Measurements of the Velocity Field Around the DELFT 372 Catamaran in Steady Drift

The present work concerns the experimental measurements of the velocity field around a catamaran advancing in static drift. The purpose of this paper is twofold: - firstly the study aims at characterizing the dynamics of the keel vortices generated along the demihulls and their interaction with both the free surface and the breaking vortices; - secondly, detailed flow measurements are used to collect a valuable experimental dataset for CFD benchmarking in severe off design conditions. To reach these goals, measurements are performed on some cross-planes along and downstream of the catamaran, for different Froude and drift angle combinations. In all the tests, the model was fixed at the dynamical values of trim and sinkage, measured in a preliminary PMM experiment. Major geometrical and kinematical characteristics of the keel vortices were documented in the paper though the analysis of the mean and fluctuating components of the velocity and vorticity fields.