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Inlet/initial velocity for fractional step

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Old   March 31, 2006, 03:41
Default Inlet/initial velocity for fractional step
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zonexo
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hi,

may i know how does one specify the inlet velocity for the flow past cylinder for FVM unsteady fractional step scheme on non-staggered cartesian grid? rhie-chow interpolation has been used.

e.g. u=1 at inlet.

For the extreme left column of cells, I tried to specify u=1,v=0 at cell center. face velocity (perpendicular to cell face) =1 for east & -1 for west.

The answers i get for time steps less than around 100+ is one whereby:

1st column (extreme left) u~1.05 2nd column u~0.95-0.98 3rd column u~>1.05

It increases and decreases until nearing the cylinder and it starts to decrease uniformly.

after more time steps, the fluctuation decreases and away from the cylinder upstream u~1.

however, i feel that this initial condition doesn't seem right for an unsteady case. i've also tried to start from u=0.01 and slowly increasing it to u=1 but the fluctuation still happens.

Can someone enlighten me on what is the correct initial condition to be applied? Has it got to do with the term "solenoidal"?

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