pathline difference in fan for 1 order and 2 order scheme
 

Hi, I am trying to simulate a fan. In my case, the full 3D fan is modeled with the casing together.

The upstream of the fan is an air chamber and set as pressure inlet 0 Pa. the downstream is set as pressure outlet 0 Pa. The rotating fan is set as MRF. SST model is used.

At first, the rotating speed is increased step by step, the first order upwind for k, omega and momentan equations and 10 times smaller under relaxation factor are used. The pathlines are reasonable, figure 1. Then, the calculation runs under 2 order upwind, but the pathlines are greatly differnce from the figure 1, s. figure 2. It seems the blowing of the fan does not continue.

Can anyone tell me the possible reasons for the simulations?

Thank you in advance!

does anyone have an idea?
thank you!