2002

Pylkkänen, Jaakko

This report reviews the accuracy of methods developed to predict propeller induced hull excitation. Unsteady lifting surface codes often provide acceptable prediction results for unsteady pressures induced by conventional propellers with reasonable computing efforts. In the 1990's unsteady panel method codes have been developed into rather reliable tools for predicting the unsteady pressures induced by conventional propellers. A few organisations have applied unsteady Reynolds-Averaged-Navier-Stokes (RANS) equation codes to the analysis of hull-propeller interaction flow. Free water surface and cavitation were not modelled in these interaction flow calculations. Several research groups are currently developing RANS equations codes to model cavitation. In spite of the recent developments of the numerical prediction methods for cavitating propellers, there are still uncertainties in the estimates for propeller induced hull-pressure fluctuations using theoretical calculations. Therefore, model measurement of hull pressure fluctuations in a cavitation tunnel is the most reliable method to estimate the ship scale hull pressure performance. The difficulties in the simulation of ship scale wake field are one of the major sources of the scatter in the predicted fluctuating hull pressures. For a new type unconventional hull form and/or for a new type unconventional propulsor concept, it can happen that the prediction accuracy is substantially worse than for conventional hull/propulsor concepts for which the method has been validated. This report also reviews statistical methods developed for early design stage use. Published evaluations of statistical methods are summarised.