Learning Forum

[Mohamed Ramon]

[CFD_Friend]

Hi Mohammed,

Can you give a decription to your problem. For some reason I can only see the title (Fluid Flow).

Thanks

[Mohamed Ramon]

its a simple internal flow inside a pipe. Air flow inside a 0.1 m diamete pipe with about 5 m/s velocity.

 

[Rob]

Have you done the courses in the Learning section on here? 

[Mohamed Ramon]

you can give me the link. On the other side, I finished some other courses and working with fluent several years ago and still have the same question. Why i have to set the flow as turbulan or laminar. For example if i have a 0.1 m pipe with internal air flow with 5 m/s velocity, this case according to reynolds numper should me a turbulant flow therefore, asnys should work as that withot asking me. But if i set it as laminar flow, will force the flow to be laminar other than reality !!

[Rob]

/courses/index.php/fluids/

Look at the turbulence question in another way. Why wouldn't you set a turbulence model given you need to decide what you need in your model. 

[Mohamed Ramon]

I got it but in this case which it's a turbulant flow in real, if i simulate it as laminar flow, how can i accept the laminar result. Would it be false in this case or illogical?

[Rob]

There's a theory that if the mesh is fine enough, and the time step small enough that a laminar flow will pick up the turbulent eddies as part of the result. Given the mesh cell count would be near infinity and the run duration would be rather long I'm not sure we'll ever find out. 

Being slightly more realistic, the result would probably not converge well, and may not be overly accurate. Try running laminar and then turbulent and compare the results.