Fluid Dynamics

Fluid Dynamics

  • Dan E Kelley added an answer:
    Does anybody work with the Gerris Flow Solver?

    To communicate about important difficult issue related to Gerris

    Dan E Kelley · Dalhousie University

    Yes, all sorts of people do.  If you state your actual problem you may get some help.

  • Olivier Minazzoli added an answer:
    What do you think about the peer-reviewed fully open access encyclopedia: Scholarpedia?

    Scholarpedia is a peer-reviewed open-access encyclopedia written and maintained by scholarly experts from around the world. Scholarpedia is inspired by Wikipedia and aims to complement it by providing in-depth scholarly treatments of academic topics.


    Olivier Minazzoli · University of Nice-Sophia Antipolis

    Dear Werner,

    I don't understand why you say that, because one has to be invited to write an entry, scholarpedia doesn't deserve the name of encyclopedia. As a matter of fact, all encyclopedias work this way (except the very special case of wikipedia). For instance, in the 13th edition of Encyclopaedia Britannica (published 1926), Sigmund Freud wrote "Psychoanalysis" and Albert Einstein wrote "Space-Time". The idea is to do the same with today most acknowledged researchers in their field, except that it would be free for everyone. Isn't it a marvelous idea? (which doesn't mean that it is problem-free)

    Regarding citations, I don't see why citing an entry from scholarpedia would be worse than citing any other review paper. I don't talk about wikipedia. Wikipedia is not the scope of my original question.

    But I agree that they might be a formatting issue due to the wikitext format. This may evolve in the future though. However, I disagree with the redundancy issue that you raised, as it exists in "classical literature" as well. (Again, I am only concerned by scholarpedia, and not by wikipedia).

  • Ahmad Odaymet added an answer:
    Is there any relationship between the inter facial tension and the surface tension of liquids?
    The surface tension of liquids can be easily measured. Whether we can calculate the interfacial tension between two liquids from the surface tension of them I am unsure and require some advice.
    Ahmad Odaymet · Alfa Laval France

    I would advise you to check the sites below:





    You can also find some interesting information from page 11 to page 14 in my book: " Condensation Dans Un Microcanal En Silicium: Etude Du Transfert Thermique Local Et Identification Des Structures D'écoulement ".

  • Jeeva Balu added an answer:
    What are the reasons for being able to capture neither velocities nor post processing velocities, from a shadow graph image?

    We recently captured shadow graph image of spray, only diameter was post processed, velocities was not post processed. We used lavision to make a shadowgraph for our experiment. We have captured a double frame image of spray with a double frame background image for post processing in the lavision software.

    Jeeva Balu · Indian Institute of Technology Bombay

    Thanks Philippe leick  for your reply.

  • Ioan Sorin V Leoveanu added an answer:
    Hello dear, How to model the forces exerted by the water wave,any help is appreciated
    The object (horizontal capsule) is floating on water actually I want to get the capsule dynamical equations , Then solve it and get the speed and acceleration,Wave velocity and wavelength and frequency is known
    Ioan Sorin V Leoveanu · Universitatea Transilvania Brasov

    Oly in that last day i see the schetch of the problem you need to solve.  In the first intervention i believe that you want to compute the loading system on civil engineering construction subjected to flood or other damages. In that moment all is clear, if you want to keep horisontal the "structure" you must analyze the systems for houle effect diminishing that is common on passagers naves. Principally there are 3 types, the system based on wings automated command,  the system based on giration reaction and flooding room system. The geometry of the sheep influences only the values of that reaction forces and you will find a lot of papers about that. The Journal of Marine Science and Application publish some good researches in that area. I believe that you will be satisfy from that answer. You will see that almost studies that you will find are based by authors own software developed over the commercial used software.

    Kind regards and Good Chances.

    Ioan Sorin


  • Radomir I Slavchov added an answer:
    How do you measure the contact angle of water on an oil surface?
    Additionally, does the contact angle change for water on oil surface and oil on water surface? thank you.
    Radomir I Slavchov · Sofia University "St. Kliment Ohridski"

    You need to measure two angles: water/oil/air and oil/water/air. They should be both independant of geometry (no matter if it is water lense or oil lense), in the ideal case. Normally, the impurities are making things more complex, and since they are partitioning differently for oil lense in water and for water lense in oil, you will get different results. If the denser fluid is forming the lense, it may sink or it may not sink depending on the three interfacial tensions. The condition for a small lense not to sink is sigma12 < sigma23+sigma13 (small compared to capillary length; 12 is the lense-air interface). A large lense can also be stable

