Wind tunnel investigation of a pair of ellipsoids in close proximity

The results of wind tunnel experiments on a pair of ellipsoids in close proximity are presented. The experiments represented a reflex model of a multihull ship and investigated the components of viscous drag and viscous interaction effects between the hulls.The tests were carried out with and without turbulence transition strip at separation to length (S/L) ratios of 0.27, 0.37, 0.47 and 0.57 and at Reynolds Number values up to 3.2 x 106. Tests were included with a single-hull configuration with which the resistance characteristics of the twin-hull configuration could be compared.Results are presented for each S/L configuration as drag and sideforce coefficients at zero incidence. Surface pressure distributions over the hull were also obtained in order to provide a detailed knowledge of the distribution of forces over the hulls.The overall drag coefficients and pressure distributions were comparable with previously published data for single bodies of revolution in isolation. The results with two bodies demonstrated the existence of a viscous drag interaction between the bodies, and that this interaction is maintained at an approximately constant level up to about S/L = 0.5