[Walther]

Hello,

I´m a student and pretty new to cfd/star ccm+. I want to get the moment/torque that is produced by the air in the cylinder of a combustion engine at specific distance to the cylinder head.

The simulation is steady state and I have one region that consists of the surrounding surfaces: header, the inlet port, valve and cylinder + inlet and outlet. I use extrusion layers thus I also use region based meshing.

My problem is that I have to get the swirl number according to Tippelmann [swirl= (Moment*rho*dzyl/2)/mass_flow^2]. The swirl ratio is not appropriate and I also found no other swirl relevant things. According to the formula I also could use the moment to calculate the swirl myself. However the moment report is based on a surface. Perhaps that works when you can choose a propeller surface or similar but I have only air in the cylinder. When I choose the surface of my cylinder the report gives me the moment produced on the cylinder wall, right?

I was thinking of creating another surface within the region that is orthogonal to the cylinder axis. If I create a new surface within my existing part I do not know how to place it where i want it. Another idea was to create a shape part (cylinder) at the right position and combine it with my original part, delete the unwanted surfaces and merge the left surface with the cylinder surface. It is obvious to me that the second option sounds like a long way around. Is it possible to use one of these options to get what I wanted? If it works, do I have to assign a boundary to it (overset mesh/symmetry plane?)? Does it influence my simulation?

I also tried to find something in field functions to create a user field function that i could use on a plane section. But there were no forces respectively accelerations given I could use.

I´m also open for any other solution.

Thank you in advance and i would be very happy if you can help me.