Inhibition and Hydrodynamic Analysis of Twin Side-Hulls on the Porpoising Instability of Planing Boats

Jiandong Wang,Yumin Su,Jiayuan Zhuang,Xiaosheng Bi

doi:10.3390/jmse9010050

Jiandong Wang, Yumin Su + Show 2 more

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https://doi.org/10.3390/jmse9010050

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Abstract

A comparative analysis of the hydrodynamic performance of a planing craft in the monomer-form state (MFS) and trimaran-form state (TFS) was performed, and the inhibition mechanism of twin side-hulls on porpoising instability was evaluated based on the numerical method. A series of drag tests were conducted on the monomer-form models with different longitudinal locations of the center of gravity (Lcg); the occurrence of porpoising and the influence of Lcg on porpoising by the model was discussed. Then, based on the Reynolds-averaged Navier–Stokes (RANS) solver and overset grid technology, numerical simulations of the model were performed, and using test data, the results were verified by incorporating the whisker spray equation of Savitsky. To determine how the porpoising is inhibited in the TFS, simulations for the craft in the MFS and TFS when porpoising were performed and the influence of side-hulls on sailing attitudes and hydrodynamic performance at different speeds were analyzed. Using the full factor design spatial sampling method, the influence of longitudinal and vertical side-hull placements on porpoising inhibition were deliberated, and the optimal side-hull location range is reported and verified on the scale of a real ship. The results indicate that the longitudinal side-hull location should be set in the ratio (a/Lm) range from 0.1 to 0.3, and vertically, the draft ratio (Dd/Tm) should be less than 0.442. Following these recommendations, porpoising instability can be inhibited, and lesser resistance can be achieved.

Highlights

Stability problems associated with high-speed planing crafts have long been a notable research focus for designers, even in calm waters
The results show that the numerical method had good convergence, high accuracy, and appropriate efficiency in sFimiguulartein1g4t.he navigation of the model in calm water
Comparing the amendatory RT with test results, the maximum deviation was −6.53% at Fr = 1.89 when locations of the center of gravity (Lcg)/Lm = 0.35, which proves the calculated results of the RT could be remarkably improved after the correction of the whisker spray equation of Savitsky [27]

Summary

Introduction

Stability problems associated with high-speed planing crafts have long been a notable research focus for designers, even in calm waters. Considering the reasons outlined above and the associated adverse situations, it is important for engineers to control the longitudinal and transverse instability of high-speed crafts. Mehran et al [13] ascertained that the inhibition mechanism of the interceptor on porpoising in the planing boat, and Mansoori et al [14,15] further analyzed the influence of boundary layer thickness, interceptor height, and span on the inhibition of porpoising and navigation resistance, and demonstrated that the combination of trim tab and interceptor with the same size is more beneficial to control the trim and reduce the resistance than the single interceptor. To develop a craft design utilizing an interceptor that included six heights at distinct positions of the stern bottom, Ahmet and Baris [16] tested resistance and sailing attitudes and reported that for the same-size interceptor, the effect of drag reduction and porpoising inhibition was gradually reduced when installed at the interval from keel to bilge line. Hongjie et al [17] and Hanbing et al [18] calculated the porpoising of a planing boat in a uniform incoming flow, indicating that moving forward of the center of gravity could reduce the resistance peak value, which is beneficial to avoid porpoising

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