Detailed Measurements Of Wave-pattern AndNominal Wake Of A Fast Displacement Ship Model

Abstract

Continuous increase in computer performances allows significant improvements in computational fluid dynamics (CFD). However, a validation of numerical results, by means of experimental data relative to representative test cases, is still needed. The cooperative project between INSEAN and IIHR (Iowa Institute of Hydraulic Research) has been developed to increase the model-scale database for CFD validation in naval applications [1]. The flow around a model of a fast displacement ship has been investigated both numerically and experimentally with particular attention to the case of Froude number (Fr) equal to 0.28. To evaluate scale effect on the flow field, two different model sizes have been tested by IIHR and INSEAN [2]. In this work the wave-pattern and the nominal wake velocity field at Fr=0.28 have been experimentally determined for the model-scale 1/24.8 (Lpp=5.72 m). The wave-pattern has been also determined at Froude number equal to 0.41. Uncertainty assessment [3][4] has been performed at four different longitudinal cuts giving a global uncertainty less than 2.4% of the maximum wave elevation. Therefore, for very small field regions, the global uncertainty can reach the 9.5% where the spatial gradient of the wave elevation is maximum [5]. Velocity measurements in the nominal wake plane have been carried out by five holes Pitot tube. Mean velocity components and total head were evaluated on 960 measurement points. Uncertainty assessment has been carried out giving a satisfactory outcome [6]. The presented results are related to the experiments performed at basin n.2 of INSEAN, 220 m long, 9 m wide and 3.5 m depth.