how to solve large scale problem
 

I am trying to use SIMPLE algorithm to simulate a 2D flow in micro rectangle pipe. I set up the constant pressure values as inlet and outlet boundary condition and two side is no slip wall. The large scale differences between pressure and size of the pipe leads to the results that it converges only if the step time is very very small(10e-9s). Who could tell me which software can solve my large scale problem in order to improve the time step to 1s~0.0001s?