start an instability study for the flow field.
There are two forms of the new NSE, maybe more but at least these two were the common equations which i found in most of the researches which i read. The first one is in the form of du/dt + div(uu) = - dp/dx+ iv(grad(u))/Re where u was defined earlier. The second form is: du/dt + div(uu) = - dp/dx+ div(grad(u))/Re - omega x u.
Which one should i use for the purpose of instability studies?
Note: You can check the attached files for the non-conservative form of the two previous models.
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Thank you for your answer dear
Ijaz Durrani
I really appreciate your suggestion. Unfortunately, the authors were using an averaged model, which is not the case i'm looking for.
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Hello everyone,
I want to learn performing Structural Analysis for rotorcrafts and looking for some instructions on how to plot V-n Diagram and perform Loading Analysis, Stress Analysis, Damage Analysis, Fatigue etc..
Some references like AMCP 706-202 helped me out but I'm still looking for some more help.
And how can I get "ADS-29, Structural Design Criteria for Rotary Wing Aircraft"? Will it help?
Best Regard
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I want to know the exact definition of these four tests and I am wondering which of them could work in real time?
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HIL or 'hardware-in-the-loop' testing is by its very nature a resource-hungry solution to testing, requiring multi-skilled teams able to set up and configure both the execution platform and the I/Os as well as the modelling environment.
Once your model is verified (i.e., MIL in the previous step is successful), the next stage is Software-in-Loop(SIL), where you generate code only from the Controller model and replace the Controller block with this code.
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I want to model lazy eight maneuver by matlab simulink or AI.
what shall I do???
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I am trying to simulate the impact of a 9mm bullet into a composite metal foam (steel) panel.
I might ask more questions in the near future so if anyone with knowledge about the topic and free time wants to help me, feel free to contact :D
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Okey the inertia is assigned if you define the bullet or impact object as discrete rigid. Because Abaqus wont let you assign a material to the object so no density will be given to it.
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Hi,
Previously I worked on combustion engines....
But now due to my new adviser, i want to work on nanotechnology...
I want to work on a subject that relates to both nano and engine ...
Do you have any suggestion?
Regards
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Dear Dr.
Yes, this is a work of modern methods. For delicious reasons, adding nanoparticles has many advantages. It has the ability to improve the performance and emissions in the engine as well as improving the thermal behavior of the engine. Adding nanoparticles to improve Oil by adding these materials to the lubricant oils. There are many advantages.
Best Regards
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NFF (No Fault Found) has the major contribution to reduce the operational availability, resources and increase the cost of Maintenance of any aircraft in aviation. The likely causes are human factors, maintenance training, faults reporting, fault analysis, corrective Maintenance and procedures. However, mitigating these issues are completely a tedious process wherein management skill can't achieve the desired results. So, what are the other parameters/ technical factors that need to be considered?
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Absolutely right sir. @Mr.Russel King.
Thank you.
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I am recently doing some research on the optimization of 3D contoured endwall. And saw some papers related on it. 
But I am wandering which cascade should I choose to do on it, annular or flat?
should I have to choose annular because it is more like the real engine, (but my test rig is imcompressible)
should I have to choose flat cascade because the flow feature is more simplicated?
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You can study end wall profiling in either of the two rigs you suggest. And as you say the annular one looks rather more like an engine. The use of incompressible flow is fine unless the "real" case you are simulating happens to be supersonic where shockwaves will cause steps in pressure that you cannot simulate at low Mach number. The important rule is that the design of your endwalls is carried out at the same Mach number as your experiment.
Back to your question about annular or otherwise. An important feature of annular cascades is that the spinning of the fluid at row exit is associated with a radial pressure gradient (as happens in engine). This pressure gradient transforms the nature of the secondary flow. High loss fluid will migrate radially inwards. This makes the suction side boundary layer and the loss cores fall towards the hub suction side corner. If your design focus is to modify the end walls only then you cannot address these radial flow effects satisfactorily. This means that the proportional reduction of secondary loss is reduced. How ever the general rule is that the stronger the secondary flow in the initial geometry the stronger the potential benefit of endwall optimisation. This suggests that having a cascade of low aspect ratio will make the secondary flow worse, but the improvement better.
Good luck either way
Martin Rose
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Considering the powered descent guidance problem for a spacecraft or launch vehicle - Early publications by Acikmese, et.al. used lossless convexification to solve the landing guidance problem using point mass dynamics.
Literature that dealt with the powered descent guidance problem using 6 DoF dynamics, also by Acikmese, et.al. proposed the use of successive convexification, with the reasons being that lossless convexification could not handle non-convex state and some classes of non-convex control constraints.
I have the following questions with respect to the above
1) Why is it that Lossless convexification cannot handle some classes of non-convex control constraints ? and what are those classes ? (e.g. the glideslope constraint)
2) What is it about lossless convexification that makes it unsuitable to operate on non-convex state constraints ,as opposed to successive convexification ?
2) Are there specific rotational formalisms ,e.g. quaternions, DCMs, Dual quaternions, MRPs, etc. that are inherently convex ? if so, how does one go about showing that they are convex ?
I would be much obliged if someone could answer these questions or atleast provide references that would aid in my understanding of the topic of convexification.
Thank you.
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Dear Adhithya Babu,
A successive convexification algorithm designed to solve non-convex constrained optimal control problems with global convergence and it can handle nonlinear dynamics and non-convex state and control constraints. However lossless convexification cannot handle nonlinear dynamics. For the third question the answer is affirmative.
