Comparative Study Of Ship Wind Load Between The Empirical Formula And The Computational Fluid Dynamics Method

With the development of shipbuilding technology,various kinds of design concepts for marine structures have been moving towards large-scale.Large-scale marine structures are affected by wind loads at sea due to their high center of gravity and large windward area.In this dissertation,the characteristics of wind load with large windward area marine structures were studied.A very large crude carrier and a very large container ships were selected as research objects under various loading conditions.Firstly,the 3D models of the ships were built with SolidWorks according to the ship profile diagram.According to the basic principles of fluid mechanics and related knowledge of computational fluid dynamics,the calculation domain was set reasonably in the numerical simulation software,a targeted meshing method was proposed which was based on the characteristics of the laboratory hardware and the study object.After calculating the boundary conditions and fluid dynamics equations,the numerical simulation method was used to calculate the three direction wind load coefficients of the hull under different wind attack angle.The longitudinal,lateral and yaw wind load coefficients of the ship were compared with the wind load coefficients estimated by the Isherwood formula.As for the very large crude carrier,the main factors causing the deviation of the two ways under different wind attack angles were analyzed according to the aerodynamic principle,and the reasons for the obvious deviation of the yaw coefficient were mainly studied.The analysis and comparison results show that the proposed fluid dynamics calculation method can effectively improve the wind load estimation accuracy of the very large crude carrier.The wind load results of the container ship under various loading conditions was compared with the Isherwood formula estimation result,it was found that the empirical formulas have different degrees of underestimation of the wind loads received by the large container ships as the ship’s load changes.Combined with the numerical simulation of the hull surface wind pressure,the air flow line near the hull and the surrounding wind field pressure cloud map analysis.Computational fluid dynamics numerical simulation experiments can be used to obtain the hull surface wind pressure diagram,the air flow line diagram near the hull and the surrounding wind field pressure contour diagram,it showed that the container shielding effect is obvious and the bluff body effect formed by the container rules are the main causes of the increase of ship wind load.The reason and the complicated distribution of the low-pressure wind field on the leeward side may further aggravate the deviation of the conventional formula estimation.At the same time,due to the flow around the bluff body of the container ship,the yaw moment under the wind load is increased,which makes the elongated hull of the container ship more susceptible to torsional deformation.The study we have done in this dissertation can provide a certain reference for guiding the wind-resistant design of such ships and provide corresponding guidance for the safe operation of ships in a strong wind environment.