Michell’s Thin Ship Theory in Optimisation of Warp-Chine on Pentamaran Configuration

Abstract

This study was conducted to optimise warp-chine pentamaran configurations in wave cancellations to a significant total resistance reduction for a wide range of speed. The optimisation of a pentamaran with a warp-chine hull form was performed by a computer program Godzilla based on Michell's theory and validated by the towing test. The distance parameters of the outrigger were evaluated to select the lowest resistance generated. Computational analysis depended on the Michell-based tool compared to a commercial Computational Fluid Dynamics (CFD). The comparison of the measurement test of the total resistance and Michell's calculation results of all configurations showed a suitable trend, especially at Fn ≥ 0.4. However, it was not satisfactory for CFD trend. The illustrated of far-field wave pattern by the Michell-based instrument also consistent with the wave spectrum that captured in the test. The results of the analysis and observations revealed that the test measurement for all configuration models in the same estimated error (uncertainty) range of the total resistance. This optimisation has confirmed the stagger at the range of 0.36L-0.42L where the front outriggers and the after outriggers not in line of clearance as in arrow formation significant in wave cancellation and resistance reduction.

Achieving Drag Reduction with Hullform Improvement in Different Optimizing Methods

“…Due to the COVID-19 pandemic, high-speed testing was not conducted. However, the first authors (Sulistyawati et al, 2020c) proved that the Michell integral method is quite precise with test results at higher speeds above Fr 0.4. Analysis of pentamaran configuration were optimized with the Michell integral method and were closer to the test results than the Reynolds Averaged Navier Stokes equations by Computational Fluid Dynamics or called RANS-CFD (Figure 4b).…”

“…The Michell integral method or thin ship theory is considered a more straightforward and faster CFD method (Tuck and Lazauskas, 1998). Several studies (Yanuar and Sulistyawati, 2018;Sulistyawati et al, 2020a;Sulistyawati et al, 2020b;Sulistyawati et al, 2020c) used Michell theory to investigate the hydrodynamic characteristics of pentamarans and compared them with experiments. Any deviations from the Michell integral method were deemed necessary for development.…”

“…The hull is defined by inputting data with a grid offset setting into 21 stations and 21 water lines, a genetic algorithm in multi-objective optimizations to approximate the optimized hull with a minimum wave and total resistance in calm water. Two simple tools based on Michell's theory were quite applicable for investigating resistance performance and optimization (Sulistyawati et al, 2020b;Sulistyawati et al, 2020c). The results were compared with the Rankine source method (Zhang and Zhang, 2015).…”

“…Lines plan of hull Series 60 with offset set of hull station and waterline Wave resistance coefficient (CW) based on: (a) Michell integral; and (bComparison of Michell's integral method and study of (Zhang and Zhang, 2015): (a) wave resistance, CW; and (b) total resistance, CT Comparison of: (a) wave resistance, CW, and total resistance, CT, of hull series 60; and (b) optimization with the Michell integral method, test results, and RANS-CFD(Sulistyawati et al, 2020c) …”

Full-Scale CFD Analysis of Double-M Craft Seakeeping Performance in Regular Head Waves

“…Waskito et al [24], also studied interference effects on calm water resistance performance of pentamaran using experiments for Fr = 0.3-0.9 and noted that to produce meaningful changes in resistance, hull separation values should also be increased significantly. Sulistyawati and Pamitran [25] applied Michell's thin ship theory on several different hull arrangements for the resistance optimization and the numerical results are compared with experimental ones. In addition to the fundamental studies in the literature about Double-M craft and pentamaran hulls, the resistance and seakeeping analyses will be carried out on a new, transversely arranged Double-M craft multi-hull of an award-winning Emergency Response and Rescue Vessel (ERRV) design to determine its feasibility under various wave condition and forward speeds.…”