Approach
–Select number of blades based on frequency of excitation (similar designs).
–Select area ratio based on cavitation limitations: The minimum area ratio allowed by cavitation or strength will have the best efficiency.
–In general, larger diameter is better.
–In general, lower RPM is better.
–If machinery sets RPM, then seek the optimum diameter.
–If stern aperture sets the diameter, seek the optimum RPM.