High negative pressure in incompressible flow simulation
 

Hi,

Good afternoon!

I have been running an unsteady incompressible flow case with SRF using a solver which is a modified version of pimpleFOAM (no changes to pEqn and UrelEqn) in OF v18.06. I used fixedValue pressure BC at inlet and outlet which are set to 0 (i.e. gauge pressure assuming 1.013 bar atm pressure).

I have been experiencing high negative pressures. I understand that in incompressible flow what matters is the grad of pressure and not the pressure value itself and the pressure reported by OF is kinematic pressure.

When I convert -700m2/s2 to absolute pressure (-700m2/s2*850kg/m3 (fluid density)+101325Pa (reference pressure))= -493675 Pa = -4.9bar. The absolute pressure comes to be negative, which should not be the case.

The velocity values (absolute and relative) seems to be reasonable.

Can anyone help me understand how to treat the pressure and what I may be doing wrong while calculating absolute pressure?

I have read all possible forums with respect to pressure in incompressible flow but I am out of ideas to see how to avoid negative pressure value.

Thank you in advance.

Best,
Hiral