Chapter 5 - STEREO PIV MEASUREMENTS FOR THE DELFT 372 CATAMARAN ADVANCING IN STEADY DRIFT CONDITIONS

This Chapter deals with the experimental survey of the flow field around a catamaran advancing in steady drift. The survey was aimed at investigating the dynamics of the keel vortices with particular emphasis on the mechanisms underlying their generation, detachment, evolution and destabilization. Detailed flow measurements were undertaken by Stereo-PIV (S-PIV) at selected cross planes along and downstream of the catamaran. The test matrix consists of two Froude numbers (Fr=0.4 and 0.5) and two drift angles (6° and 9°). In the experiments, the model was kept fixed at the dynamical values of trim and sinkage, as measured in a previous Planar Motion Mechanism (PMM) test campaign. The major topological and kinematical features of the keel vortices are highlighted through the analysis of the mean and fluctuating components of the velocity and vorticity field. A conditional average technique was used to investigate the interaction between the keel-vortex and free-surface in the wake of the model.