Prediction of Pressure Pulses
For ship types with a high comfort level, such as passenger vessels or yachts, and also for ship types with military applications, propeller-induced pressure fluctuations are one of the most important aspects in the propeller design process. Unfortunately, they are also one of the most complicated phenomena occurring in the flow around the ship hull and therefore difficult to predict.
Animation left top: Predicted Unsteady Cavity Sheet, left bottom: Corresponding Pressure Distribution on the Blades, right: Unsteady Pressure Distribution on the Hull.
panMARE can be used for the prediction of propeller-induced hull pressure fluctuations under consideration of cavitation effects. The basic principle is shown in Figure 1. A RANS solver is used to compute the instantaneous effective wake field. This wake field is used as input for the calculation of the pressure distribution and the cavity sheet on the propeller blades. Also the unsteady pressure distribution on the hull is simulated. In order to capture the influence of the propeller on the effective wake field, a body force distribution is passed to the RANS solver as described here.
Figure 2 shows some exemplary results obtained by the algorithm. The method is used here to point out wake scale effects on pressure pulses. The numerical results show a good agreement with the experimental data for the first harmonic. Some deviations occur for the second harmonic. This can be improved by taking the cavitating tip vortex into account.