For more details and information about your questions I suggest you to see links and attached files on topic.
Best regards
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Using LEA-M8T receiver from U-Blox, I parsed navigation data and after computing user position, I found that something is wrong. I think I should verify satellite positions calculated first. How can I perform it? and If the calculation method is false, How can I calculate satellite's position? 4th Runge-Kutta is not enough... (ECEF in Td is differ from ECEF in receiver Time)
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How to set the initial condition in ECEF? Can you elaborate the answer how you varified the satellite positions exactly?
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Hello, I am performing an undergraduate finite element analysis research project, and my current task is to find the shear center for an asymmetric C beam. Out of curiosity, how does one go about doing this? (picture of profile attached, I am also just taking a mechanics of materials course at my university as we speak)
I wish you all a wonderful day
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Corresponding Python script
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If some one want to do off design simulations for variable geometry compressor engine in GasTurb , is it possible to see the performance of the engine at different kind of varying angles. Because as i know , GasTurb considers some default VG factors a, b and c with a=b=1 and c=0.01...The confusion here is , how to encounter different angles for VIGVs and VSVs..if it is possible , then can we get compressor map with designated angles....?
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Dear Muhammad
Besides not being answer to your question, I do not know how to answer. We developed our own computer programs to deal with variable geometry compressors, turbines and propelling nozzles. These components are designed and their performances calculated using our own software. A set of compressor, turbine and propelling nozzles maps are synthesized (one each for different angles and interpolated for angles not covered in the maps). It is not difficult task, but takes time to develop, verify and certify every piece of software.
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We know that mathematicians study different mathematical spaces such as Hilbert space, Banach space, Sobolev space, etc...
but as engineers, is it necessary for us to understand the definition of these spaces?
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Yes, we do have to know about the spaces, at least during our university studies, to enables us to expand our mind into abstact level, that will be very usefull for design activities
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Hi, can anybody please let me know if there any software package for calculating planetary orbital element determination? For instance, if the position of two points (radius), true anomalies of the points, and flight time of a planetary transfer ellipse are given, then, how to calculate the line of apsides using a software? I understand that I can do it manually in the trial-and-error procedure, but I would like to use the software, if any.
Thank you!
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Hello Al, if I understood correctly the problem you described is known as Lambert's Problem. I am not aware of a specific software, but I know of two great solver scripts that can be found on github:
In Python:
In Matlab:
If you look for Lambert's Problem or Lambert solver I'm sure you will find code for other languages as well.
All the best!
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I am looking for material which can replace aluminium in aerospace industry as i want material which will be having high melting point and must be light in weight. As i am looking at this from commercial point of view so if that material is easily available and cheap then it would be better. Especially Aluminium 7075
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I'm a 3rd year BEng Aerospace Engineering student and looking for research ideas on aero-acoustics and aerospace
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dear student kindly ping me at Jvmlal@ymail.com Ahmed Yassir Bouslalah
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Which kind of materials changed history and why?
What is the future of materials?
which kind of them will have a big change in the future?
Do you know a professor or researcher that is working on the top and new research fields? If you know them or yourself is one of them, please introduce their or your new research topics and introduce them or yourself to researchers.
Thank you so much
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Which materials changed the History ? For example, carved stone, bronze and iron changed the History in its own moment, leading to the corresponding Ages of Stone, Bronze and Iron of the Mankind. These Materials allowed the fabrication of better tools that allowed in turn to control the environment (more intensive agriculture, more sofisticated manufactured goods). Cooked clays permitted storage that in turn permitted longer life shelf and water transportation, and the first buildings and writing pieces in Mesopotamia. Paper was another material that changed the History, allowing to keep the written words and then spread the knowledge. Then plastics, that made everything cheap but that become a nightmare latter (thus changing again the History).
Which materials will change the future? Not talking which compounds, but the types of materials we could mention: Bioinspired materials made with the architectures, functionalities and raw sources from biological things and smart materials that will react to the needs of the user or to the changes in the environmental conditions. These materials should come from sustainable sources or have to be so specialized that would allow their use in a profitable scale.
Hope you find these comments useful.
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I need to know about tip deflection ranges for 2 seat airplane specifically
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Dear Eng. Omar
If one imagines the wing as a cantilever beam under distributed vertical lifting force, which should balance the total weight of the airplane during cruising steady flight, the approximate formula for calculating the wing tip deflection may have the form:
Delta(Tip)= F.O.S. * [ W b^3 / 16 EI]
where F.o.s.= Safety factor (1.2 - 1.5) for gusts and dynamic effects
W = Total weight of the airplane
b= semi span = length of the cantilevered wing
EI= equivalent bending stiffness of the wing cross section
(Depends on material of construction and second moment of area)
I wish you the best
Thanks
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I am trying to measure the forces involved in the impact of a spear on a ballistic gel target. I need an inline sensor to measure this (placed in the spear). The products I have found are either load cells of force gauges. What is the difference between the two and would either work for my application?
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Following
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Design and testing of aerodynamics;
Evaluation of heat transfer of secondary air systems.
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I think its good with www.freefullpdf.com
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Thermal analysis is the first step to thermal control subsystem design ?
