Aeronautics - Science topic

Dear Prof. Lev Kurlapov,

Thanks for your suggestion but it's not related to one....

In brief, I am seeking "Onboard Triggering using Accelerometer during Captive Flight Testing".

Regards

Mostak Ahamed Thank you

please send a short outline of your research and course material, Aircraft Manufacturing Management. I will give you a few comments, but may not have time to provide a detailed response.

For an entire wing, the reference area is usually the projected area from the top view. If you take just the tip my suggestion would be to parameterize the results for a certain range of the wing reference area (if the winglet has a defined dimension)

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It is really difficult to suggest the business model to diversify their business during the Corona pandemic period.

These Air Navigation Service Providers are rendering their duty because of the air travellers movements from one place to another.

Even the existing business are getting deteriorated in all aspects. These people don't know except this services.

They can do some Cargo services which will support the Marketing dimensions.

There is a huge demands for consumable goods and services so that is the correct if way if concentrating during the pandemic period.

I don't have any idea or any business model suitable for them. Sorry.

The article is just click-bait; if somebody doesn't understand how the lift is created he/she haven't developed the most basic concepts of fluid dynamics. I'm trying to explain how the aerodynamic forces are generated around a body; excerpt from a course I'm working on:

"According to the kinetic molecular theory of gases ... static air exerts a pressure of about 101kPa on any object at sea level, created by the collisions between the object’s surfaces and air molecules ... this pressure changes when the air is not static but it moves around the object ... the random movement of the molecules changes, their random speed vectors gaining a component induced by the macroscopic air movement. ... This change of the random movement of the molecules is causing variations of pressure in the air volume, and acting over the object surfaces are creating forces, termed aerodynamic forces."

The article focuses on inability of common layman "lift theories" to account for the decrease of pressure and speed increase on the upper wing surface. I'm trying to correct this using some common sense.

Let's imagine a flat barn door (our "wing"), flying at an angle, through static air. Let's imagine the air molecules are un-moving grains of sand as a first approximation. In such a case the wing interacts only with the "molecules" that is able to hit, in the direct path of the wing. On the top region, the "wing" is not interacting with the "molecules", a void is created between the "wing" and the "molecules". This model is called "Newtonian sine-squared law of lift" and developed by - Newton in 1687. Interesting fact, this model is not at all accurate for normal flight, but it is accurate at hyper-sonic speeds and/or very low temperatures and pressures, such as space vehicles re-entry, as the molecular speeds are much lower than the aircraft speed.

Well, let's replace now the grains of sand with air molecules that are moving, according to the kinetic molecular theory of gases, at typical air at room conditions, the molecules are moving at about 500 m/s. A wing flying e.g. at 100 knots, about 50 m/s, is much slower. The void between the wing and the free stream is quickly filled by air molecules that are "pushed" in by elastic collisions with other air molecules. Since the air molecules are moving in the void in a global downward general direction, this has a macroscopic effect of increasing the airspeed. Since the total kinetic energy needs to be conserved, less molecular speed is available for collisions and that accounts for decreasing the pressure over the top of the wing. According to Bernoulli this is correct, as Bernoulli law is an energy conservation law, as applied to fluids. Since accelerating air downward is creating an upward lift force , the Newton's second law is also correct. So Bernoulli's and Newton's laws are actually the interpretation of the same physical phenomena.

Hopefully this short introduction dispels some misconceptions of how "no one can explain lift"

I think Aerospace industry is at a beginning of a complete transformation. A lot of tech startups are trying to capitalise on the premise that what is happened in the small consumer drones in the past years will continue on a bigger scale on manned aircraft, with the development of "urban air mobility" and "advanced air mobility". Startups like Joby, Lilium, raising USD 720M, and respectively USD 376M demonstrate plenty investor interest in the subject. Stunts like Zapata's Flyboard Air and Daedalus Mark 1 are capturing people's imagination, as well as plethora of manned multi-copter project that is bombarding media lately. A lot of pertinent people and organisations are thinking the technology is at the point where it permits creation of personal air vehicles to transition from everyday driving to flying. Everybody wants to be the first, but I think this is much more complicated than sticking a bunch of electric rotors to an air-frame.

