Experimental measurement of the nearfield longitudinal wake profiles of a high-speed prismatic planing hull

Abstract

This study details an extensive investigation into the nearfield longitudinal wake profiles of a high-speed planing hull. Developing a more thorough understanding of the flow in this region is of benefit to the designers of stepped hulls, who are required to determine how the forebody's wake will intersect with the afterbody. As no experimental data was available within the public domain, a novel small-scale model-testing program was undertaken, measuring Centreline (CL) and Quarter Beam (QB) nearfield longitudinal wake profiles, as well as the resistance, lift and trimming moment of a prismatic hull. The nearfield wake profile was found to exhibit trends in agreement with the findings of previous work investigating the mid and far field wake patterns. The results of this experimental work are provided in full as validation data. Two methods of modelling these profiles, Savitsky's Wake Equations and the Linear Wake Assumption are then assessed to determine the level of confidence with which they may be used. It was found that Savitsky's Wake Equations displayed a surprising level of accuracy whereas the Linear Wake Assumption was not valid for the conditions investigated.

Numerical Modelling of the Nearfield Longitudinal Wake Profiles of a High-Speed Prismatic Planing Hull

“…The wake profile plots are presented in a format consistent with those as presented by [10], with the origin representing the point where the keel meets the transom and the horizontal axis in line with the keel, as seen in Figure 6. The distance aft of the transom, and height of the wake profile, have been nondimensionalised by beam on all figures.…”

“…The global methodology of the project was broken down into two stages. The experimental work as performed by [10] was to be used as validation data:…”

“…The results were then assessed both quantitatively and qualitatively to provide a detailed assessment of the accuracy of CFD. As the paper [10] from which the experimental data was obtained also investigated the accuracy of Savitsky's Wake Equations and the Linear Wake Assumption comments will also be made towards the accuracy of CFD in relation to other methods.…”

“…The second example of an experimental investigation into the nearfield wake of a planing hull was conducted by Gray-Stephens et al [10]. This paper set out to determine the accuracy of the empirical wake equations derived by [2] when they were employed out with their published range or applicability.…”

“…The experimental results were obtained from [10]. Please refer to this paper for detailed discussion upon the experimental set up.…”