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 Johnny Lam May 27, 2001 13:52

Someone helps me!

I'm a student. In the beginning of solving cfd problem, I met some troubles: Although I studied aerodynamics, FEM, but writting myself a code to solve "flow over a cylinder" (in ANSYS-flotran), I saw that my results weren't exact as experimental. I think that I need some simple codes for reference. They must simple,easy for a student who has just known Flotran-Ansys. Someone can let me know where can i get some codes? Thank you very much.

PS: I sent also my code for problem "flow over a cylinder", please tell me what is is wrong,how can i rewrite...?

!Re = 3.09e-6 (To compare with Cd in the book:FUNDAMENTAL OF AERODYNAMICS. JOHN ANDERSON) !air density = 1.23 !Velocity = 45 !Diameter = 1 !Vicousity coeifficient = 1.789e-5 !rectangle size is 150x100

/unit,si /prep7 rectng,0,150,0,100 local,11,0,75,50,0,,,,1,1 csys,11 wpcsys,-1 pcirc,0.5,0,0,360 csdele,11,,1 aovlap,all adel,2 csys,0 wpcsys,-1 lsel,s,,,1,3,2 lesize,all,3,,,1 lsel,s,,,2,4,2 lesize,all,2,,,1 lsel,s,,,5,8 lesize,all,,,64,,1 allsel et,1,141 amesh,all

dl,4,,vx,45,0 !Velocity at inlet line = 45 dl,4,,vy,0,0 dl,2,,pres,0,0 !Pressure at outlet = 0 dl,1,,vx,0,1 !Boundary is in condition of a windtunel dl,1,,vy,0,1 dl,3,,vx,0,1 dl,3,,vy,0,1

dl,5,,vx,0,1 !lines on circle, Vx=Vy=0, end line selected dl,5,,vy,0,1 dl,6,,vx,0,1 dl,6,,vy,0,1 dl,7,,vx,0,1 dl,7,,vy,0,1 dl,8,,vx,0,1 dl,8,,vy,0,1

/solu FLDATA5,OUTP,PCOE,1 !add a pressure coefficient DOF fldata1,solu,turb,1 flda,iter,exec,500

flda,prot,visc,constant !fluid property, constant flda,prot,dens,constant fldata,nomi,dens,1.23 fldata,nomi,visc,1.789e-5 allsel solve

 John C. Chien May 27, 2001 20:46

Re: Someone helps me!

(1). I could not understand your message. (2). The flow over a cylinder has been studied for many years, so there should be plenty of information available out there on the subject. (3). My suggestion is: write down the governing eqautions. If you are interested in 2-D, laminar flow, then convert the equations into vorticity-stream function formulation. Then you should be able to solve this set of equations by reading some CFD books, or related published papers. (4). It is a fairly standard test case. The important thing to remember is that, you must define your problem in terms of the Reynolds number, which will determine the characteristics of the solution. (Don't try to push it into turbulent flow regime at this point of study.) (5). It is also a good idea to have a good CFD teacher, so that you can follow his foot steps. CFD is not a DIY project yet.

 Johnny Lam May 27, 2001 23:56

Re: Someone helps me!

I wrote a code in ANSYS-FLOTRAN to solve "flow over a circular cylinder" but solution was very diffrent with experience. So I need some codes for reference. In my country, no one know well about ANSYS-FLOTRAN, so I cannot ask someone (my teacher said also). Could you give me the codes for this problem or the address for download them? Excuse-me for my poor English.

 Peter Attar May 28, 2001 08:51

Re: Someone helps me!

ANSYS has a group on www.egroups.com...go to this site and sign up for the group,check the archives first for messages on this topic. If you don't see any posts on this subject post a message to the group with your name and school and a detailed explanation of your problem and someone is sure to be able to help you.

 S.P.Asok May 29, 2001 05:12

Re: Someone helps me!

May I know what is a DIY project.

 John C. Chien May 29, 2001 05:47

Re: Someone helps me!

(1). DIY="Do It Yourself"=All you need to know is how to use a screw driver and a hammer.(2). (!DIY)=Need to receive professional training first.

 S.P.Asok May 29, 2001 07:07

Re: Someone helps me!

I do totally agree that CFD is not a DIY/LIY(Learn It Yourself)affair.I have been thinking that it was my view, but it seems many share the same view.

 rupa dutta June 1, 2001 06:54

Re: Someone helps me!

John

I connot agree more with you.

Many (most) of us buy fluid flow s/w package as a DIY kit and 'play' with it. Well, if you can set up a menu ( geometry, grid etc.), it'll give you a colourful flow 'picture'.

Thanks. I learnt witty term.

rupa

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