  In this study, the application of surface roughness on model and full scale
marine propellers in order to mitigate tip vortex cavitation is evaluated. To
model the turbulence, SST kOmegamodel along with a curvature correction is
employed to simulate the flow on an appropriate grid resolution for tip vortex
propagation, at least 32 cells per vortex diameter according to our previous
guidelines. The effect of roughness is modeled by modified wall functions. The
analysis focuses on two types of vortices appearing on marine propellers: tip
vortices developing in lower advance ratio numbers and leading-edge tip
vortices developing in higher advance ratio numbers. It is shown that as the
origin and formation of these two types of vortices differ, different roughness
patterns are needed to mitigate them with respect to performance degradation of
propeller performance. Our findings clarify that the combination of having
roughness on the blade tip and a limited area on the leading edge is the
optimum roughness pattern where a reasonable balance between tip vortex
cavitation mitigation and performance degradation can be achieved. This pattern
in model scale condition leads to an average TVC mitigation of 37% with an
average performance degradation of 1.8% while in full scale condition an
average TVC mitigation of 22% and performance degradation of 1.4% are obtained.
