Hi, there. If somebody has some ideas that under what conditions the boundary layer should be used in duct flow, using a CFD software?

Can you explain your question better, are you asking if there is a boundary layer in flow through a duct? The answer is yes, the boundary layers from all surfaces meet in the centre of the duct. Or are you asking whether you should use a boundary layer code for this flow, or something else?

Dear sir, I am student in polymerization enginnering that want to know the basic concepts of cfd. please send me brief introduction to me to know more about this subject. your sincerlly

nima khadem mohtaram

tehran polytechnic

Read "CFD - An Introduction to the Finite Volume Method" by Versteeg & Malalasekera, Longman Publisher. Very good, very brief (200 pp.).

Hi, Andy, sorry for late reply. I am simulating a kind of pipe flow, using a commerical CFD software. And I want to know when I simulate flow states, if I should put boundary layer near the pipe wall region.

Thank you.

Yes, you need to resolve the boundary layer correctly at least at some level. The standard way of doing this is to compute a parameter called y+, which is a non-dimensional kind of wall Reynolds number. This will allow you with the use of some other simple relations to get a rough estimate of where your first grid point should be. Note that making this judgment requires that you have knowledge of the turbulence model you are using and the method you are using to extrapolating this to the wall. Different wall models and turbulence model, will have a different requirement on the y+, again note, that this will increase the mesh requirement depending on how small the value of y+ is.

Hope this helps, will mean nothing to you if you have not heard these terms before, but if you explore some literature on the net, hopefully it will become clear what I mean

Cheers

Andy

You give me much help!

Hi

My vision is basically divide into four steps for CFD. 1st Step Problem specification and Geomerty preperation

2nd Step Set of Governing equations and Boundary conditions

3rd Step Numerical Grid Strategy and Discretization

4th Step Solve the system of Linear equations

I think you can get the basic idea for CFD by studing the above steps individually.

Thank you

Ranga