Three components system
 

We are two mechanical engineering students, we have to develop a student project about a combustor using Ansys CFX, so we're quite new to this kind of works. In our problem there are two noozles, one of those containing air and the other containing CH4; the jets coming from those noozles are mixed together downstream the pipe. We have three domains, one for air, one for CH4 and one for the mixture of them. We settled the outlet pressure condition at 0 relative bar, the inlet condition is the mass flow rate of air and CH4 (fixed), and we put a fluid-fluid interface corresponding the outlet of the noozles and the inlet of the downstream pipe. When simulation starts, it stops quickly, before starting iterations; and in the scripting line Ansys write that in the air and the CH4 domains pressure is not defined. The same simulation working only with air works correctly. How can we solve this problem?

Thanks for the help

Alessandro and Cristiano