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I recommend Firoz Ahmad 's answer
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I want to measure the radiative transfer of the killauea volcano Hawaii. I am interested in SO2 gases
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I recommend Frank's answer
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I am running a steady periodic propeller simulation using the MRF approach (60 deg, periodic). I have had good results by setting the blade zone as the rotational one and having the rest as stationary (Traditional setting for MRF as far as I understand) so my question is ... Do you have any experience with these kind of simulations but using all as rotating zones rather than using only one? Do you know if is better in order to see the vorticity behind the blade?
If I use all-rotating approach, part of the geometry has to be a moving wall since that part is not rotating in reality. 
Of course I can try by actually simulating it but it takes time. That is why your  answer might save me some days :)
Thanks in advance!
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I am agreed with Stephan C. Kaiser
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I want to analyze the amount of SO2 emitted from volcanic activity. I will use ASTER TIR because they provide multispectral TIR data.i saw some people talking about streaching. But, I don't know how to do it.
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I am agreed with Dr.Khaled Al-Farhany
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I have been working in cryogenic loop heat pipe that is used for space thermal control, and it works in 35K or 20K and it is mainly experiment observation. Now I want to change my research a little in cryogenic heat and mass transfer, is there some new and fresh research direction for suggestion?
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Hello to research gate community. I'm simulating a solar collector. I want to calculate sun direction vector whereas the sun rays are perpendicular to the collector. But I don't know how I can do it. Would you mind please tell me about it and also about S2S settings (as a radiation model in Ansys Fluent)?
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Hello, Do u know the relationship between the " sun direction vector" in solar load model and " beam direction "in the wall radiation boundary
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As usually the trend is a Courant number (CFL no) can only be used for a Transient( Unsteady) flow condition.
Thank you in Advance.
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The short answer is Fluent uses the CFL number to compute the time step (even for steady flows). A more detailed explanation follows...
The coupled set of governing equations is discretized in time for both steady and unsteady (transient) calculations. In the steady case, it is assumed that time marching proceeds until a steady-state solution is reached. Temporal discretization of the coupled equations is accomplished by either an implicit or an explicit time-marching algorithm. In the Explicit Formulation the time step is computed from the Courant-Friedrichs-Lewy (CFL) condition. The time step is a function of: the cell volume, the cell face area, and the maximum of local eigenvalues.
Here is some additional information straight from the theory guide (Fluent Version 6) in the section: Steady-State Flow Solution Methods.
For steady-state solutions, convergence acceleration of the explicit formulation can be achieved with the use of local time stepping, residual smoothing, and full-approximation storage multigrid.
Local time stepping is a method by which the solution at each control volume is advanced in time with respect to the cell time step, defined by the local stability limit of the time-stepping scheme.
Residual smoothing, on the other hand, increases the bound of stability limits of the time-stepping scheme and hence allows for the use of a larger CFL value to achieve fast convergence.
The convergence rate of the explicit scheme can be accelerated through use of the full-approximation storage (FAS) multigrid method.
By default, FLUENT uses a 3-stage Runge-Kutta scheme for steady-state flows that use the density-based explicit solver.
Hope this helps!
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Dear all,
I need good and up to date resources to find out the applications of nanotechnology at industry.
Thanks
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a lot of the above will depend heavily what industry you look at as there are basically unlimited application examples, and no single source can cover metallurgy, semiconductor industry, building industry, medicine, pharmaceuticals etc.
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Hi
I want to know that what are the applications and study fields of nanotechnology in Fluid Mechanics?
As I read about nanotechnology applications all of them related to Material Engineering or Chemical Engineering....
Thanks,
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Hi following applications can be noted: Electronic device cooling, transformer cooling, silicon mirror cooling, vehicles cooling, controlling fusion, nanocryosurgery, magnetic cell separation, drug delivery, cancer therapeutics, cryopreservation etc.
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Dear all researchers,
Can we create a turbulent flow with the following conditions?
1- isotrope & non-homogeneous
or
2- an-isotrope & homogeneous
Regards,
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Hello
Isotropic turbulence means that there is no mean shear, rotation or buoyancy effects in the flow as this can lead to anisotropy.
Homogeneous turbulence means that there are no mean flow gradients.
In another way isotropy deals with invariance in rotation and homogeneity deals with invariance in translation.
Isotropic flows can have a homogeneous or non-homogeneous microscopic structures.
In many cases, the flow can be A homogeneous and anisotropic . The Homogeneous Anisotropic Turbulence (HAT) is observed in many problems, such atmospheric flows…
Regards.
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it may be Indian or other country aircraft. such as how much gain is required which specific frequency, dimension of foot print( as wings, cockpit, tail etc)
so that i can design a conformal array according  to given requirement.
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thanks ,
20 db for which application, mean for communication ,actually more than 50-60 antenna uses for a aircraft for different application.
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I am trying to simulate the Anti-roll bar mechanism in Nastran. I have got good results so far, meaning torque in the bar under rolling and no torque when leveled. During this the bushings of the bar were constrained in translational directions.
I want to transmit this force seen at bushing constraint to somewhere else. But the moment this connection is made and the constraint there removed, the force goes back to the suspension, making the anti roll bar ineffective.
I created this connection using a bar element having all 6 dof.
Can someone suggest a solution?
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Never Mind I solved it. But thanks for thee paper.
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Dear all,
what are the advantages/disadvantages of high compression ratio in engines?
