Good evening. I am a student, doing a project regarding CFD simulations for a Stirling engine. I would like to ask how would one set the boundary conditions such that I could simulate a cycle involving the expansion of the working fluid and the pressure changes that would bring about the movement of the displacer (or piston).

Initially I had tried to simplify the problem by having adiabatic walls, and then setting a single real wall at the hot reservoir with a high temperature. When I run the simulations, however, there was barely any results apart from the immediate vicinity of the wall.

I had tried scouring the internet for possible solutions, but have ultimately hit a dead end. Would someone point out my mistakes and advise me on how I could fix it, please?

The following is some screenshots of my cut plots

http://puu.sh/nZnIY/6ab133b4ef.jpg
http://puu.sh/nZnIY/6ab133b4ef.jpg

http://puu.sh/nZnM2/02d0540657.jpg