A VTOL aircraft has conflicting requirements for the parameters that drives cruise and hovering performance: L/D drives the performance in cruise and that means large aspect ratio wings, low wetted area, careful design to minimise drag, and a small propeller size. Disk loading and no flow interference drives the hovering performance and that means large rotors and no wings. Actually, only 2 basic VTOL designs have evolved to 'life' over the last 50 years of experimenting and testing, and those are military aircraft. These are the V22- osprey - tilt-rotor, and harrier/F-35 - jet VTOL, the military specification aspect to perform the mission are the reason of their success, the economic cost is secondary.

The civilian marked is driven by economics, and as long that the aircraft design compromises too much, it will never be a viable option. Some people believe that the electric propulsion solves the problem, because of the high inherent efficiency, distributed propulsion and other effects, but a hidden aspect that kills the efficiency is the aerodynamics of VTOL. If the aerodynamics is not right, you end up with an inefficient aircraft, that only exacerbates the unwanted characteristics of electric propulsion - the weight and low specific energy of current batteries. I don't think the hybrid power generation, as hydrogen fuel cells, are the right solution either, it just increases the weight and complexity with marginal gains. It's much better to concentrate on the weakest link in the whole chain and that is the aerodynamics of VTOL flight. Current battery technology are good enough to develop today aircraft with ranges to cover average commuting distances.

I'm not a fan of UBER's proposals either. They want 6-8 passenger "air-taxi" style VTOL aircraft, flying between city vertiport hubs, so they can capitalise on the whole route, from driving to the vertiport, flight to next vertiport, drive to final destination. My opinion is that from the passenger perspective is much better to fly directly "door to door" with smaller personal aircraft, you eliminate driving, hub transition, boarding and waiting times. Not to mention you eliminate huge vertiport hub infrastructure that needs to be developed and maintained. Small sized aircraft can land in small spaces, why not develop standards for small vertipads that can be installed everywhere, from personal driveways to supermarkets and local grocery stores.

Royal Society Applied Aero conference

Refer this article. Its most read

Brelje BJ, Martins JR. Electric, hybrid, and turboelectric fixed-wing aircraft: A review of concepts, models, and design approaches. Progress in Aerospace Sciences. 2019 Jan 1;104:1-9.

Is this what you are looking for? https://doi.org/10.2514/5.9781563479854.0039.0049

You can't build an elevator to the ISS at 400km, because at this altitude the orbital rotation speed is not the same as the earth rotation speed. Furthermore, the ISS orbit is not on the equatorial plane.

The idea of Space elevator is conceivable only in the equatorial plane and does not really make sense elsewhere.

There is a big drive into lightweight materials i.e. composites, aluminium, etc. As Emmanuel has mentioned additive manufacturing is big on the agenda. The lightweighting is mainly supporting hybrid and electric powertrains. These powertains are heavy, so to reduce weight and increase range the industry is looking at lightweighting.

I suppose with motorcycles it will be similar. I've seen a motorcycle manufacturers also developing electric powertrains. So again, lightweight materials would be good. Most people tend to concentrate on the frame. However, how about reducing the weight of the engine (if keeping internal combustion) and look at reducing the weight of components such as suspension, etc.

We have developed EFIS/GNSS aircraft satellite tracking system that can satisfy ICAO GADSS . http://www.sciencepubco.com/index.php/ijet/article/view/21320 .

We (UPNM/Worldgate) through university industry collaboration shall try to certify it as TSO so that it can be fitted to civil aircraft. .The sensors consist of 9 axis (accelorometers /gro/magnetometers) and GNSS(3D) that are telemetry to servers via iridium/gsm and short range IT devices via WiFi. Its not only provide tracking capability but also EFIS data except we don't install air speed since we want to be independent of aircraft system.