Regards
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Dear Steffen,
the theory states that higher the compression ratio higher the engine efficiency. However, in real applications this is limited by the escessive combsution noise that can lead to excessive engine wear. In addition, for higher compression ratios, the combustion temperature will increase leading to higher NOx formation by thermal mechanism. The advantages and disvantages will be also related to the type of combustion that you will use. In general, for any combustion, the disavantages are that you are increasing the mechanical demand, forming more NOx and reducing your control on the combustion process whilst yo are increasing the thermodynamic effiency and reducing some pollutants as unburned hydrocarbons.
Best Regards,
Rafael
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I need to construct a 3D wooden bicycle trailer for Kids. The weight of bicycle trailers must also be light!
I don't know where I should start? I thought I'd start from chasis, but what criteria should I use to construct a chassis,Children's weights? no more?
The task says that the 90% of material must consist of wood.
Thank you
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Copy the principles of a car chassis to suit your needs.
Try to have a low centre of mass and a wide wheel track to help stability.
Use strategic, short struts to add torsional stiffness instead of using much larger sizes of wood.
Using some type of suspension component will allow much lower stresses on the frame but may be practically impossible.
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So far, different parameters e.g. Reflectivity, signal to noise ratio, power etc have been used to study PMSE echoes. Could any one suggest me the more useful parameter out of these three or any other they know ?
Thanks
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Depends what one plans to do with the PMSE data. For example, if goal is to investigate the wave activity in the summer mesopause region, probably Doppler velocity is the best to use. If one plans to do a statistical analysis about the phenomena itself, I do not expect big difference using SNR or volume reflectivity. Spectral width is used sometimes to highlight the turbulent areas in the observed region.
So, important is to define the interest of research whether assume PMSE as a tracer and use it to study dynamical processes or obtain background wind, or purpose is to investigate the PMSE morphology, micro-physics etc.
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Dear all,
I want to know that what is the reason of the usage of FEM in fluid mechanics. Isn't FVM better than FEM?
Why some softwares like COMSOL sill use FEM?
Is FEM has any advantages over FVM?
Which is better?
Regards,
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Often the simple answer is that depends on the "tradition" of the code.
Then, "better" is too general. We should focus on accuracy and computational cost and hence on the resulting efficiency. FEM is somehow less efficient than FVM for higly non-linear flows but recently DG method received new attention in the CFD community.
Finally, I would stress that FVM is nothing else that a FEM for a specific choice of the test-function.
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I am trying to create an impact pressure probe to measure spatial distribution of free stream pressure of a jet plume exiting to a rarefied medium. I found out that sankovich pressure probes is best suited for my purpose. Kindly provide the dimensional details of the above mentioned probe.
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I want to start a philosophical discussion and ethical debate on the reasoning behind why humanity should and must become a multi-planet species.
  • What do you think is the most profound and captivating reason(s) that you have to justify SpaceX and Elon Musk's goal of making humanity a multi-planetary species?
Elon said during the 68th Annual ISC on September 29th 2017:
"I think fundamentally the future is vastly more exciting and interesting if we're a spacefaring civilization and a multi-planet species than if we are not. You want to be inspired by things. You want to wake up in the morning and think the future is going to be great."
I agree with him here, but I think there is something more profound and captivating that must be addressed with regards to becoming a species that lives on more than just one planetary body. Other questions we may want to consider to help us reach this answer include:
  • What are the ethical considerations we must address before colonizing other worlds?
  • Do humans really deserve another planet to potentially ruin, or even sustainably terraform, if we cannot even figure out how to sustainably balance our own home world?
  • One might ask why doesn't Elon use his genius to create new technologies that will advance the human race by solving some of the Earth's worst problems?
  • Has he simply given up on this planet and does he therefore want a clean slate to build up from?
  • Does Elon think that technological advancements resulting from the drive to become a spacefaring civilization (i.e. propellant production via. CO2 sequestration powered by 100% solar energy systems) will eventually rebound to help the Earth?
  • Must we start colonizing Mars now (i.e. beginning in the year 2022) like Elon's timeline suggests? Potentially, if we wait too long, technologies to reverse climate change on Earth may not have advanced enough without the excitement of being spacefaring...
Lets see what everyone thinks about this, and let's keep it civilized in here. Try and get real profound!
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If i may add my 5 cents to this:
  • What do you think is the most profound and captivating reason(s) that you have to justify SpaceX and Elon Musk's goal of making humanity a multi-planetary species?
--> Depends how you want to see Elon Musk: as the visionary who wants humanity to thrive and improve? Or just as the one who seeks fame and fortune for being the first in doing things?
In my humble opinion, humanity has yet to reach a level of mindset to overcome cultural and religious differences. We might have satellites and smart phones, but in our thinking we still behave like cave-men.
For example, the Americans, when setting foot on the Moon, put an American flag there. Not one showing Earth. How would it be on Mars, when Chinese, Indians, Europeans and Americans set foot there? Whom will it belong to? For sure not the entire humanity, so we would just bring all of our archaic thinking into a new world. All our problems and issues, and soon the new planet will suffer all the same problems as we have on Earth.
As long as we do not manage to live as one humanity on one planet (i.e. having a global government), there is no point in making humanity multi-planetary.
  • What are the ethical considerations we must address before colonizing other worlds?
--> As mentioned above: if you want to colonise something, who does it belong to? Is there indigenous life (whether intelligent or not)? Or is it a barren rock?
Now given the barren rock case: Who does it belong to? Imagine it has a huge amount of rare minerals on it. Is it "whoever finds it can keep it"? In the outer space treaty from the 1960s, they addressed this topic, saying that space belongs to all humanity, yet not all nations have signed this and yet when it comes to mining/farming/inhabiting these space environments, how is that regulated? And if violated, who prosecutes the violators?
