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An excessive trim by stern on a high-speed craft is vulnerable to decrease comfortable ride incorporated with the large pitch motion. To prevent such problem, the craft is then equipped with a device known as “trim-tabs” providing a lift force at the stern region, which leads to reduce pitch angle/trim of the craft. This paper presents computational modelling of trim-tabs on high-speed craft towards reducing the pitch motion in the calm water condition. Here, the commercial Computational Fluid Dynamic (CFD) software; called Numeca Fine Marine has been accordingly utilised to evaluate several effects of Froude numbers (Fr) and angle of the trim-tabs into characteristics of the lift force of the high-speed craft. The results revealed that the pitch motion of the high-speed craft equipped with the trim-tabs (5o) has significantly reduced up to 76% at Fr = 1.0. This can be explained that the installed trim-tabs has increased the negative trim moment, which inherently creates the restoring moment pushing the stern up along the pitch-axis. Meanwhile, this may cause involuntary the total ship’s resistance increased. In general, this simulation pointed out the advantage of the trim-tabs to increase the comfortability of the high-speed craft.

Predicting ship resistance in shallow water conditions is very important for the operational considerations of a ship. Shallow waters greatly affect viscous resistance, wave resistance and also propulsion efficiency. This study aims to determine the effect of water depth on the resistance of the ferry. The CFD method was used to simulate this phenomenon and its effects on the hull starting from the coefficient of ship resistance, surge force, sway force and yaw (hydrodynamic moment). Input speed at 9 – 13 knots with depth ratio H/T = 4 (deep water), H/T = 3 (deep water), H/T = 2 (medium water), H/T = 1.3 (shallow water), and H/T = 1 (very shallow water). The simulation results show a significant increase in total resistance, surge force, sway force, and hydrodynamic moment in shallow water conditions in every speed variation. This condition is caused by the increase in pressure received by the ship's hull when operating in shallow water.

The characteristics of the fore and aft foils at the various angles of attack incorporated with forward velocities have been vulnerable to induce strong nonlinearities to dynamic lift force and ship resistance. Then, a computational simulation is necessarily required to predict their performances in the calm water condition. This paper presents a computational investigation of the hydrofoil ship on predicting lift and ship’s resistance using fluid dynamic (CFD) simulation approach. Several parameters such as Froude numbers and the angle of attacks both of fore and aft foils have been accordingly taken into account. The results revealed that the subsequent increase on angle of attack of fore and aft foils was directly proportional to the lift force and the ship’s resistance. In addition, the lift force of the aft and fore foils with the angle of attacks of 10 degrees and 5 degrees, respectively, resulted in the significant increase of the lift force and the ship’s resistance. However, the subsequent increase of Froude number from 1.382 up to 1.626 has insignificant effect to the lift and the ship’s resistance of the hydrofoil. It can be concluded that CFD simulation is very beneficial to ensure an operational effectiveness of hydrofoil design towards prediction on the lift force and the hydrofoil’s resistance at the preliminary design stage.

Due to the increasing of fuel prices and volatile of environmental regulations, it is a challenge for Naval Architects to design a ship dealing with an optimum ship’s total resistance. The conventional design of catamaran hull has not satisfied yet to reduce the ship’s total resistance. This paper presents a numerical investigation into gaining sufficient reduction of the ship’s total resistance of catamaran through optimizing her hull form. To achieve this research objectives, a numerical optimization modelling coupled with a Computational Fluid Dynamics (CFD) approach has been successfully conducted. Several parameters such as length, beam and draft of catamaran hull have been taken into account towards reducing the ship’s total resistance. Here, the simulation constraints are applied to obtain the optimum dimension, where the length, beam and draft of the catamaran hull were optimized within the range of 1.2 m to 1.5 m, 0.11 m to 0.14 m and 0.07 m to 0.08 m, respectively. In general, the optimization simulation revealed that the optimum dimension of the catamaran hull resulted in reduction of the total ship’s resistance. The results showed that the optimum length, beam and draft of hull led to reduce by 21.08%, 16.95% and 17.91%, respectively. Merely, this numerical optimization simulation provides a useful way for reducing the total ship’s resistance of the catamaran at the preliminary design stage.