Study of unsteady hydrodynamic effects in the stern area of river cruisers in shallow water
The main objective of the present paper is the assessment of the influence of shallow water conditions on the hydrodynamic exciters of ship hull vibration using modern hybrid RANS-LES turbulence model. Validation of the computational method was performed for a model of an inland vessel, moving in a shallow channel. Good agreement with PIV measurements for the wake was attained. After the validation the method was applied to analysis of the influence of different factors on the nominal wake characteristics, assessment of thrust fluctuations and pressure pulses and their sensitivity to motion conditions. For the nominal wake significant intensification of the velocity fluctuations was observed, which was caused by the growth of the skeg vortex. Computations with rotating propellers demonstrated, that the depth restriction may influence the periodic forces and moments acting on the ship stern and by these means intensify the vibration. Additionally it was shown, that under investigated conditions cavitation can occur. It is recommended to take the influence of shallow water on vibration exciters into account at the design phase.