# Outlet with mass flow specified: temperatures diverge

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 April 25, 2016, 08:57 Outlet with mass flow specified: temperatures diverge #1 New Member   Sarah Leenknegt Join Date: Aug 2015 Posts: 13 Rep Power: 4 Dear, I am trying to run a case with an air curtain at the entrance of a large building, including an outdoor "box" with athmospheric boundaries. I keep seeing the temperatures at the outlet boundary diverge to unrealistic high values. The meshcheck is successfull, and further refinements have also been made, so I assume the problem is my boundary condition at the outlet. The high temperatures occur at the boundary cells at the outlet area. Already after 20 iterations, the problem starts. I can post pictures of the geometry with mesh, when required. The case is running with buoyantboussinesqsimplefoam and kwSST, GAMG solver for p_rgh. My outlet BDC: - p = fixedfluxpressure - p_rgh = fixedfluxpressure - T = 12 °C (in case of backflow) - v = x 0; y 1.8; z 0 m/s - omega = zero gradient - k = zero gradient - kappa, alpha, nu = calculated Important is that I can define the mass flow at the outlet, otherwise the supplied hot air from the air curtain would just flow through the door to outside. I would appreciate any feedback on potential errors! I have been playing around with different BDC's, but have not found a solution. Or should I look again at my mesh or something else going on with the solver? In case relevant: My inlet BDC: - p = fixedfluxpressure - p_rgh = fixedfluxpressure - T = 32 °C - v = x 0; y 0; z -6 m/s - omega = turb mix length 0.1 m - k = turb intensity 5 % - kappa, alpha, nu = calculated My athmospheric BDC: - p = fixedfluxpressure - p_rgh = totalpressure - T = -4 °C - v = pressureinletoutletvelocity - omega = turb mix length 0.1 m - k = turb intensity 5 % - kappa, alpha, nu = calculated Thanks a lot! Sarah

 May 10, 2016, 05:38 #2 New Member   Sarah Leenknegt Join Date: Aug 2015 Posts: 13 Rep Power: 4 In case it can help someone else: The solution was to set the thermal boundary condition at the outlet to zero gradient.

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