Transient analysis of laminar subsonic flow of two gases with high density difference
I am trying to simulate the flow mentioned in the title. It is a 2D analysis. I am using 2019 Student version of the ANSYS. I am using pressure based solver as it is low Mach number flow. There is no temperature difference between two gases. One of the gas is stationary(or ambient) and other one is flowing and mixing with the stationary one. Due to high density difference I have included the effect of gravity. I have four major doubts regarding the simulation, which are as follows
1. Should I turn on the Energy equation?
2. Which of the solver from SIMPLE, SIMPLEC, PISO and COUPLED will be more suitable to this particular problem?
3. As one of the gas is considered stationary, all the outlet are pressure_outlets. I am having problem in understanding the settings of Backflow condition. I have read the manual but couldn't understand it much. For the backflow should I specify static pressure or stagnation pressure?
4. In the real situation both the gases can come out or go into the mesh domain. ANSYS gives option to specify mole/mass fraction of both the gases. How to specify backflow species for this situation?
I have crammed all the four questions into this one post because I thought those are inter related. Sorry if you find this post too long.
Thanks in advance for any kind of help.