In model tests, propellers are usually operated in nominal ship wake to measure exciting forces, and the incoming flow to propellers is different from that when the propeller is working right after the hull, which may lead to different results. Numerical methods were applied for simulations of two experiments: one is to simulate the propeller after a specially designed stern, and the nominal ship wake is set to the velocity inlet boundary, and free surface is considered; the other is to simulate the propeller right after the entire hull model. Results show that the amplitude of axial force of a single blade from the simulation of propeller after the stern is under-predicted, while the amplitudes of transverse and vertical forces of the whole propeller are over-predicted, but the differences are small. The amplitudes of fluctuating pressures on the hull surface predicted by the two approaches are basically the same.