[Loekatoni]

Dear Foamers,


I have a question regarding the boundaries. I'm making a model of a horizontal microchannel with flow around a bubble. Now I'm starting with flow through the channel without the bubble inside to obtain the proper flowfield.


I have formulated the analytical solution, so I know what the flowprofile should look like and now I would like the induce pressure on the inlet and outlet which corresponds to my profile and check if OpenFOAM produces the same flowprofile.


The weird part about my model is that the bubble as well as the liquid are moving towards the right. But I take the bubble as the reference frame and to have that, the wall of the channel should move to the left with the bubble velocity. This brings in a complication, namely that the netto flowprofile for the fluid is partly positive (flowing to the right) and partly negative (flowing to the left).


I can't seem to figure out exactly how the pressure boundaries work in OpenFOAM and I have not succeeded in getting a physical logical flow. I can calculate the volumetric flowrate of the liquid and induce this on the right boundary, but the total Qv is negative, so it will flow towards the left. This is in conflict with the profile, which states that a part of the Qv should also exit on the right of the system.


Could someone inform me on how I should use the pressure boundaries and how I can define the velocity boundaries such that inflow and outflow through it is possible? My analytical pressuredrop goes from 1.11e5 to 1e5 or 128.324 to 115.607 if divided by rho.



Sincerely,
Loek


Edit: So what also is a possibility is that I fix my velocityprofile and check how the pressure develops over my system. If this corresponds it also validates the flowprofile. This was my first go to form for the boundaries and I tried to use codedfixedvalue for the inlet flow profile, but in my analytical profile I also have -U-TB (which is the bubble velocity, which needs to be substracted). If I put U_TB in the codedFixedValue boundary I obtain Co = 1.234e+123 or something. When I take it out it works, BUT no outflow is possible in this case, becausde the boundary states inflow happens, so I have eddy-formation near the inlet boundary.


Maybe someone has an idea via this path? The one where I declare the velocity(-profile) and validate via the pressure at steady state.