Heat flux boundary condition
 

Hi, i am trying to simulate flow boiling in a channel with a fin array inside. the heat comes from bottom of the channel. i have done one 3D simulation, but it took very long simulation times, so i try to do 2D simulation instead. the domain that i choose is the cross sectional area of the channel, so the fin array can be captured, but the problem is i couldn't put the heatflux boundary condition in my model because the heated base wall is not captured in the model. the current model is cross sectional fin array surrounded by the fluid flow. Does anyone know how I can set up heat flux as a boundary condition in my model? thank you