  • P. Martinez-Vazquez added an answer:
    What are the limitations of a Computational Fluid Dynamics (CFD) approach when used for engineering problems?
    CFD should not mistakenly taken as "Color Fluid Dynamics": Computational Fluid Dynamics (CFD) is being used extensively in almost all the engineering problems that can be solved by CFD. A number of commercial codes are very popular among many researchers. However, care must be taken about the limitations and applicability of such codes. Special attention should be given to the turbulence and other models used to solve a problem. Solutions to unknown problems should be dealt with engineering judgement and principles.
    P. Martinez-Vazquez · University of Birmingham
    Although this might beimplicity in the responses above, the use of experimental data is in many cases essential in order to validate the numerical model. The reason obviously being that the phisics of the phenomenon can be captured by well-controlled experiments.
  • Sylvanus Kupongoh Samaila asked a question:
    Can anyone show me how p-Laplacian and p(x)-Laplacian equations arise in electrorheological fluids, its origin and developments?

    If the domain U is not smooth with wrought boundary, can I stil use Lebesgue-Sobolov space with a variable exponent?

  • Naouel Daouas added an answer:
    How do I apply the Newton Raphson method to solve inverse heat conduction problem?
    I have the equations and boundary conditions.I have measured temperatures data at one end of the slab at x=L. I need to find heat flux at x=0. The problem is that I do not know how to start the iteration procedure and which values to use for starting conditions. Also what values should I assume. I have attached the implicit form of equation that I need to solve.Can someone explain to me this problem.
    Naouel Daouas · National Engineering School of Monastir

    If the surface heat flux is independent of time, the problem is a simple parameter estimation one. An initial guess of the constant heat flux is used to start the iterations and this value will be adjusted based on the measurements of temperature.

    However, if the surface heat flux is dependent of time, the problem is a function estimation one and needs appropriate methods like the Conjugate Gradient method with adjoint problem. Otherwise, you can assume the timewise variation of the surface heat flux as a piecewise constant function and handle the inverse problem as a parameter estimation one.

    You can see the details of the computational procedure for inverse heat conduction problems in : " INVERSE HEAT TRANSFER - FUNDAMENTALS AND APPLICATIONS, M. Necati 0zisik, Helcio R. B. Orlande, Taylor and Francis Eds, 2000.


  • Staffan Sjostrom added an answer:
    What are the best methods for droplet generation?
    What is the best method to produce uniform droplets in microchannels? Pneumatic pressure, syringe pumps? Is pressure control really better than syringe pumps? If yes, why? Please help me to understand better.
    Staffan Sjostrom · KTH Royal Institute of Technology

    I think both methods would work well to obtain reasonably monodisperse droplets. Syringe pumps may have the advantage that you have better control over your flow rate. Pressure controllers will give you faster response times so that "steady-state" is reached quicker, esspecially if you are operating in a high fluidic resistance system.

  • Mrinal K R added an answer:
    What is the importance of performance curve of pumps in industry?
    What are the applications of performance curve of pumps in industry which are doing in the lab test setup?
    Mrinal K R · Indian Institute of Technology Madras

    Thank you Giuma Fellah and Ahmad Hussain.

