The fluids are runing through a horizontal pipe under high pressure and high temperature, for example, 20atm. How to specify "Reference Pressure" in Domain Options and how to specify "Static Pressure" on the Outlet boundary? Thank very very much for your answers.

Best regards, David

Dear David, If you are using TASCflow you can give "opening" instead of "outlet" to give static pressure at outlet. Otherwise by continuity equation calculate velocity at out and give total pressure BC at outlet.

regards,

sheetal

Specify your Reference Pressure as 20 [atm] and your static pressure at the outlet to the desired static pressure minus the reference pressure.

Robin

Thanks Robin. But how can I know the desired static pressure? If the horizontal pipe is very long with a quite narrow diameter, can the desired static pressure be zero? (because Pstatic=density*g*h, since h is near zero).

Regards David

David,

You have your equations mixed up. Pstatic = density*g*h is used to calculate hydrostatic pressure. If you're pipe were standing straight up and the fluid was not moving, that is the pressure distribution you would see. You may want to bone up on your fluid mechanics before continuing.

One end of your pipe must be open to atmosphere or some sort of resevoir. Use the sensible pressure for that boundary. In the end, since your flow is most likely incompressible, it doesn't really matter what you set your reference pressure to. If you specify a static pressure at your outlet equal to zero (relative), the remaining pressures will be reported relative to that outlet. That should suffice.

Regards, Robin