radiation modell with two different fluids
 

i tried to create a simulation in a pipe with two inlets where two different fluids are streaming in. Because one of them is a mixture of air and steam and i have very high temperatures i want to use a radiation modell. but as soon as i have chosen two different materials in my domain i can´t select any radiation modell. because of the 2 inlets i can´t define a mixture and i also want to see the different streamlines and velocities of the different fluids... is there a way to have a radiation modell an different fluids?

thanks

any help?
 

doesn´t anybody know how to solve the problem?