[assafwei]

Hi all,

First of all - I am new to CFD, so I am here to learn, please correct me if you notice any mistakes.
I am trying to validate fluent with a lab experiment, but I have a problem with the boundary conditions setup.
I'll try to explain my setup:
I have a small test chamber, in the inlet I can controll volume flow (measured in liters/min) and the outlet is atmospheric pressure (I am testing a valve that is fixed to the test chamber). I can also measure total pressure in a location near the valve. The results I get from the test equipment is volume flow, and pressure at a certain point in the chamber. When I start the test (and the analysis) the only thing I know is the inlet volume flow, so I am having problems determening the inlet BC, since I need velocity or mass flow rate at the inlet and my equipment (and customer requirements) is in volume flow, it looks as if I need to guess another variable in order to setup the analysis.

Any pointers on how to solve this?

Thanks.

[LuckyTran]

Do you already know your inlet density? Unless the problem is more complex, you can compute the inlet velocity needed to achieve your volumetric flow rate (mass flow rate divided by density and cross-sectional area). Same can be done if you want to specify mass flow rate.

[assafwei]

Hi,

I dont know my inlet density (no way to measure it, and density is changed from one valve geometry to the other).

[CFD-fellow]

Hi why dont you know the inlet density? what is your test working fluid?
Regards

[assafwei]

Hi,

I know the fluid theoretical density (air) but there might be some compression of the air ocurring at the inlet (the inlet is fed from a 6 bar compressor going through some valves and some tubing hence I dont know the exact pressure at the inlet).