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kim October 25, 2000 04:40

gravity
 
I have problems with including gravity force to my model(material is water).The stratification of hydrostatic pressure has developed but the values of static pressure are totally false.They are about four orders of magnitude less. Did you have same problem? Can you help me ?

Trac October 26, 2000 02:21

Re: gravity
 
Fluent reports gauge pressure, this probably accounts for your difference. See page 7-57 of the manual for more details.

Maurizio Barbato October 26, 2000 06:08

Re: gravity
 
Hi,

may be Tracie is right.Then to have the "real" value of the static pressure you can use the Custom Field Function panel and define the static pressure as:

p_new = pressure + p_op

where "pressure" is the one calculated by fluent (i.e. the gauge pressure) and "p_op" is the Operating Pressure value set up in the Operating Condition Panel. In this way you can plot the static pressure in each point of your field.

Try this and let us know.

Cheers

Maurizio

Volker Pawlik October 30, 2000 08:28

Re: gravity
 
Hi Kim,

as far as I remember, Fluent does not report the so called hydrostatic head (rho*hg*h) when you display static pressure distribution. Hence I am surprised that you get a stratification out of your results yet?!

I assume that you are not using the Boussinesq Model. To get a stratification set your reference density to 0. Probably your pressure values will change and give you the hydrostatic differences you are looking for.

For more information concerning Fluent's handling of hydrstatic pressure contact Peter Wilde, UK. He helped me that time I was concerned with hydrostatic boundary layers.

P.S. I think the Users's Guide description of hydrostatic head handling inside the momentum equation is indeed very bad to understand...


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