To long calculation time in external and time dependent nozzle simulation

I’m designing a nozzle and I am having some problems with calculation time.

I am trying to do an external and time dependent simulation but the calculation time is too big (over 20h) and my hardware is good enough (8 cores i7 3770 3.4-3.9GHz and 8Gb at 1866Mhz of ram .

I tried to reduce the computation domain and personalize the mesh. If I reduce the computation domain the calculation time decreases but not enough.

I also tried to disable “Optimize thin walls resolution “ option and “High Mach number flow” option.  If I disable “High Mach number flow” option the calculation time reduces drastically but y need to keep this option enabled.

I am not sure if my personalized mesh has the correct dimensions.

That’s my actual mesh.

I’ll really appreciate your help