hello Mujahid,
Regarding the repeated cycles of infeasible solutions, I think this is because the constraints could be set too tightly. Try changing the upper/lower limits on your design variables to increase the range, and hopefully the code should find more feasible solutions. I think the problem you are facing has been discussed in this thread: HARP_Opt Cavitation Constraint - #5 by Peter.Hourihane My guess is that cavitation constraint is giving you problem, and best way to remedy is to limit the maximum rotor speed. Hope that helps, otherwise you could try describing your input values and error messages in more detail.
~Danny