Experimental and numerical investigation of slamming loads on high-speed craft including hydroelastic effects

Abstract

This thesis investigates the problem of slamming loads on high-speed planing craft and related global rigid body and local structural responses using numerical simulations and full-scale tests. The aim of this work is to improve the safety and efficiency of high-speed craft structural designs for realistic operational loads.
A numerical model for simulating the water impact of two- and three-dimensional rigid and flexible structures is developed. The model uses the commercial CFD software Star CCM+ to solve for the fluid flow and the FE code ABAQUS to solve for the structural response. Two different water entry problems are studied - the water impact of a free-falling rigid wedge and the constant velocity water entry of a flexible composite panel - and the results are compared with the experimental data of Lewis et al. (2010) and Allen & Battley (2015), respectively, for validation. The influence of several numerical and experimental parameters on the solution, including grid and time step size, fluid compressibility, three-dimensional effects, structural boundary conditions and hydroelastic effects, is investigated. The model is then applied to simulate the full-scale drop tests of a realistic hull, also conducted within the framework of this thesis, and the results are compared with the measured data for validation. The effect of three-dimensional flow and spray rails is investigated.
Full-scale rough water trials and drop tests on a 9.6m high-speed planing craft have also been performed. Measurements of rigid body motions, accelerations, pressures, strains and global hull deflections were made for various sea conditions, speeds and headings (rough water trials) and drop heights (drop tests). Methods for processing the experimental data, including low pass filtering the acceleration signals, removing baseline drifts from the strain signals and identifying the peaks in the pressure and strain signals are developed and successfully applied. Characteristic results from the rough water trials including, segments of the time signals, histograms of the identified peaks, calculated averages of the largest 1/3rd and 1/10th peak values, and the loads and responses recorded in a typical impact event, and characteristic drop test measurements are presented and discussed. The repeatability and symmetry of the drop test is also investigated. Statistical analysis of the rough water trials measurements is also performed. The Weibull and generalized Pareto models are fitted to the samples of identified pressure and strain peaks for estimating extreme loads and responses. Automated algorithms for fitting the statistical models to the peak value distributions are developed and the goodness-of-fit of the models to the data is examined.
The suitability of the design loads used in current practice is assessed by comparing the acceleration and pressure measurements from the rough water trials with the predictions based on the ISO (2008) standard and DNV GL (2015) and Lloyd’s Register (2016) rules. Preliminary comparisons between pressure and strain measurements from the rough water trials and the drop tests measurements are also made to examine the relationship between the two tests.

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ORCID for Pandeli Temarel: orcid.org/0000-0003-2921-1242

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