Experimental and Numerical Investigation of Stepped Planing Hulls in Finding an Optimized Step Location and Analysis of Its Porpoising Phenomenon

Abstract

Stability of a high-speed craft is an essential matter, and porpoising is one of the most critical instabilities that could occur in some planing hulls due to inappropriate design. In this paper, the porpoising phenomenon and variation of step location yielding resistance reduction are studied through experimental and numerical methods. The investigated models include a single-step model and a nonstep model with the same general shape, but with different step location. The nonstep model is previously tested, but the single-step model is examined in the present study. The nonstep model experiences porpoising at 8 m/s speed, but the single-step model remains stable at the same speed. A three-dimensional CFD analysis is conducted using the finite volume method (FVM). On the contrary, the volume of fluid (VOF) scheme is used for free surface modeling, and the overset mesh technique is implemented within StarCCM+ software. The CFD results of total hydrodynamic resistance and dynamic trim angle are compared against the experimental data. The numerical results are in good agreement with the experimental data. Subsequently, ten different stepped models are simulated to examine their effects. The longitudinal distance between steps and aft of these models are in the range of 19 to 50 percent of the length of models. The obtained results show that as steps are located farther than aft, the models become more stable, and resistance increases due to trim reduction. Finally, the optimum location of the step is extracted with the aim of minimizing the resistance through the design of experiment (DOE) method. Based on the DOE method, it is observed that the sensitivity of the drag value to the step location is higher than the speed.

Experimental Study on Motion Behavior and Longitudinal Stability Assessment of a Trimaran Planing Hull Model in Calm Water

“…The towing test results were extracted and processed, and Figure 5 plots the total resistance, trim angle, and sinkage of the schemes of the bare hull as functions of the volumetric Froude number Fn. In general, the porpoising of a monoplaning hull often arises at a speed no greater than Fn = 5 [19][20][21][22][23], while the conversion Froude number exceeded 7 in the current paper; this indicates that the planing trimaran showed excellent high-speed performance.…”

“…Lu et al studied the coupling action of a stern flap and step on a monoplaning hull, both experimentally and numerically [7]. Sajedi and Ghadimi assumed the wetted surface area as a step height and location function, and by experimental and numerical investigation, the optimal layout and configuration of the step were discussed and extracted with the aim of minimizing the resistance [21]. Furthermore, a series of towing tests were carried out by Ghadimi et al, analyzing the hydrodynamic performance and effect of appendages such as wedges and steps on resistance and stability performance [22,23].…”

Numerical Study of the Effect of Angle and Location of the First and Second Steps on the Performance of Planing Hull and Their Optimization Using the Taguchi Statistical Method

“…Sajedi and Ghadimi [28] also experimentally studied the singlestepped hull in the presence of irregular waves. Supported by these experimental data for single-stepped hulls, Sajedi and Ghadimi [34] tried to fgure out the best location of a transverse step by examining ten diferent steps' longitudinal locations in a numerical efort.…”

“…Tey found that the simultaneous use of stern wedges and transverse steps could improve the vessel's undesirable performance prior to planing regime, which is one of the challenges in planing hull design. Tese extensive data [9,28,29,[31][32][33][34][35][36][37] for diferent confgurations of a single parent model present a unique opportunity to realize how diferent confgurations of step and wedge could afect a planing hull's performance.…”

Experimental study of the effects of Vee-shaped steps on the hydrodynamic performance of planing hulls

“…Caterino and Mancini 23 attempted to find an optimized unwetted aft area behind the steps of stepped hulls, with the aim of drag reduction and dynamic stability improvement. Finding the optimized step location was also pursued by Sajedi and Ghadimi 24 who attempted to obtain the least resistance. Their measurements showed that total resistance of the vessels is more dependent on the longitudinal step location than the sailing speed.…”