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August 8, 2001, 12:09 
SIMPLE

#1 
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I am tring to solve for a cavity driven flow using the well known SIMPLE algorithm. As I increase the Reynolds number by an order of magnitude of 10 my velocity at the node just below the top node and at extreme right takes a value higher than the top velocity or the shearing velocity. Is something wrong with my solver or my discretised equations.


August 8, 2001, 19:26 
Re: SIMPLE

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(1). As the Reynolds number is increased, the boundary layer will be confined to the wall region, and the velocity gradient will increase accordingly. (2). In other words, the mesh has to be redistributed to get a better resolution. (3). What is the actual Reynolds number you are calculating? and What is the mesh size? and distribution?


August 8, 2001, 23:06 
Re: SIMPLE

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1)assign deltat thru stability criteria (CFL, grid Fourier). 2)solve P' eqn well. 3)incorporate cross sweeps (x and y directions) for momentum and P' eqns.


August 9, 2001, 08:18 
Re: SIMPLE

#4 
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Are you using any upwing? If not, it could be the caused of your problems.


August 9, 2001, 09:42 
Re: SIMPLE

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I am solving for a steady state solution and so not discretising in time. Solving for P correction equation right now I calculate the value of a_e as calculated in the momentum equations and not just the sum of convective and diffusive face at that face. I am looking at a Reynolds number of 4000. And I am using a staggered grid. I am solving for a box of 10cm*10cm*10cm and a 30*30*30 grid size. The problem is that when i solve for guessed velocity for higher Reynolds number my guessed velocity at the one of the nodes becomes higher than the shearing velcoity. Any suggestions as to what I should read for trteating the singularity at the right hand corner. Also should I be needing ghost cells if I use a staggered grid. Thanks


August 9, 2001, 09:43 
Re: SIMPLE

#6 
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If you mean upwind scheme for the interpolation of convetive terms, Yes.


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