Lower Pressure than outlet
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Hi,
I am currently running a simulation on the flow in porous media. Right know I face quite strange effects when post processing my simulation. I have boundary condition of inlet: 5g/s a Fluid outlet: static pressure : 101300Pa Multiphase flow: begining: everything filled with Air, then Fluid gets filled inside cavity Transient Simulation. When I run the simulation for too long i get the error: A wall has been placed at the following Domain Outlet to prevent flow inside... If I run the simulation a bit shorter, so I stop before the error occurs, the pressure at the outlet is lower than the boundary pressure namely 83000Pa. How is this possible? Any ideas how to prevent this? I attach a picture of the solution a few timesteps before the error comes up. Thank you for your help. |
First of all, you should be using 0 Pa at your outlet, and a reference pressure of 83000Pa. You are getting recirculation, extend your outlet further away from your hump, perhaps 20*h. When you stop it early the model is not converged and you are getting rubbish.
600 psi is a heck of a lot of pressure drop though.... |
Thank you for the advice.
I am running a transient simulation. The main purpose is to detect the flow front, and the pressure in the cavity during the injection. When I inject the Fluid at the inlet the Air which is in the cavity at the beginning is supposed to be pushed out of the cavity with pressure (outlet pressure =0 ) When running the simulation now I get negative values for pressure which in my opinion is physically impossible for am mass conservation point of view. As the cavity just has a specific length I think I would change the results if i make it longer. Tell me if i´m getting something wrong. |
Do you mean negative absolute pressure or negative pressure? Negative absolute pressure is a worry in most cases (but note in some extreme cases negative absolute pressure is possible and really does happen) but negative pressure is normal - it just means the pressure is less than your reference pressure.
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