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pi May 25, 2004 11:56

hydrostatic and static pressure
Hello, Im simulating a two phase flow. Imagine a bucket with water. The reference pressure is set to zero. As initial condition I set the hydrostatic pressure as the relative static pressure being zero in the interphase and increasing with depth up to 3e6 Pa. When I visualize the initial condition pressure field in Post(static pressure I assume) it is ok and in agreement with the above variation but in the next timestep the pressure field is almost uniform and about 4e6 Pa which makes not much sense. I guess that hydrostatic pressure term is not included, but it was in the initial state? May anyone make me clear how the pressure is dealt by Post?

thanks pi

test May 26, 2004 00:14

Re: hydrostatic and static pressure

I am not sure which version of software u r using... CFX-5.6/5.7. In case you are using CFX-5.6, the pressure would not include hydrostatic head. there are two work arounds for this problem.

1. For the results create another variable in POst which is Static pressure+hydrostatic head. (since ref press=0)

2.Set the buoyancy reference density=0 in pre. This will include the hydrostatic head in the pressure equation.

Anne May 26, 2004 09:53

Re: hydrostatic and static pressure
Hi Test,

Take CFX5.6, why do you reccommend that the bouyancy reference density in Pre be set to zero? Typically, the buoyancy reference density in a two phase system is taken as the density of the continuous phase (at least for the inhomogeneous approach). If you take it as zero, what is the implication of this on drag and body forces that have effect on the over all flow field, pressure, etc?

regards Anne

test May 26, 2004 10:35

Re: hydrostatic and static pressure
HI, Well this is due to some limitation in the code. I cannot provide you the explanation which I have in a powerpoint presentation to explain this fact. You can contact your local CFX support who should be able to help you out.

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