[williamchina]

I am simulating a sampling valve in the engine cylinder wall. The sampling valve is connected with a vacuumed sampling tank. At a certain range of crank angles, the valve will open and the reactive gas expansions into the sampling tank.

When the sampling valve is closed, it behaviors like a wall with the same temperature as the cylinder wall. When the sampling valve is open, it behaviors like an outflow boundary, with a certain mass flow rate.

Can I set the valve as a outflow condition with mass flow rate equals to zero when the valve is closed? If so, what's the temperature boundary conditions for it, especially when mass flow rate equals to zero. What's the difference comparing to the wall boundary condition, where a Dirichlet temperature condition can be applied.

Thanks,
Weiqi

[xieshengbai]

Dear Weiqi,

It is hard to say whether or not you can implement boundary conditions (BC) on valves, since we don't have your geometry. Normally we don't do that. Instead, the outflow or inflow BC should be applied on the exhaust or intake port. Maybe you can add those ports containing the valves into your model.

For the temperature BC on the valves, if your grid resolution is sufficient (say, for low Reynolds number flow), then you can use Dirichlet BC. Otherwise, the law of the wall (LOTW) is recommended. Note, you have to specify the wall temperature even for the LOTW, which is used to calculate the temperature gradient only.

Best regards,

Shengbai

[williamchina]

Thanks a lot!