فهرست مطالب رحیم میرکی باصری

In this research, the optimization of the geometric parameters of the hovercraft skirt is investigated using the PSO algorithm in order to reduce the range of vibrations on the structure and increase the ride quality. At first, the dynamic equations governing the hovercraft in two states of contact with the ground surface and non-contact are presented. Based on the presented nonlinear dynamic equations, the equilibrium point of the hovercraft was extracted and by linearizing the nonlinear dynamic equations governing the heave motion of the vessel around the equilibrium point, the linear form of the governing dynamic equations was extracted. In order to reduce the vibrations and increase the ride quality with the vessel, an objective function is presented, and based on this objective function and using both forms of linear and non-linear dynamic equations, the geometric parameters of the skirt are obtained based on the intelligent PSO algorithm. Finally, it is shown that comparing the frequency and time behavior of the optimized hovercraft with the original hovercraft, the range of vibrations is reduced and the ride quality with the optimized hovercraft is greatly improved.

Estimating dynamic behavior of high-speed Planing vessels is one of the concerns of designers of such vessels. Evaluation of the loading and center of gravity variation effects, for small vessels with different motion modes, are very important at design stages. Such effects, if not taking into account correctly, may affect the final behavior of the vessel. In this research, for investigating the effects of loading and the center of gravity variations on the behavior of a monohull planing boat, a scaled- down 1:5 model was built based on the ITTC standard and Froude method. after the preparation and balance of the model, tests of the model have been carried out in the high-speed towing tank, in calm water and two loading conditions and at four positions of center of gravity. In each run of test (total 40 tests), the resistance, trim and sinkage, have been measured, and the longitudinal and transverse dynamic stability of the model has been qualitatively evaluated. The results show that increasing the weight will increase the resistance. increasing the distance of the center of gravity position from the stern, will reduce the resistance and trim in the displacement mode and increase the resistance in the planing mode. Also, the decreasing the center of gravity distance from the stern, will reduce the resistance and increase the trim in the planing mode, but may results in the longitudinal instability of the model in some extreme conditions.