Flow survey of a catamaran model in steady drift

This paper presents the results of velocity field measurements around the Delft catamaran 372 advancing in steady drift course. The purposes of the work are the characterization of the strong vortical structures generated along the keel of each demihull and to provide a valuable experimental data set for CFD benchmarking in severe off design conditions. To this aim, a stereo PIV system has been used to measure the velocity field around the model on several cross planes; two speeds, corresponding to Fr=0.4 and Fr=0.5 and to drift angle, 6° and 9°, have been tested. To prevent damages to the PIV system, measurements were taken only on planes where ventilation and/or air bubble entrapment did not occur. For the same reason, measurements could not be taken at higher Froude and/or drift angle. PIV measurements have been conducted fixing the model at the dynamical trim and sinkage, which have been measured in a preliminary PMM experimental campaign.