ABSTRACT

The wake survey of ship model is a typical step in conventional and non-conventional hull hydrodynamic design. Nowadays the adoption of Particle Image Velocimetry for this kind of applications has become feasible and allows to obtain a detailed and reliable picture of the flow field, in particular for the turbulent and the unsteady features. The application of such technique at the INSEAN large Circulating Water Channel is performed in the wake of a ship model with installed propeller. The results of the analysis of the wake in a longitudinal plane for different propeller revolution angles are presented. Advantages and drawback of applying the PIV technique in a large facility are pointed out.

INTRODUCTION

The survey of the wake behind a ship model should be a typical step of the hydrodynamic design of conventional and unconventional hulls. This type of information, which is very important for designing the propulsion system in order to obtain high efficiency propulsion, low radiated flow noise, less cavitation problems, lower pressure fluctuations and vibration induced on the vessel, is nowadays obtained using extensively single point measurement techniques like Pitot tube or Laser Doppler Velocimetry (LDV). Flow velocity measurements are also important for the validation of CFD codes; indeed, a detailed representation of turbulent aspects, especially for separated and unsteady flows, is required for enhancing the accuracy of numerical predictions. The availability of reliable velocimetry techniques contributes to fulfil this goal providing data to be used as guidelines for numerical models improvements as well as databases for their validation. The LDV techniques, which allows a very accurate and detailed analysis of flow field [Di Felice and Lalli (1999)], has improved the analysis of ship wake flows allowing the resolution of the 3D flow field in phase with the propeller with high accuracy.

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