Crew Resource Management Concept is relevant for proactive safety awareness in critical situation management team communications scenario. This covers human factors of culture and individual team member power bases interaction in crisis management teaming. The opposite of CRM is 'Captainitis' , where the leader flies on using his /her own human error fallability only , and ignoring crew advice, help and oops alerts from crew. Detailing for that CRM was once included in training syllabus on International Helicopter Association ( IHA) (Canada) website for pilots and flight crew training and audit in low flying in the wire risk context . I would suggest a maintenance team in crisis is an extended flight crew when maintenance impacts on mission . CRM usually helps /applies in all human crew critical incident situations ?

Surveying burn areas, fire movement, damage/impact. Looking for survivors.

It depends a bit on what aspect of the fire-fighting you focus:

- For the assessment phase, typically quite standard UAV's are used. These are typically sturdier models that feature a short deployment time and are often also used by civil protection, police, ...

- For the fire-extinguishing phase, purpose-built solutions do exist, e.g.: https://www.aerones.com/eng/firefighting_drone/

Check cfdonline, linkedin and researchgate

I would look on line for the Strouhal number of similar structures at similar Reynolds numbers to see what is already been done. When in doubt 0.22 is a good first guess at the Strouhal number. From there I would set up an excel spreadsheet with different heights above the base plane, then do a 1/7th power law for the boundary layer effect and calculate the wind velocity in 10 or so different points up the height. From there you should be able to get the vortex shedding frequency as a function of wind speed and height to compare to your structural resonances. Figuring out the unsteady lift force is more problematic from first principles but I bet there is a lot out there in the published technical literature. Good luck

Hello Mr Ishan, You will have to specify the material and then search for compatible lubrication oil that are non corrosive for that material. Usually the material used is steel alloyed with molybdenum, Magnesium, copper aluminium etc, in many bearings. I have worked with OX-27 oil on APU engines, which have to be drained for engine preservation, and we use OM-11 as the preservative oil. If you see bearings used in aerospace applications, many bearings are made from vacuum-melt 52100 or VIM-VAR M-50 steel and are normally manufactured to ANSI/ABMA

tolerance class 5 (ISO class 5), with high-strength machined

cages. You can refer NASA TM 102529 on steel bearings used in aerospace applications. Hope this information is useful.

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.

Hope this helps!

Tomasz, the observation of this signature in the absence of pertubations of the other axes strikes me too. If there had been gravitational forces - or even regular engine corrections, you might have expected pertubations on at least two axes. Therefore I strongly suppose some artifacts in the measured orbital data.

Dear Herve, I'am interested on your topic: do you have a paper/document on theorem's proof? Thanks.  Gianluca

I need to design an aeroelastic model of a tensile structure (hyperbolic paraboloid cables net and membrane). The natural frequency, damper and mass are fixed using the aeroelastic scaling laws. These laws fixes frequency ratio, damping or wind speed ratio. However, generally, they are used for buildings very different from flexible roofs.

سلام.متوجه سوالتون نشدم

By compacting pressure and sintering temperature , we can obtain different alloys made from Ti  with addation metal such as Ni , zro2 ..etc .this alloys is used as a biomaterials such as stent in catheter or dental post .

I am more familiar with KM and KBE concepts that are being used in Aeronautics Industries for product Design and Development. Here are few papers/ application examples. Take a look.

Hallo Jeremiah,

Normally, the Re is the tip Re in the wind turbine simualtions therefore,

Re = (Roh*tip_Speed*L)/meu

Roh and meu are the air properties at the inlet

L is the blade chord at the tip

tip_Speed = sqrt(Uinf^2+(omega*R)^2)

where Uinf : is the free stream velocity   (known)

from the tip-speed ratio you can calculate the (omega*R)

(omega*R)=tip-speed ratio * Uinf

I hope that might help you

Best regards

Mohamed

Dear Sir

Thank you very much

Thanks for your reply. It seems that the problem was a x,y component of flow direction.  I rotated the compudational domain for each degree i  wanted to study and at the boundary conditions, i inserted at the inlet, velocity in x direction only, (which is vertical  at the inlet). See below my results. 