There is a huge legal issue in regards to occupying space environments.
Now given the planet is not a barren rock, but an obviously inhabited planet: Now we can either develop yourselves as species and not touch the ecosystems of these planets, leaving them pristine for the indigenous life. Or we can act in the human way and do the same mistakes as we did in the past over and over again and just go there, exploit and trash the planet until its depletion.
The most difficult and realistic case is actually the case of Mars:
Why is Mars so interesting? Because in its past it was very similar to Earth, it had a denser atmosphere, a magnetic field, volcanism, starting plate tectonics, liquid water and all chemical ingredients for forming life. Mars might have gone through a similar evolution as Earth, forming microbial life, or maybe even be the origin of terrestrial life, as interplanetary transportation of rocks after impact events is proven to occur. Now, Mars is the perfect (and maybe only) place to actually study how life on Earth could develop and if life could develop on other planets as well, if life is unique or if it appears quite common throughout the universe.
But, if we send now a bunch of colonists there, who will bring lots and lots of organic material from Earth, we might spoil Mars to a degree where we cannot study this anymore, loosing a very unique opportunity.
Given the case there is still life around, wouldn't it be best to first study it, before building houses, schools and hospitals next to it?
And then there is another ethical consideration that needs to be taken into account:
Sending colonists to space with current technologists would use up significant amounts of terrestrial resources. Sending just 30000 colonists to Mars would already use up all the remaining mineral oil reserves on Earth, not to mention the metals, materials, supplies, etc shipped with the settlers. In order to send these few privileged people to Mars, the rest of humanity will have to sacrifice their lifestyle, their future and their environment. Is that ethical?
  • Do humans really deserve another planet to potentially ruin, or even sustainably terraform, if we cannot even figure out how to sustainably balance our own home world?
--> If we could terraform Mars, why not first terraform Earth? Reverse the effects of climate change, stop and reverse desertification. Earth is better studied than Mars, but as long as here high-ranked people make money with pollution and deny scientific facts, nothing will happen for the better. The money that Musk wants to spend on the colonisation could as well be spent to cover parts of the Earth's desert areas with solar power plants, providing humanity with CO2-free energy. That would benefit more people.
Also, terraforming Mars will not be sustainable. Mars is loosing its atmosphere, because of the lack of a global magnetic field. it might become a home for a while, but thinking into the far future, Mars will be back to where it is now.
Plus, how do we know we can potentially manage to create stable living conditions on Mars, when we are all about destabilising every environment we enter?
  • One might ask why doesn't Elon use his genius to create new technologies that will advance the human race by solving some of the Earth's worst problems?
  • Has he simply given up on this planet and does he therefore want a clean slate to build up from?
--> Maybe because it is easier messing up something new, rather than fixing something old?
  • Does Elon think that technological advancements resulting from the drive to become a spacefaring civilization (i.e. propellant production via. CO2 sequestration powered by 100% solar energy systems) will eventually rebound to help the Earth?
--> Musk's rockets use RP1 (refined kerosine) like all other rockets, and as long as this remains the cheapest fuel, nothing will change. Rockets are basically 95% fuel that is burnt. Using synthetical fuels is a huge cost factor. And especially since the CO2-concentrations (despite being high enough to significantly influence the climate) in the atmosphere are too low for economical use, I do not see any of this happening any time soon.
  • Must we start colonizing Mars now (i.e. beginning in the year 2022) like Elon's timeline suggests? Potentially, if we wait too long, technologies to reverse climate change on Earth may not have advanced enough without the excitement of being spacefaring...
--> No. We need to politically, economically and ecologically get our shit together first. We need to all reduce our negative imprint on the environment on Earth, foster international collaboration not wars, fear or hate, we need to change our thinking not towards maximising the monetary output, but in maximising our own happiness and humanity towards others.
Also, we should (must) explore Mars first. The right step is to first send a small groups of astronauts to carefully study Mars (and come back) over an extended period of time (~20 years) to really answer all our open scientific questions, before we can even think of inevitably spoiling the pristinity of the planet.
==> this would be the right way, and would avoid many of the mistakes that human explorers on Earth have done in the past (i.e. settling at their first arrival to a new place)
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Analytical determination of pressures in the tooth spaces at the periphery from inlet to discharge
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You should consider every space as a volume between 2 resitors: the one supplies a flow fucntion of the pressure difference and the other leaks as well in proportion to the pressure difference. All the inter teeth spaces are in series and all of them between high and low pressure. Depending on viscosity you may have to consider as well in the gap between toth top and housing a transprt flow proportional to the sliding velocity..
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Generally after the calculation has been run and during post processing of results in either FLUENT or CFD-POST.
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Import the file to Tecplot, and probe several points on the shock wave and the reflection wall. Computer the angle by the coordinates(tangent function).
Best
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is there any other experimental method to determine the bending rigidity and shear stiffness of a sandwich (three-point bending test) outside Allen's method?
Allens method is described in his book "Analysis and Design of Structural Sandwich Panels" on page 258
Thank you
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Dear Zouhir, you write "But software only determined this according to the formula.
formula is: D= (E1*b* (d^3-c^3)/12"
Yes, this formula is commonly used for determination of bending stiffness of bars made of homogenious materials. Are you want to find analogical analytical dependence for determination of bending stiffness of sandwich bars as well for determination of shear stiffness of sandwich bars?
