THE COMPUTER-AIDED FUNCTIONAL DESIGN OF A MARINE PROPELLER

An existing propeller geometry is represented mathematically using a method for computer-aided design known as the partial differential equation method. Using this method of surface design ensures that the propeller blade is completely defined and controlled by a small set of design parameters. This geometry may be analyzed using a panel method to obtain the flow past the blade, and a performance measure, in this case the efficiency of the propeller, is obtained. Functional design of the propeller is achieved by allowing the design of the propeller to change. Altering the design parameters will affect the efficiency, and hence the set of design parameters which gives a propeller geometry of maximum efficiency is sought. This is achieved automatically through a numerical optimization routine which alters the design parameters. The advantage of this approach is that complex geometries may be represented in terms of a small parameter set which enables the effective implementation of the optimization routine. Constraints may also be imposed to maintain feasible designs. In the case considered the usual design constraints to delay and restrict the onset of cavitation are imposed. However, additional requirements, requiring in themselves substantial analysis, such as strength of the blade, may be considered.