Experimental investigation of the effect of two steps on the performance and longitudinal stability of a mono-hull high-speed craft

Abstract

Transverse steps in modern high-speed craft can increase the longitudinal stability in addition to reducing frictional resistance. The porpoising instability can also be avoided by selecting the appropriate location and height of the transverse step. In the current paper, a non-step and a double-step model are investigated. The primary purpose of the present study is to examine the impact of second step on the stability and performance of the craft. Both models are generally identical. They are prismatic with a deadrise angle of 24 degrees, made of fiberglass, and are 2.64 meters long and 0.55 meters wide. The only difference between the two models is the bottom shape. One has two transverse steps, and the other has no step. These models are tested in a towing tank within a range of beam Froude numbers of 0.43 to 3.87. Measured parameters include rise-up of the bow and aft as well as center of gravity, trim, and resistance of the models. The obtained results indicate that through creating the second step, the longitudinal stability of the model increases, and the trim decreases. On the other hand, the double-step model has lower resistance in the pre-planing state.

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

“…Te authors have previously tested a double-stepped confguration of the parent model in a towing tank [35]. Te four design parameters for steps locations and angles in double-stepped hulls are shown in Figure 2.…”

“…Furthermore, Sajedi and Ghadimi [35] conducted other experiments to investigate the performance of a doublestepped hull with steps at 15% and 30% of vessel length to the stern in Froude numbers ranging from 0.43 to 3.87. Te step location efects in double-stepped hulls with transverse steps at speeds of 10 and 12 m/s were also numerically investigated by Ghadimi et al [36] and validated by some experimental tests.…”

“…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

“…In addition, different inputs must be considered in the computational process. The governing equations for the resistance are given in equations ( 10)- (12). These equations are a combination of coefficients of friction resistance and total strength.…”

“…Concerning the double-stepped hulls, Lee et al 11 determined the role of step height in the performance of double-step hulls by testing seven different hull configurations. Sajedi and Ghadimi 12 also extended their experimental investigation to the double-step hulls. Their measurements demonstrated that, in addition to promoting longitudinal stability, the double steps are also beneficial in the pre-planing regime by reducing the resistance.…”