EXPERIMENTAL AND NUMERICAL INVESTIGATIONS INTO CATAMARAN VISCOUS RESISTANCE

摘要

Investigations into the components of catamaran viscous resistance and viscous interaction effects between the hulls have been carried out experimentally using a low-speed wind tunnel and numerically using a commercial CFD code (CFX). The investigations used bodies of revolution and representative reflex models of multihull ships. The wind tunnel tests were carried out on a single ellipsoid and a pair of ellipsoids in proximity at separation to length ratios (S/L) of 0.27, 0.37, 0.47 and 0.57 and at Reynolds Number values up to 3.2 x 10~6. In the numerical work, investigations were carried out on ellipsoids with the same geometry as tested in the wind tunnel, ellipsoids with a larger length to diameter ratio and reflex versions of two round bilge transom stern hull forms in catamaran configuration with different length/displacement ratios. Further numerical investigations were carried out at the higher Reynolds Number of 1 x 10~8 in order to investigate any scale effects. Results of the wind tunnel tests and numerical investigations are presented and compared. These are in turn compared with results from previously published tank test data. Data from the various approaches are brought together and values of viscous form factors and catamaran viscous interactions for use in practical powering estimates are presented.