Using proper boundary condition for mass flow
 

Hi all,


I am trying to implement inletOutlet BC for the inlet because I want to avoid the back flow but at the same time I want to input the constant mass flow rate instead of inlet velocity. I should mention that I cannot implement flowRateInletVelocity due to reverse flow. How can I deal with that?


Best regards,
Masih

It seems that it may be more appropriate to specify a total pressure on the boundary if the flow direction may change in/out of the domain. The total pressure could then be adjusted until the requisite mass flow rate is obtained through the boundary.

Thanks for your fast reply. In this case, the inlet pressure is read from a csv file. Besides, the upstream pressure is too high which makes considerable pressure gradient. so I think totalPressure is not proper for this simulation but thanks anyway.

I assume that since your statement included "inletOutlet" that you are using OpenFOAM. The "fixedMean" bc (ref. OF v. 7) may work for you to get the requisite mass flow when the bc exhibits both inflow and outflow. However, I must preface that I have not used this bc myself before.

What does this mean? Backflow on an inlet? Backflow at an inlet is inflow or outflow?

If you use fixedValue or flowRateInletVelocity, you won't get unwanted outflow on your inlet. flowRateInletVelocity is based on fixedValue, but adjusts the value until the massflow/massflux matches the setting. I don't follow why you can't use these?

The inletOutlet BC is a zeroGradient BC that switches to fixedValue whenever there is backflow/inflow but only if there is inflow. If there's no inflow, it's effectively a zeroGradient condition.


So what are you trying to do exactly? You want to impose a mass-flow the inlet. But how is that different than imposing mass flow at the inlet?