I’d like to set up a boundary condition similar to a velocity inlet, but with a pressure-dependent velocity: velocity = resistance * (pressure - input pressure). Resistance and input pressure are constants for the simulation.
This is similar to the behavior of a constant pressure source connected to a filter that has flow roughly proportional to pressure drop. My use case is to simulate a HEPA filter, velocity is roughly 148 ft/min when the pressure difference is 0.1 inH2O and changes linearly with pressure, so in standard units resistance is 0.03 m/(s*Pa). The filter is big, and velocity definitely varies across the surface, so I can’t model it well as a regular velocity inlet.
How can I do this?
I assume some kind of custom boundary, I looked in that section but couldn’t figure it out.
Hi there @aizvorski!
If you work with a pressure drop and know about these, you could theoretically make use of the porous media option. Have a look at the doc here: Linear Coefficient & Power Coefficient for Power Law Porous Media
Best,
Jousef
Hello Jousef - This seems perfect for what I’m working on, I’ll try it right now. Thank you!
I think I’ll need to add a thin plate of porous media at the inlet. For “Power law medium”, could you please let me know what the units are for Linear coefficient and Exponent coefficient? Does the formula assume Pa, kg/m, m and m/s?
At first glance, the coefficients do not seem to have units. Feel free to check out this spreadshit and make a copy for yourself: Readyuse-Perforated Plate.xlsx - Google Sheets
Let us know if you have any further questions.
Jousef
