An Investigation on Ducted Propellers in Axisymmetric Shear Flow,
INSTITUTO SUPERIOR TECNICO LISBON (PORTUGAL) DEPT OF MECHANICAL ENGINEERING
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To improve the basic understanding of the complex interaction flow phenomena between ducted propeller systems and the ships hull, the effects of radial non-uniformity of the inflow to the ducted propeller were investigated, both numerically and experimentally. The mathematical model is based on the Euler equations for an inviscid, incompressible axisymmetric flow and on the representation of the propeller by an actuator disk. In a vorticity-stream function formulation, the problem is governed by two coupled integral equations which express vorticity transport in the flow and the boundary conditions on the duct and hub surfaces. The numerical solution method employs a discretization of the vorticity field into vortex sheets, which are traced iteratively in a fixed grid. The problem was also experimentally investigated in the Large Cavitation Tunnel of the Maritime Research Inst. Netherlands. A five bladed propeller model, placed inside a duct, was tested behind wire screens, generating a wake velocity profile with axial symmetry. Laser-Doppler measurements of mean axial and radial velocities were carried out at various axial locations upstream and downstream of the ducted propeller. Detailed comparisons between the results of calculations and the experiments are presented and discussed.
- Fluid Mechanics
- Marine Engineering