Hi Paulo,

You might find the following two references helpful.

Rogalski, A., & Chrzanowski, K. (2014). Infrared Devices and techniques (revision). Metrology and Measurement Systems, 21(4), 565-618.

McManamon, P. F., Watson, E. A., & Eismann, M. T. (1998, March). Suggestions for low cost multifunction sensing. In Aerospace Conference, 1998 IEEE (Vol. 1, pp. 283-307). IEEE.

I agree with Naceur's input on specifics - looking, for example, at HALE type fixed wing UAV, 1/2kg seems no challenge at all...

Nevertheless, in general, I would focus on three main aspects to derrive at load carrying capabilities:

- size (larger lifting surfaces whether as wing or rotor usually translate into more lifting capability)

- speed (higher speeds allow higher lift production, all other parameters considered fixed; again, in general, it doesn't matter whether fwd speed of a wing or rotational speed of a rotor)

- propulsion (the two points above directly will affect drag which in turn will require excess thrust to overcome)

Hope that helps at the conceptual level

For your maximum value (for example 34 dB or 15 dB, or -5 dB) you must define the value 0dB. From this maximum value (34dB, 15dB, -5dB) then decrease value 3 dB and you will get the value on level -3 dB, it means (31dB or 12dB or -8dB). On these values (31dB or 12dB or -8dB) then you define searched frequency bandwidth.

You may find these articles helpful:

Dear Mr Wild,

your answer is very valuable, thank you, I will stick to it.

Kind regards!

Graphs or contours? 

If the aspect ratio is low then secondary loss and tip leakage loss have a greater percentage effect and the efficiency falls. However the low aspect ratio blades are relatively stiff and forced response and flutter are less likely. With high aspect ratio the blades become floppy and their resonant frequencies fall flutter is more likely to occur. Also high aspect ratio blades for te same duty as low aspect ratio blades have much smaller aerofoils and therefore Reynolds number. This leads to thicker boundary layers and tends to lower efficiency. The number of leading edges and their blockage is changing too. So high aspect ratio leads to lower efficiency and more vibration. Too low aspect ratio has low efficiency and requires greater axial gaps to avoid forced resonse issue.

Hi Arun,

By saying ODB, I assume you are using Abaqus to generate your results as the ODB file. If so, then you have the functionality to import back the ODB as a new model. (See first picture) You can then edit the elements.

Also, you have the option to import them part-by-part in which case you could import deformed configurations as well. (See second picture). Once you've done it, you can again remove or add elements as you wish.

I hope this helps! There is a blog post at Intrinsys, listing the part import functionalities of Abaqus here: http://www.intrinsys.com/blog/2016/importing-parts-into-abaqus-cae

If you are looking for more help or tips/tricks regarding Abaqus and CATIA, look around the blog, you will find a lot of useful information!

Best regards,

David

Thanks, John, for the remark on pressurized and/or cryogenic testing, since this is the only way to get Mach and Reynolds number similarity for down scaled models - unless you change (theoretically) the flow medium (e.g. a water tunnel gives you easily Reynolds number similarity - but no Mach similarity except for real incompressible flows at M<<0.1).

Nevertheless, if you are limited by the available wind tunnel facility, it is probably more important to match the Mach number similarity and accept that you will measure higher friction forces (drag) than to be expected for the real aircraft. There are some extrapolation methods around (see some AGARD reports on wind tunnel testing) to estimate the drag variation. When it comes to flow separation the situation gest more complicated, although proper transition tripping will help to eliminate low Reynolds number artefacts. Anyhow, these measurements will not give you absolutely accurate values, but e.g. to compare designs it is mostly sufficient.