As for experimental technique,  I agree with Pouyan Ghabezi that three-point bending test is the simplest way to find flexural (bending) stiffness of a sample.
Good luck,
Serge 
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What could be the maximum distance that one can control a UAV from?
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I'd use commercial 3G-4G mobile phone networks in order to send and receive short communication lines that help upload discrete commands (eg. Speed, Altitude, Go to a preset waypoint, Cancel mission, Go back home....) and download basic status information. Wouldn't work for downloading real time imaging, but maybe acquiring some basic environmental information.
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 question - Write an script m-file to simulate in Matlab a step response (see help step) of the controlled system with K = 1 and  = 1. Tune the gain of the controller (K) until there holds that the overshoot of the system is 25 %. Show in your plot of the step response r(t), (t) and e(t).
During the last decade, satellites have become increasingly important. Telephone and television are just two examples of daily life applications.
A satellite has a life-span of about 10 years. After that, its components may fail or it may fall out of its geo-static orbit due to loss of kinetic energy. In general it will burn when it falls back to earth due to friction with the atmosphere (sometimes the satellite may not totally be evaporated which can cause considerable concern when nuclear material was used in the satellite)
Only a few places on earth are suitable for the launch of satellites by rockets or space shuttles. The weather should be favourable (clear sky, no wind, no clouds) and the political climate of the country should be "stable" and/or "predictable". This combination does not often occur in countries around the globe. Australia might be in this respect in an exceptional position. Therefore, it is important that engineers of Australia have some knowledge about rocket and satellite technology. In this tutorial we will focus on course control of a rocket.
The rocket (see figure 1) has an inertia of J = 1e6 [Nms2], a length of l = 25 [m], centre of gravity is located at 0.6*l from the nose of the rocket and a rocket engine that delivers F = 100e3 [N] thrust and can be changed in direction over angle  [rad] (in this tutorial we will only address this one-dimensional course control problem of a rocket).
The angle of the engine,  [rad], can be changed very quickly compared to the change in direction of the rocket,  [rad]. Therefore, the dynamics of the angle control of the rocket engine can be neglected; it can be assumed that the angle can be changed instantaneous. The size of the rocket engine can be neglected.
For control of the angle of the rocket, (t) is compared with a reference angle r(t). The difference e(t) is fed into a PD controller with a time constant of 1 [sec] (controller = K*(s + 1),  = 1 [sec]).
Figure 1, Course control of a rocket (one - dimensional)
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This site is not a platform for you to get answers to your homework. Try doing the question yourself and making concrete questions based on where you have trouble rather than wasting the time of professionals. 
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I am analysing flow over wing but I found out that at low angle of attack between 0 and 10, the lift coefficient is reducing instead of it increasing with angle of attack while the drag coefficient is increasing. I will appreciate if someone can tell me what is the cause.
I am a new user of Ansys fluent and to CFD 
Thanks
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The Y+ value depends on the turbulence model you are using. if you are using a turbulence model with a wall function then the Y+ value must be in a range from 30 to 100. However, if you are using a turbulence model, which doesn't need a wall function (more accurately, the turbulence model resolves the boundary layer) the Y+ value must lay in a range less than 5. Another point that must be considered here is the behavior of the fluid flow around airfoil at high angles of attack. because in this range the flow is an-isotropic and the Reynolds stress turbulence models are more favorable to be used. The usual two-equation models (such as k-e e k-w) fail to capture the fluid flow characteristics at high angles of attack, since they are based on the assumption of isotropic behavior of turbulence.
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Passive and active flow control methods have been widely used in aerodynamics for enhanced performance.But very few reports could be found on the application of these techniques to hydrodynamics. So my question is are these techniques applicable to hydrodynamic machines in which the working medium is incompressible fluid?
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analyzing using ansys fluent , i considered a 3000 iterations of K-omega turbulent model , but while exporting data , i got the value of cd and cl for each iteration till the end , my question is , which value of cd and cl ill consider  at the end ? is it the last iteration value , of at the steady unchanged values ?   
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Hello
I am working on design of NACA 63415 airfoil for my research.Besides computational methods,I am interested to do the profile mathematically.Can anyone tell me what is the chord length equation for a 6 series NACA airfoils.Thanks 
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I am looking for a research area in MPC control for the wind turbines for a PhD research proposal.  my background in instrumentation and control engineering, but I do not have enough knowledge about wind turbines. I am performing a research now by reading the recent paper about that topic. I feel overwhelmed and confused. I would ask people who have undertaken research in this area if they can suggest what a gap needs to be investigated?
thanks 
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You could check the National Renewable Research Laboratory (NREL) website for their current wind turbine research. Good luck. 
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Typically in Hypersonic Re-entry flows of Blunt Body objects and at an angle of attack which leads to the laminar-turbulent transition in the boundary layer on the leeward side(caused by roughness) which then causes flow separation in the afterbody flow.
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I am working on a space rover project, where the surface is supposed to be like Martian sand gravel mixture which has a static coefficient of friction as 0.6.
Now the weight of the rover is 50 kg and is being driven by 6 wheels of diameter 24 cm. The friction coefficient between the wheels and the ground is 0.58. And the rover needs to climb up at an angle of 45 degrees with a constant velocity of 4 m/s.
If any information is being left, please assume it as a variable x and help me finding the net torque required in terms of x to drive the system.
Please do mention whether you have found torque of a wheel or entire rover.
Please provide me with some rough values or a range of values where my torque requirements should fall on.