  • Tomas Mikoviny added an answer:
    Tight and durable connection between glass and teflon?
    I want to connect a teflon hose to a glass pipe (3 mm inner diameter, 5 mm outer diameter). The connection should be tight and durable. Inside, fluids will be transported (not pressurized, temperature range 5-40°C). * Do you have experience how to obtain such a connection, e.g. is there a special glue or clamp? * Where can I source flexible Teflon(tm) hoses for this purpose?
    Tomas Mikoviny · University of Oslo
    1) if you want to glue them together there is solution from Loctite - first using Loctite 770 primer + and use one of the 401, 431, 454 (for more see http://bit.ly/1iSSofh or contact the Loctite) 2) eventually would suggest following website to look at some fittings and tubing http://www.entegrisfluidhandling.com - one can get at least some overview on options 3) if you choose the method Faraz described I would recommend 1/4" OD tube with wall thickness of 0.030" - that would be quite easy to assemble with 5 mm OD glass tube and then you choose eventually any of the methods described above to fix even more
  • Despoina Pitsa added an answer:
    How to dimension a motor for a turbine?
    How can I or where can I find information about how to determine torque and rpm of a motor to produce a given maximal flow and maximal pressure with a centrifugal turbine? For e.g. this one: http://www.thingiverse.com/thing:13188 I guess the maximum pressure in case of a closed outlet is a function of the rpm, while achieving a certain flow with an open outlet would require a certain torque? An approximation would probably be enough. I did not find detailed information - and integration of the centrifugal forces is difficult enough yet already a pretty crude approximation. Literature about turbine design or possibilities to model one would also be interesting.
    Despoina Pitsa · Democritus University of Thrace
    I hope the following links will help you to: http://winds-energy.blogspot.de/2010/09/wind-turbine-is-rotary-device-that.html http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1099-1824(199804)1:1%2B%3C5::AID-WE1%3E3.0.CO;2-I/abstract http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1531394&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D1531394
  • Ahmed Hesham added an answer:
    What are sources of errors in dimensional PI -theorem of deflection relations?
    I was working on getting non dimensional pi-groups for a model and scaled down similitude of cantilevers. For a cantilever : I got a pi1 =Deflection "u"/length"l" So i used u/l )model = u/l )similitude I used simple example to prove this so a cantilever with 1 m length and 1mmx1mm square cross section of steel is used and deflection was calculated for 1 N at tip ! Scaled down Aluminium cantilever was used with 1/2 m length and 0.5x0.5 mm square cross section and I calculated its deflection under point load 1 N also at tip ! then I tried this relation : u/l model = u/l similitude assuming u of steel is unknown. But I did not get deflection for steel same as calculated! The error =8.7 %
    Ahmed Hesham · Ain Shams University
    I think I'm wrong in fixing the value of force !
  • Andreas Hantsch added an answer:
    How to model thermo-physical properties in two phase flow modeling?
    Consider parallel flow of two immiscible fluids within a channel with wavy interface between them (ripple). If it is desired to solve Momentum equation for this situation, the thermo-physical properties like viscosity how should it be modeled?
  • Arelo Tanoh added an answer:
    Does anyone know of an open source 1D finite volume shallow water solver for FORTRAN, that is openly available?
    I am currently having to integrate an actuator disc into a 1D shallow water code as part of my thesis. I have attempted this by putting a line discontinuity into a finite difference scheme, which simply does not work. Thanks.
    Arelo Tanoh · The University of Edinburgh
    Dear Chinedu, apologies for the overdue reply. The Matlab code for the 1-D SWEs would be very useful. Could you kindly send this to me ? Best regards
  • Rogerio Maestri added an answer:
    How can we estimate local velocity of expanded airflow?
    Air is being continuously pushed through a small long tube into a chamber (typically a rectangular prism or a cylinder) and then escapes through a similar tube out on the other end of the chamber. The tubes are about 3mm radius, the chamber may vary between about 0.5 and 150ml, and the flow speed inside the input tube can be as high as Re=2080, but is fixed for any given experiment. I'm trying to predict/estimate local velocities inside the chamber for various chamber sizes, input/output locations and flow rates. I'm unsure of what fundamental considerations are necessary.
    Rogerio Maestri · Universidade Federal do Rio Grande do Sul
    Dear Marta. . The Reynolds number at the entrance (2080) is a low value and it is near to the transition, then the prediction of the distribution of velocities is difficult. Moreover the numerical simulation becomes simpler. . You will have a jet that can be both turbulent and laminar entering a chamber that will tend to laminar flow. . A single velocity value inside the chambers is pretty pointless, because due to the characteristic flow it will have a very large variability. . I think your the case could do some physical simulations with the same or another fluid (eg water) maintaining the same Reynolds and introducing into the inlet duct dye, as is the low Reynolds can obtain a good result photographing the evolution of flow at the entrance of the dye, which is something simple without much hi Can you reliable results. .
  • Is there any previous research on the simulation of two phase flow in aero engines deaerator using ANSYS?
    I am looking for a previous research which investigate two phase flow of oil and air mixture in aero-engines deaerators.
  • Vitaly Domnenko added an answer:
    Which is the best book to learn Lattice Boltzmann Method for beginners?
    I'll have to later apply it to a problem of droplet flows, write computer codes etc.
  • Vipin Agrawal added an answer:
    Do I need to perform my microscale mixing analysis using turbulence or Laminar flow?
