can we mix two different fluid in flow simulation?
Yes, you can do fluid mixing problems in SOLIDWORKS Flow Simulation for up to 10 fluids in a single analysis. Here is a video showing a setup of such a problem (GoEngineer - Flow Simulation: Fluid Mixing). Also, recently in the release of SOLIDWORKS 2018 you can do multi-phase (aka free surface) Flow analysis that looks something like this (GoEngineer - Flow Simulation: Free Surface).
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