Hi,

While doing In-cylinder application, I came across with some interesting findings. I am tring to simulate ideal compression process in 3D cylinder. After defining all In-cylinder parameters and zones details; I have solved the same case study with two different approach. In first one I gave the numebr of substeps in each timestep equal to 10 and in another one I gave 40. In both the cases, I found that the difference in maximum temperature is around 120 K ! which is amazing.

Above this in both the cases the maximum temperature achieved after compression is not matching with the value that calculted using analytical formula. My question is how to select the number of substeps which will give the approproate results for in-cylinder application? Has any body come across such situation? Can any one share his/her thoughts on this.

Regards, Yogesh

number of time steps varies inversely to the time step size as far as i can recall doing an unsteady flow. The time step size is more significant a parameter than number of time steps. You would want to control the time step size and then calculate the number of time steps. There is a threshold value that you can calculate for a time step size using any of the CFD books available.