Please try to be more specific as I need to make it as perfect as possible in order to get the best results.
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I had to solve comparable problems to yours in my 100-level undergraduate physics course many decades ago. My course instructor was able to help me understand what was needed. I cannot imagine the underlying physics has changed since then. Have you tried asking at that level?
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I have the wake height and width behind a scaled down car model from a wind tunnel experiment. I am not sure how to compare the wake of this scaled down model with the actual body and get the estimated height of wake behind the car in actual condition.
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Dear Abhishek,
Ingo is right. Just let me add the following to his explanations: The validity of wind tunnel results obtained in testing of scale models is based on the fluid mechanics Principle of Dynamic Similarity [1] which states the following: "If two physical phenomena can be described using the same formulation (same equations and same initial and boundary conditions), the solutions for one of the phenomena are valid for the other one."
For the motion of air around and obstacle, this Principle guarantees that the non-dimensional results measured in a wind tunnel for a scale model will be the same as for the real, full-scale obstacle if the following conditions are fulfilled:
  • Geometric similarity: all relevant aerodynamic features of the real obstacle must be accurately replicated in the scale model
  • The Mach number must be the same for the model and obstacle: M = V/a = V/sqrt(γ·R·θ)
  • The Reynolds number must also be the same: Re = ρ·V·L/μ
  • Heat transfer (thermal effects) and diffusion can be neglected
And here is the big Dilemma: If the fluid properties for both the tests and real case are the same (i.e., same speed of sound (T), ρ and μ), and the scale model is smaller or larger than the real obstacle, it is obvious that it is not possible to have simultaneously the same M and Re as in the real problem. If we cannot replicate simultaneously both parameters, it is then necessary to choose which one will be kept similar to the real case. Generally, we choose the parameter with a stronger influence on the flow. For instance, roughly speaking M is dominant for supersonic flows (meaning that the value of M has a stronger effect on the behavior of supersonic flows than the value of Re) and Re for subsonic flows. Thus, for example, in high-subsonic testing, we would strive to work with the same Re as in the real case, and would not pay so much attention to M.
Effectively, this means that we are not complying fully with the requirements of the Principle of Dynamic Similarity. Fortunately, still the wind tunnel results can be useful. The only issue is that they have some error respect to the behavior in the real case, and we have to correct for that. Many researchers have characterized the Re and M scaling effects to be able to correct for this error when extrapolating the wind tunnel results to the real case. So, if the fluid properties for both your tests and real case are the same, you should try to work with a model as similar as possible in dimensions the real obstacle, bearing in mind also these recommendations [2]:
  • Blocking coefficient (ratio of frontal area of model to frontal area of test chamber): should be less than 0.1
  • Wingspan (or width) of the model: should be less than 4/5 (80%) of test chamber width
Hope this is useful,
Jose
[1]  White, F.M., Fluid Mechanics, 6 ed., Boston, USA: McGraw-Hill, 2003, p. 866
[2]  Barlow, J.B., Rae, W.H., Pope, A., Low-speed Wind Tunnel Testing, 3 ed., NY, USA: Wiley & Sons, 1999, p. 713
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Typically Hypersonic Afterbody flows involving blunt body re-entry vehicles(spacecraft) with an angle of attack and flow separation taking place in the afterbody flow.
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The RNG k-epsilon model is a good one for your case and make sure that you use and enhanced wall treatment to get a much better prediction of transitional flows
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Towards solving Auto landing  problem of a UAV what maneuvers carried out for heading correction along the runway by the autopilot. what are the path planning  strategies.
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two fundamental points here. One is to get the device tracking along the landing area, that could be by ILS but mos UAV operations dont happen on major civil airpors which are he only ones with ILS. SO you should use a sequence of waypoints, both lateral and vertical to guide the UAV along the lateral and vertcial landing paths . BU second point is just as important. In any crosswind you need o be able to Kick off drift so you dont strain the landing gear. Wing down only works provided the UAV can deliberately "sideslip" AND  the cross wind velocity component is limited by the into wind wingtip clearance- for most UAVs, So the crabbing technique should be used. This works for all wind strengths, but requires this Kick off drift manoeuvre to be performed just before touchdown- To late and you may smack off your gear To early and the wind will start to drift the UAV off the centreline. email me- I m a flying instructor   
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The idea is understand the influence between these three parameters on airplane.
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If you just want to illustrate the basic influence of configuration-parameters like stagger and distance between upper and lower wing on lift and moments of a configuration, then any simple 3D-Vortex-lattice code for more than one wing will be sufficient. The aatachment shows a sample for the estimate of the aerodynamic centre. OpenVSP appears to be too slow for a trend-study.
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Proposal for cooperation in the field of patent pending five types of new bionic wind turbines, Who is willing to cooperate?
I'm registering with 5 different types of Bionic Wind Turbines with the guidance of several university professors, I'm eagerly invited to work with those who are interested in this field.
In my opinion, the rules and equations for wind turbines (the Betz law (which is wrongly called the Betz limit), and ..., make the idea that wind turbine technology has reached its last stage, if creativity and Nature's inspiration can be two important factors in the remarkable improvement in wind technology! When everyone thought that everything was either zero or one (logical numbers), later scientists realized there was between zero and a logical infinite number!
Required expertise to work with us, piezoelectric, wind turbine, mechanical, electrical and aerodynamics.
With all kind of respect and humility,
Morteza Hadipour.
