Sensitivity Analysis Of Ship Form Parameters Based On CFD

The hull shape is the main factor affecting the ship resistance.The hull shape parameters define the hull shape.The sensitivity analysis of hull shape parameters to the ship resistance is very important.At present,the research on the influence of ship form characteristic parameters on resistance mainly focuses on the influence of main dimensions and ship form coefficients on total resistance and the influence of bow shape parameters on wave-making resistance,while the research on the influence of stern parameters on resistance and the influence of each parameter on resistance components is relatively scarce.Therefore,this paper takes the improved DTMB5415 as the research object,carries out the sensitivity analysis of the stern parameters of the ship type to each resistance component.Through CAESES software,DTMB5415 is modeled with full parameterization.In the process of modeling,the model is modified according to the need,and an improved DTMB5415 is obtained.Three parameters of stern lift point,fullness coefficient of rear cross section and stern sink are selected as design variables,and the range of parameters is determined to form design space.Sample points are extracted from design space by Sobol sequence sampling method to generate a series of ship types.SHIPFLOW software is used to calculate the resistance of a series of ships with Fr=0.28 and Fr=0.42 respectively.The calculation accuracy is verified by comparing the calculated resistance of KCS ship with the test results.Based on the calculated data,regression analysis and approximate model method are used to analyze the sensitivity of the selected ship type parameters to the resistance coefficients,and the sensitivity values of the parameters are obtained,and the influence of speed on the sensitivity results is analyzed.In addition,because there are few studies on the rising point of the stern,and the rising point of the stern is more sensitive from the sensitivity results,in order to further study the influence of the rising point position of the stern on the resistance performance,the longitudinal position of the rising point of the stern is changed separately in this study,and the variation of the resistance coefficients with the vertical position of the rising point of the stern is obtained when Fr = 0.28 and Fr = 0.42.The results are as follows: when Fr = 0.28 and Fr = 0.42,the parameters most sensitive to the friction coefficient are the stern lift point,while the parameters most sensitive to the viscous pressure resistance coefficient are the stern sink depth;when Fr = 0.28,they are sensitive to the wave-making resistance coefficient and the total resistance coefficient.When Fr=0.42,the stern depth is the most sensitive parameter to the wave-making resistance coefficient,while the fullness coefficient of the rear cross-section is the most sensitive parameter to the total resistancecoefficient.The interaction of the parameters also has a certain sensitivity value,and the contribution of individual interaction items to the resistance value is more than 10%.The resistance coefficients all follow the stern.The forward displacement of the lifting point decreases,and the friction resistance coefficient and viscous pressure resistance coefficient decrease in the same extent at different speeds,while the wave-making resistance coefficient and total resistance coefficient decrease in different ranges.The results show that the three ship parameters selected have different sensitivity to different drag coefficients.The sensitivity values are influenced by the speed of the ship,and the position of the stern lifting point has a certain influence on the drag performance,and the degree of influence is also different at different speeds.