One remark to the answers above:

@Aziz: your comment may hold for bodies where the drag is mostly related to pressure drag only. For bodies where the drag is dominated by friction forces, your comment that CD doesn't significantly change between Re=1000 or Re = 10 mil. is definitely wrong.

I could not get how the impact is made. One reaason for lesser time indicates damage to the structure opening higher no. of defect sites or longer when the impact compresses the pores and allow only slow ingress requiring long time.

Anyway, a detailed picture will be more helpful to answer better.

MD11 and F117

but the heavier plane needs more accurate, complex and cost fortune safe operation system

Dear Sir

I am attaching a paper.

with regards

Y D Dwivedi

I am researching in the same issue

For digital implementations, I just stop integrating the error signal if the controller command signal, i.e. the input to the combined plant/actuator, saturates (i.e. hits +/- max). I know there are more sophisticated approaches, but I have always wondered why anything more than this is needed (?). 

My suspicion is that 1) the small radius rotor would have to rotate at an unacceptably high rate to counter the torque by the main rotor, 2) the resulting turbulence would likely affect the performance of the main rotor, and 3) it would be a very wasteful design, as the small rotor would not contribute at all to lift, so all the energy spent on making it rotate is wasted.

The reason why the standard helicopter design works is because the small rotor is at the end of a large moment arm. The reason why the coaxial design works is because the two counterrotating rotors both contribute to lift.

;O)

... I mean, concerning efficiency, there is nothing better than only to use your battery, without such an onboard charging system, but we also know that there are restrictions with payload, flight time and so on and it really could be useful to think about it. Maybee there is a possibility to slimm your plattform to extend flight time and range...

 If you did not find the following link bevore, have a look at it. Maybe, it could help:

Also in an rc-forum discussion in Australia they linked the side: But I am sure you already could find this. Nevertheless, the link:

 There is also a discussion about the topic in a german rc – forum. There are some interesting ideas, but all in all they are not convinced by the idea: There would be much professional development to do to get an effective system...

Jetcat has integrated a small generator to charge the systems batterie, but this will not help you if your copter would not be driven using a jet-engine. But maybee here you can find proposals/stimulations for own ideas:

In my group we also use rc helicopters, but we never did fly such a long range mission. Also in germany it would not be allowed to fly out of sight. But the mission you describe would be perfect for a petrol or jet driven Helicopter System. It should be possible to fly your mission with such a platform. But you would have to develop and configure such a system especially for such a mission, you also need an excellent pilot and as you mentioned, this also would be an other platform again, spend lots of money and so on…

Mybee you can find some better hints at the links and if you would find a solution, please keep me up-to-date.

With best regards and good luck for your realy interesting mission...

Patrick

I am waiting for your responses.

If you considered a spring, it will be like considering the elasticity of the structure. In that case based on your BCs an ICs, you could observe damping or diverging or self-sustained response (flutter). But as @Fulvio_Sartor said buzz is related only to ailerons vibration. 

Hi

You can find these data in the links below:

Nonelectronic Parts Reliability Data

Electronic Parts Reliability Data

But you have to pay to access it.

 

As an Air Traffic Controller, I like my instructions to be understood by the pilots. If both of us are going to follow different languages as a medium of radio telephony, then imagine the confusion! Already we are facing the problem of phonetics and different pronunciation among all the stake holders in aviation like pilots,ATCOs and ground crew.The use of non-standard procedures and phraseology can cause

misunderstanding. Incidents and accidents have occurred in which a contributing

factor has been the misunderstanding caused by the use of non-standard

phraseology.

The worst accident in aviation history i.e.,Tenerife collision between two B747s on 27/03/1977 was due to non standard R/T only. So standard and uniform R/T is a must for safe operations. Language was a part of important factor in many accidents like Milan Linate airport MD10 and a Cessna. etc

Follow the link to know about the english tests satisfying the ICAO SARPs for Language proficiency requirements.

