Simulation of Full-Scale Ship Wake Distribution by a Semi-Geosim Model

摘要

Proper evaluation of the cavitation performance of a model propeller requires that as large a propeller as possible be tested so that the deviation in geometric similarity due to fabrication can be minimized. Propeller-tip cavitation inception is known to be Reynolds number dependent. Minimization of the scale effect also requires use of a large sized model propeller to achieve a high Reynolds number. Additionally, kinematic similarity requires that the radially varied inflow distribution at the propeller plane anticipated for a full-scale ship, must be properly simulated in the model tests. However, the geometric dimensions of the water tunnel present a constraint on the model size allowed. These conflicting demands have led to development of a semi-geosim ship model. The present report documents the measured, radially varied inflow distribution at the propeller plane of a semi-geosim model with various combinations of mesh screens on the body surface and lengths of the parallel middle body. Experimental results at the 36-inch(91cm) water tunnel indicate that the target wake of a representative axisymmetric ship body may be reasonably simulated to the propeller tip by a semi-geosim model with a propeller 14 in. (35.6 cm) in diameter. (Author)