# boundary condition and hydrostatic pressure

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 November 24, 2003, 12:39 boundary condition and hydrostatic pressure #1 Atit Koonsrisuk Guest   Posts: n/a I conclude after reading some topics in this forum that when I model flow with buoyancy effect, I have to include the hydrostatic pressure with the boundary conditions. Is my understanding right? I model the flow in a equipment with high chimney. This equipment allow the working fluid to flow in through the inlet portion and flow out through a chimney. The flow arise due to natural convection within the equipment. Do I have to add the hydrostatic pressure to the 'inlet' and 'outlet' boundary conditions. Actually I already tried to add it, but I got the divergent solution. Thank you very much. Atit

 November 24, 2003, 12:49 Re: boundary condition and hydrostatic pressure #2 Atit Koonsrisuk Guest   Posts: n/a Since the density will be changed with temperature, then I enter the expression for density as the function of temperature in the fluid property form when I define the model. Then I followed the suggestion in one topic that specify 'density*g*y' as the expression for pressure in the boundary condition form. I got the error message say that 'density' is not available for this expression. Could anyone please suggest me how to fix this problem? Thank you very much.

 November 25, 2003, 20:39 Re: boundary condition and hydrostatic pressure #3 zjmjm Guest   Posts: n/a I suggest you read the handbook of CFX, you can get the method that solve your problem in tutorial 3.

 December 7, 2003, 05:46 Re: boundary condition and hydrostatic pressure #4 Amit Katiyar Guest   Posts: n/a hello Atit, i also have the same problem as you have in your chimney problem. I suspect that the static pressure taken by cfx-5 is . so we should define this value only as proper boundary condition. but i didn't get proper results. I am also unanswered about this question. share your views with me. amit