Regarding the air traffic through out the world check ACI (www.aci.aero) or IATA (www.iata.org). They are publishing the air statistics regularly in their sites.

If you feel I may be of further helps,please inform me.

Regards and best wishes.

number of articles on the sub. question are available. interested person may refer to it to understand the solution thoroughly.don't look for short cuts.

ADS-B. But not all aircraft have it.

Did you have a look to the benchmark problems used for the computational aeroacoustics workshops? They are available on the NASA Technical Reports server. There are different test cases of increasing complexity. Analytical solutions are usually provided as well.

Hello Green

This is my collection of aeronautical books:

I hope it will be helpful.

Pass : Lahidjan_Sadatmahalleh

HI,

Peter pointed us towards the answer to this problem. The W/S will depend on the main function and performance of the aircraft - speed (cruise, on function, take-off, etc). As an illustration, a steady flight with low gust sensitivity would requires high W/S. But this would mean high take-off and landing speeds.

Meaning, there is no short answer to this question. Torenbeek do give a method to arrive at compromise best.

Wan Zaidi

I usually get good results using following simulation configuration in my experimental validations (where I use C language funtions): In your Simulink diagram, menu Simulation/Configuration parameters; Solver options, Type: Fixed-step, Solver: ode1 (Euler), Periodic sample.. : Unconstrained, Fixed-step (fund. sample time): 2e-6, Tasking mode for periodic sample times: Single Tasking. Then I use 2e-6 as a simulation sample time and about 1e-4 or greater for the controllers and estimators (previously dicretized).

Ramjet belongs to air breathing engine and inparticular, in the category of steady state combustion.In case of ramjet, air with supernsonic speeds gets compressed by supernsonc and subsnoic diffuser by means of shock waves,  mixed with fuel from injectors, ignited by means of ignitors so as to develop sufficient pressure and temperaure casuing combustion to take place and combustible products expanded through nozzle producing necesawry thrust requried to propel jet engine. Supernsonc combustion is not possible as air must have sufficient pressure and temperaure for combustion. KE of the air gets converted to pressure energy so as to cause necessary combusiton. Compressor and gas turbine are eliminated in this engine, and diffusers are provided.  .   

it was long back in 2007-2008. Better is that you disclose some details or ask some specific queries otherwise beating around the bush will fetch nothing

I can't believe NASA is funding this before having established human settlements on other solar-system bodies with a less ambitious but much better understood propulsion technology, namely nuclear power.  Warping space to any practical extent would probably require extreme energy densities that only nuclear processes - and lots of experience manipulating them - can provide.

I don't know much about the other sims, but X-Plane lets you access simulation data via UDP. Two of my students wrote an interface which we could use to get sim outputs and write sim inputs. The number of accessible states / parameters is fairly comprehensive.

You'll find information about the protocol at http://www.nuclearprojects.com/xplane/xplaneref.html

Cheers,

Marc

You can divide the pressure distribution around a body such as an airfoil into two region beginning from the leading edge.

In the first region near the leading edge the pressure begin with a maximum value at the stagnation point then decrease up to a minimum value, while the airflow velocity increase along the surface. This is the favorable pressure gradient region (dp/dx<0). There is no risk of separation in this region

After a minimum point the pressure begin to increase along the surface, while the velocity decrease. This is the pressure recovery region, or  unfavorable adverse-pressure gradient region (dp/dx>0). In this region there is a risk of separation if the pressure gradient is high enough. After a certain point on the cp(x) graph in this adverse pressure gradient region if there is a constant pressure region, this region may be an indication of separation. However this is not so clear. Therefore it is better to calculate the boundary layer on the surface, then evaluate if there is a point where Cf is near zero.

