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

Abstract

Speed and stability are two essential criteria for assessment of planing hull performance. Accordingly, the effects of step shape on these vessels’ hydrodynamic performance and stability are experimentally investigated. Five different models are studied which are based on a high-speed recreational craft and are primarily the same in form and dimensions. One of these models does not have a step, two of them have transverse steps, and two other models have Vee-shaped steps. These five models all have a length of 2.64 m, a beam of 0.55 m, a deadrise angle of 24°, and weigh 86 kg. As the parent model, that is, the non-stepped model is unstable at high speeds, this study is aimed to figure out how different types of steps could prevent this kind of instability. The trim angle, resistance, and lengths of the wetted keel and wetted chine of all these models are reported at beam Froude numbers ranging from 0.43 to 3.44. First, the non-step model is investigated in towing tank tests. The optimum position for the center of gravity of this model is determined to be at a distance of 30% of the model’s length to the transom, which leads to the lowest resistance while the model still remains stable. The models with the aft-wise Vee type and fore-wise Vee type experience the lowest and highest resistance among all studied models, respectively. The steps’ performance appears to be directly related to the ventilation condition at the bottom of stepped models. It is also observed that aft-wise Vee-shaped step leads to the most severe flow separation, and the model with this type of step has the least wetted surface area compared to other studied models.

Numerical Analysis of Resistance Characteristics of a Novel High-Speed Quadramaran

“…Considering the absence of publicly available ship model test results, a V-shaped high-speed boat from the M 1 ship type proposed by Parviz Ghadimi [26] is selected to carry out a comparative study to assess the accuracy of the numerical methods. Table 6 lists the principal dimensions of hull M 1 while Fig.…”

“…The ship type studied in this paper was inspired by a catamaran with a step [16]. Using a step on the hull could separate the water, create a dry section from step to transom, and reduce the resistance at high speed [25][26]. The stepped hull is viewed as two regular hulls following each other closely, so that the catamaran turns into a quadramaran.…”

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

“…In the case of stepped hulls, Sajedi et al [29] probed how a single-stepped hull with a step at 30% of vessel length to its stern performs in calm water and Froude numbers from 0.43 to 3.87. Te efects of vee-shaped steps on the hull's performance and how they difer from transverse steps have been experimentally probed by Ghadimi et al [33]. Sajedi and Ghadimi [28] also experimentally studied the singlestepped hull in the presence of irregular waves.…”

“…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.…”