The relationship between inherent ship manoeuvrability, human factor and environmental condition is often mentioned as very important factors for the safety of navigation and analysis of marine accidents. Especially, the relationship between these three factors becomes more closre and complicated in shallow water. Because of this reason, it is difficult to say what the main cause is exactly. Underneath this situation, the demand for establishing a new guideline or standards of ship manoeuvrability in shallow water have been gradually growing up and researches for the effect of shallow water have been performed. However, the researches such as hydrodynamic forces acting on a ship, mathematical model in shallow water have been performed independently and there are a few researches considering a ship manoeuvring characteristics in shallow water. Therefore, in present study, the authors focus on a ship manoeuvring characteristics in shallow water rather than hydrodynamic forces or mathematical model. In addition, because it have been recently said that the factors of ship form are concerned with the manoeuvring characteristics in both shallow and deep water, the relationship between the factors of ship form and manoeuvring characteristics in shallow water is investigated. In order to investigate these relationship, the numerical simulation of manoeuvring motion in shallow water is performed and compared with the results of model test. And then some results are shown as examples.
Darrieus wind turbine has attractive characteristics such as the ability to accept wind from random direction and easy installation and maintenance. But the aerodynamic performance is proved to be very complicated, especially for the existence of Dynamic stall. How to get a better aerodynamic performance arouses lot of interests in the design procedure of a Darrieus wind turbine. In this paper, we are trying to explore the better choice of some primary design parameters of straight Darrius wind turbine based on numerical investigation. Mounting position on the blade, radius of the wind turbine, tip speed ratio and number of blades together with solidity are mainly focused on. As to the numerical method, the flow around the turbine is simulated by solving the two-dimensional unsteady Navier-Stokes equation combined with continuous equation. The time marching method on a body-fitted coordinate system based on MAC method is used. O-type grid is generated to the total calculation domain. In order to compare the numerical results with the validated results of single-bladed turbine, NACA0015 section is still selected as the wind blade section. The characteristics of tangential and normal force are discussed related with dynamic stall of the blade. Averaged Power coefficient per period of rotating is calculated to evaluate the eligibility of the turbine.