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Interested to know about the project.
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Hello, 
I have to realize a prototype of a patented invention of sea water dessalination using solar radiation. The performance of the engine increase when water move in small spaces. I need to know what is the limit to consider that we have conditions of nano scale in fluids flow.   I need also a good reference to assess the fluid motion at the nano scale and eventually a suitable software tool,
Best regards. 
Samir Touzani - Inventor
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So 50 nm of itckness of container space seems to be a limit where continum solution still work. . under this range i should apply molecular dynamics simulation. Thaks Henry
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Hello everyone !
I would like somebody who could help me in the comprehension of the trajectory of a particle in air flow with and without the presence of the Drag Force how the trajecotry is supposed to be ? I question people working in the field of <<Fluid Mechanics>> since I don't know myself that much about it.
I use for that the software Comsol Multiphyiscs 5.2 and I would be very grateful to you for your help.
Yours sincerely!
Imène Oualid.
 
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Dear Oualid imène,
   particle motion in a fluid flow it is not a trivial phenomenon, specially if we are dealing with numerical simulations. Basically the simulation can take in to account the interaction between the fluid flow and point-size particles in these ways:
0-way coupling: particles are simply tracers, and they follow the fluid motion without exchanging momentum or energy with the fluid flow;
1-way coupling: particles are influenced by the fluid, but not the other way round, see the paper suggested by prof. Filippo Maria Denaro or more easily https://en.wikipedia.org/wiki/Basset%E2%80%93Boussinesq%E2%80%93Oseen_equation;
2-way coupling: particles can also influence the fluid motion by means of a coupling term in the navier-stokes equations.
I don't know how comsol models the particles, but I guess it uses a point size model with either 0-way coupling or a 1-way coupling.
So, I guess that when you add the drag in comsol you are switching from a 0-way coupling to a 1-way coupling. When you do so, particles are not forced to follow the fluid motion but they have their own equation of motion: the fluid acts on them with a certain drag force and they move with a certain inertia.
Generally you should consider the particle Stokes number (https://en.wikipedia.org/wiki/Stokes_number) to decide with approach to use. If particles stokes number is very low, particles tend to follow the motion of the fluid so it is reasonable to adopt a 0-way coupling approach, if this is not true, you must consider also the drag force, or if relevant also the other forces in the Basset–Boussinesq–Oseen equation.
Visually, If particles are heavy they tend to deviate from the fluid flow trying to "escape" from the fluid vortex as a consequence their inertia.
Cheers,
Francesco
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I have been studying the applicable corrections. The aspect i want to clarify is when i know the wind tunnel Cd min of aircraft and i calculate the drag ratio using  the skin friction coefficient and form factor and interference factor at test and flight reynold numbers. what geometry i use for these calculations . Either aircraft or wind tunnel model geometry. What i think is that we are using the ratio of areas so it does not matter, we use the model or aircraft geometry. Can anybody elaborate this.
i have extracted this equation from a paper. Why the author hasn't used here the FF, IF factors.
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Both approaches are valid.
Approach 1: scale by skin friction ratio. Best suited for components (you have to apply it to the fuselage, wing, tailplane... you are talking about the entire aircraft, but you can calculate the form factors for each component, not for the entire aircraft. At least you may guess what percentage of drag is due to each component - in this way you are assuming a drag breakdown and including the aerodynamic interference in each component).
Approach 2: very similar to approach 1. In this case you are dealing directly with the CDmin. It seems best suited for airfoil and wing. Faster than approach 1.
Approach 3: get wind tunnel data at different airspeeds and extrapolate CD min from your experimental data. Best results if your tests are at Re > 1.5 million.
Source: Barlow, Rae, Pope. Low-Speed Wind Tunnel Testing. Wiley, 3rd edition, §8.3.
Which is the best? The truth no one knows, except flight testing, but at that time you have measured what you want to calculate now. And the flying aircraft will be certainly different from the wind tunnel model.
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By inward inflation, I mean vacuum inside the membrane (such as a cylinder with closed ends) leading to its crushing by atmospheric pressure.
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A membrane theory is not suitable in this case since a membrane cannot support compression. Therefore, what you want is an elastic shell or a cylindrical shell. The case of a cylindrical shell under pressure is known and leads to build-up of compressive stresses. Crushing will depend on inhomogeneities and is much harder to predict. Similarly the crushing of an elastic shell is a difficult problem. Recent work by Thompson  and Hutchinson on nonlinear shells under pressure is relevant for you.
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Can I model a propeller as a turbine just by changing the value of coefficients like loading coefficient, thrust coefficient,etc to negative given that they rotate at same RPM and have similar flow conditions. I went through some resources online and they followed a similar approach of actuator disk just like they did for wind turbines. The only difference I saw was things getting reversed, i.e. the stream tube getting narrower downstream,etc. Please help
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The underlying theory is the same, the applications are different.  Having said that I recommend that at least you compare the difference that the two densities (air and water) impose on them.
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The flow downstream of a wind turbine has rotational flow, however I wish to convert it back to axial flow to as greater degree as possible. Any literature regarding the topic would be very helpful as well.
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Vedant, short answer, yes you can and it is done routinely in turbo-machinery. In terms of what features and parameters (chord, M, incident angle, exit pressure, etc) to consider, and for literature search, I would suggest to lookup "outlet guide vane." This is designed to achieve de-swirling of the flow exiting a machine, before the flow stream can be diffused effectively and exhausted into the atmosphere.