    I am doing analysis using FLUENT wherein two fluid streams mix together as follows. In a straight channel there is another inlet at the midway where the second stream of fluid enters (same fluid) and then both the streams pass through as one. My concern is whether the analysis can be performed using laminar assumption or do I need to consider any turbulence also? The channel cross section is of the order of 200 microns and the Re number at both the inlets is well within the laminar regime (around 200-500). P.S: The fluid is liquid under consideration.
    Vipin Agrawal · Indian Institute of Technology Guwahati
    I think there is one more problem in this . If your Re is around 200 - 500 (according to you) then it means it's a laminar flow and the mixing in laminar flow is quite unfeasible process. It would take (h^2/D) time for mixing where h - distance between fluids D - Diffusion coefficient Now if you do some practical calculation you'll get to know this value is around 10^9 second , that's something impractical because you would not wait that much for mixing to happen So what we should do is making flow turbulent and that can be done in a flexible micro-channel. More flexible the micro-channel is turbulence will happen at lower Reynolds number. So if mixing is happening you have to assume turbulence otherwise mixing wouldn't happen.
  • Daniel Irimia added an answer:
    Is there anyone who has taken a course in Microfluidics?
    If so what were the materials in the class? I mean any sources including books, notes and so on.
    Daniel Irimia · Harvard Medical School
    I highly recommend this book, that is an excellent overview of all the major microfluidic advances in the past 20 years. It is focused mainly on devices for biological applications, has awesome illustrations, and is a captivating read cover-to-cover: http://www.amazon.com/Introduction-BioMEMS-Albert-Folch/dp/1439818398
  • Muhammad Awais Khan asked a question:
    What is hydrodynamic cell separation? How does it work? Any useful link/Info?
    I am looking for a link or if any body of you can explain me about the hydrodynamic cell separation technique. I shall be very thankful to you.
  • Abdelaziz Bouchikhi added an answer:
    How can we determine the maximum time of the simulation of glow discharge based on the fluid model?
    The fluid model based on the three moments of Boltzmann's equation.
    Abdelaziz Bouchikhi · Taher Moulay University of Saida
    At the convergence of the magnitude of physic parameter
  • Chandan Pal added an answer:
    Can we utilise the relative wind energy of a moving train?
    While a high speed train is moving, the wind is blowing in the opposite direction. Can that wind energy be utilized to run the fans of the train? or if that wind can be utilized to generate power? like installing dynamo in the poles near the tracks
    Chandan Pal · Asansol Engineering College
    can we place dynamo in th poles near the tracks?
  • Mukkarum Hussain added an answer:
    Does anyone know where I might find a transient Aero-thermal test case?
    I need a transient aero-thermal test case for the validation of numerous procedures. I have one very good test case of x-15 but I need one or two more test cases. X-15 transient aero-thermal test case contains complete detail of free-stream conditions, material thickness, temperature measurement instruments locations, and skin temperatures. If anyone knows some other test cases which have these all data available for study please inform me.
    Mukkarum Hussain · NED University of Engineering and Technology, Karachi
    May you please provide me their link!
  • Mahmoud M. Abdelrahman added an answer:
    What is the best way to calculate airflow rate in a building interior whether using CFD or any other measurement tools?
    What is the best way to calculate airflow rate in a building interior whether using CFD or any other measurement tools?
    Mahmoud M. Abdelrahman · Kafr El-Sheikh University
    Thanks a lot prof. Hussain for answering my question. How can I empirically calculate the airflow rate using anemometer ?
  • Bernhard Semlitsch added an answer:
    How to analyse the influence of bulk viscosity of liquid flow in high pressure and in tiny hole?
    Bernhard Semlitsch · KTH Royal Institute of Technology
    As I understand it, the flow is pushed through a small hole. And in such a case the fluctuations are highly stretched in one direction and damped in the other two directions. Or in other terms the vorticity is stretched. I had a similar problem in a nozzle flow and I looked at the amount of stretching that the vorticity experiences when flowing through the constriction.
  • Abdallah Daddi Moussa Ider asked a question:
    Could anyone suggest some relevant papers on the use of the multifractal phenomenology for the Eulerian transverse velocity structure functions?
    I would appreciate if someone here could suggest some papers concerning the application of the MF formalism on the transverse Eulerian velocity structure function. I have found indeed several papers touching on the Eulerian longitudinal velocity structure function and also for the modulus and would like to know whether similar works have been also published for the transverse component.
  • Weidong Li added an answer:
    Why not directly solve PDE on cell interfaces to get accurate values and their evolution without depending on reconstruction?
    The most important technology in FVM is to reconstruct the variables at cell interfaces accurately. So why not directly solve PDE on cell interfaces to get accurate value and their evolution? Do you believe that it will be much accurate than the reconstruction method? We can directly solve PDE not only on the cell, but also on the cell interfaces. For example, in the UGKS presented by Xu and Huang and DUGKS presented by Guo et al., they solved the Boltzmann equation on cell interfaces.
    Weidong Li · Old Dominion University
    In fact, there is a type of Structure Preserved method which shares this idea. In the future, I believe that this idea will be accepted by more and more researchers. Specially, for the sigularity problems.

About Fluid Dynamics

Fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids (liquids and gases) in motion.

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