Experimental Study of the Wedge Effects on the Performance of a Hard-chine Planing Craft in Calm Water

Abstract

In this paper, effects of a wedge on the performance of planing craft in calm water are experimentally investigated. Experiments are carried out on three different cases distinguished by the wedge type. The model, built of fiberglass, is a prismatic planing hull with deadrise angle of 24 degrees. Towing tests are conducted at different Froude numbers ranging from 0.21 to 2.1. The total trim angle, resistance, rise up at the CG as well as stern and bow, keel wetted length, chine wetted length, stagnation angle, and the length of stagnation line are measured. They are used to study the effect of installing a wedge on the performance as well as the effect of height on the hydrodynamic characteristics. Based on the observations made, it is concluded that, when the wedge is applied to the hull, the risk of model exhibiting instability diminishes, while total trim angle largely decreases, keel wetted length is enlarged, wetted surface becomes thinner, CG rise up is lowered, and the resistance is reduced. Moreover, experimental measurements and theoretical 2D+T theory are combined to bring deeper insight about physics of the flow and pressure distribution when a wedge is installed on the bottom of a planing hull.

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.…”

“…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]. For further comparison, previous works related to the current study on planing hulls (especially trimaran) in recent years are presented in Table 1.…”

Experimental study of hydrodynamic performance of a Monohull Planing vessel equipped by combined transverse step and transom wedge in comparison with a model of no appendage

“…Various numerical works have also been done on the physics of turbulent fluid flow [49][50][51]. Ghadimi et al [52] also performed an experimental study on the effect of wedge on seakeeping of planing hulls. As noted above, another purpose of installing appendages like wedge and trim tabs on the vessels is to reduce the resistance and control the trim angle.…”

“…As the flap angle increases, the resistance in the planing regime increases. (2019) Ghadimi et al [71] Experimental study of the effect of wedge on single-body was performed in calm water. (2019)…”

“…The current study addresses this issue. The model without any appendage have been previously tested by Ghadimi et al [52]. The single step model as well as wedged & stepped model are examined in the present study.…”