While very early aircraft were fitted with constant pitch propellers, modern propeller aircraft are fitted with variable pitch propellers which accomplish the following:

Adaptation to aircraft speed

Reverse used at landing

In case of engine failure propeller is feathered that is, oriented along the velocity so that it does not rotate. For that reason when one of the engines of a propelled aircraft fails one of the first procedures to apply is to feather the pitch. Failing to do so keeps the propeller rotating and when piston engines are concerned the compression of the cylinders represents a considerable resistance to its rotation and this adds additional drag. This is not the case with turbine driven aircraft in particular when the propeller is driven by an independent turbine stage(s) called free turbine in which case there is much less torque resistance.

When the crew attempts to re-start a piston engine they just un-feather the propeller which causes the engine to rotate again and thereby eventually re-start,

The following thesis may prove helpful to you:

T.V. Marcard, Design and implementation of an attitude estimation

system to control orthopedic components, M.Sc. thesis, 2010:

I have seen few solutions solved by NASTRAN CFD package. It may be useful for you.

Dr.S.Ravindran

Try this one:

Comsol - Heat Transfer Module

Which kind of oxygen mask do you develop : for fighter aircrafts ? safety oxygen mask in commercial flights ?

Mr. Kumar, I think I have found an answer to my problem.

When I define zero velocity, there will be no turbulent viscosity. Because turbulent viscosity is a result of velocity. So no velocity means no turbulent viscosity.

Since turbulent viscosity ratio is the ratio of dynamic viscosity and turbulent viscosity, they both must have values other than zero. I don't exactly know which parameter is in nominator or denominator, but if one is zero and is in nominator, then the ratio will be zero. Otherwise, it is infinity.

In my case, I think, denominator becomes zero and the ratio goes is infinity.

I must say that I am not an neither expert in the subject of turbulence nor in fluid mechanics. So, my answer is not more than an idea.

Dear Sir, r u having any Docs For finding temp red factor?

Good points above. In practice what you need is to reparametrize by arc length. Rick Parent's animation book covers this nicely. A numerical approach is to build a table of arc lengths using a linear approximation. Small steps in the parameter 't' give points on the curve. Calculate the linear distance between each pair and enter the total distance travelled in the table as (Euclidean) distance against parametric distance. This can be normalized by dividing by the total distance to give a 0<=d<=1. Given t the distance can be found - use linear interpolation to find a distance between table parameter values and vice versa. This is an approximation whose accuracy depends on the step size. In Rick Parent's book there are various ways of controlling velocity and acceleration along the curve once arc length is known, but sow-in slow-out is most common in animation, often done with a cubic.

The below 2 tutorials may not be exactly matching your requirements - Still both will be useful to you I guess

Unless there is specific research looking at the effects of debris/precipitation damage, you're more likely to find relevant resources within maintenance documents or accident reports where such events have been reported. For example, search "CASA propeller stone damage" for relevant information in the first listed article from the Flight Safety magazine. At the more severe end of the spectrum, an academic at Loughborough University has researched the aerodynamics of battle damaged wings, which may have some relevance to your proposal - search the AIAA database for related papers.

Hello,

Jameson did a numerical optimization using adjoint method. So this means he modified the original airfoil which is not shock-free at these conditions, so the results you obtain may be fine. See Harbeck, Michael, and Antony Jameson. "Exploring the limits of shock-free transonic airfoil design." AIAA 43rd aerospace sciences meeting and exhibition. 2005.

Regards

François

A Cessna 172 has no anti icing system, as long as i remember a electrical pitot heater for preventing freezing over the pitot tube and a carb heater for preventing formation of ice in carburetor are the only two ways to prevent ice from forming; for that the C172 cannot flight in cold weather conditions.

There are two common types of anti ice systems: the electric thermal heating system and the bleed air (pneumatic) system.

The electric thermal heating system are most commonly used on windshields and propellers. The bleed air anti ice systems is used by most jet aircraft to prevent ice from accumulating in leading edges and flight surfaces (this air is taken from the engines or an independent compressor unit).