Learning Forum

[Chinmaya Kumar Patra]

I am trying to do a two-phase boiling simulation in fluent in a rectangular channel. I have given constant mass flux inlet as inlet BC and gauge zero pressure as the outlet BC. But during the transient simulation run, I found my outlet pressure varies with time, but it should be constant as i have given in the BC

[DrAmine]

If you are providing a Dirichlet BC for the pressure at the opening that should and will be respected. Can you add screenshots showin that the gauge pressure is variying along the outlet (turn off node values) along with the BC settings screenshot.

[Chinmaya Kumar Patra]

Thanks for the input; the simulation run time is 9 ms. Kindly find the screenshot for set BC and the variation of P_inlet and P_outlet with time. The P_inlet and P_outlet I have calculated by taking the area-weighted average of pressure at the inlet and outlet named section of the computational domain.

[DrAmine]

How are you post-processing "P_outlet"?

[Chinmaya Kumar Patra]

I am not post-processing the P_outlet. During the problem setup, I created a report definition for which I created two parameters, P_inlet and P_outlet, calculated by taking the area-weighted average of pressure at the inlet and outlet named section. During the transient simulation, I am writing the P_inlet and P_outlet data at each time step, using the report data I have plotted the transient P_inlet and P_outlet as shown in the screenshot.

[NickFL]

What happens if you switch to a massFlowAve(Pressure) at the outlet instead of an areaAve(P)? With the two phases I could potentially see a difference of a couple thousand Pa between the two averaging methods.

 

[DrAmine]

Static Pressure at the Outlet should be fixed to that zero gauge pressure (as we have anyhow subsonic flow here). Can you please add some more information about the way you created the report definition: add a screenshot please.

[Chinmaya Kumar Patra]

 

This is how i created the report definition for outlet pressure in the setup of Ansys fluent

 

[Chinmaya Kumar Patra]

Similarly i have created the report defination for p_inlet and for pressure drop i have used expression. The screenshot for p_outlet is given earlier and for rest is given below