A Method for the Inverse Design of Ducted Propulsors Operating in Axisymmetric Shear Flows

A method is presented for the design of multi-component marine ducted propulsors of arbitrary blade loading operating in axisymmetric shear flow.  An “actuator duct” representation is used, whereby each blade row is assumed to consist of an infinite number of blades of finite axial extent.  Employing a further assumption of inviscid flow and using the Clebsch decomposition of the vorticity, it becomes possible to describe both the propulsor throughflow and bypass flow by partial differential equations in terms of Stokes’ stream function and Clebsch variables.  By modelling the region of flow from far upstream of the propulsor to far downstream into the wake, the effects of slipstream contraction and fully included.  Inputs to the design process include blade shapes, propulsor mass flow, overall thrust, velocities and the duct pressure distribution. Computation results are presented for both ducted propellers and more complicated configurations such rotor-stator and contra-rotating propulsors, clearly showing the effect of rotational inflow on blade shapes and propulsor mass flow.

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