Boundary Conditions not being maintained (Solved)

[Me-Goosa]

Hello and thank you in advance,

I'm trying to learn PeleC and AMReX and running into the issue where my boundary conditions are being initialized, but aren't being maintained as constant. I want a flow to be coming in from the inlet constantly.

What I'm setting is that I have an initial boundary condition setting the inflow to ~500kPa, 3300 K, and ~1150 m/s and I'm setting the ambient conditions to ~100kPa, 300K, 0 m/s. What I'm getting is the flow coming out at ~300kPa, like it's been averaged between the two.

Is there a specific thing you have to do for the inlet to remain constant throughout the entire simulation?

[dmontgomeryNREL]

Welcome to the PeleC community! In general, if you're prescribing an inlet velocity you shouldn't also fix the pressure at the inlet. Doing both can lead to over-constrained or conflicting boundary conditions. For example, the EB-FlowPastCylinder test case prescribes a constant inflow velocity and temperature, while allowing pressure to adjust based on the solution.

For your case where the inlet temperature is much higher than the initial state, I would recommend slowly ramping up the temperature at the inlet from the initial temperature. Something like this in your bcnormal function:

// Ghost state for temperature
T = prob_parm.T_in;
// Ramp up the temp over t_ramp_T seconds
if(prob_parm.t_ramp_T > 1e-12){
  T = std::min(
    prob_parm.T_in,
    prob_parm.T_0 + (prob_parm.T_in - prob_parm.T_0) / prob_parm.t_ramp_T * time);
}

where t_ramp_T is the time in seconds it takes to go from T_0 to the inlet temperature T_in.

[Me-Goosa]

Thank you for your response, it helped me get it working! I was over constraining it.