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 katakgoreng December 27, 2009 09:24

Problem with SIMPLE algorithm

2 Attachment(s)
I have written finite difference SIMPLE algorithm to solve the Navier Stokes equation in Matlab. My problem is that I don't know how to specify boundary condition for Poisseuille flow. If i specify inlet velocity, the solution tend to blowup. I suspect that somehow I don't specify the pressure boundary correctly.(In the matlab code if I specify the pressure boundary for inlet and outlet but no velocity boundary at the inlet, the solution does not blow up but the problem is that I cannot control the inlet velocity) I managed to solve Couette flow and Driven cavity problem with no problem though..Care to advice me on what I have to do. I attached also the code for the SIMPLE algorithm that I write..

 jyothishkumar December 27, 2009 11:13

boundary condition

You are solving flow in a duct basically. Use velocity inlet and pressure outlet bc. Which grid r u using ? colocated or staggered

 katakgoreng December 27, 2009 11:21

Quote:
 Originally Posted by jyothishkumar (Post 240988) You are solving flow in a duct basically. Use velocity inlet and pressure outlet bc. Which grid r u using ? colocated or staggered
I'm using staggered grid..if i set the inlet velocity to v=1 and pressure outlet p=0, how about inlet pressure, do i need to extrapolate it with inner pressure?

 jyothishkumar December 28, 2009 00:02

yes exactly. p(1).value = p(2).value where p is the pressure and numbers indicate the node location

 katakgoreng December 28, 2009 05:09

Quote:
 Originally Posted by jyothishkumar (Post 241004) yes exactly. p(1).value = p(2).value where p is the pressure and numbers indicate the node location
hmmm..it's that simple? i'll try it..
for anyone who has run my code, do comment on what I have done..thanks in advance.. :D

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