目标海域中航行船舶横摇谱密度值的预报策略

Prediction strategy of roll power spectral density value of a ship sailing in a target sea area

横摇功率谱密度的预报是船舶耐波性分析的重要环节。本文以带有舭龙骨的船舶模型DTMB 5512为研究对象,采用CFD方法对船舶横摇频率响应进行计算。首先利用重叠网格法建立船舶在自由液面中横摇运动的数值模型,进而在可靠验证的基础上,数值研究航速、遭遇频率和波浪方向对船舶横摇响应的影响;接着,基于P-M波谱公式推导出海浪自相关函数表达式,结合目标海域的海浪数据对其进行参数修正,获取该目标海域的自相关函数,从而得到目标海域海浪谱;最后,将频率响应谱与该目标海浪谱相结合,得到横摇谱密度。

The prediction of roll power spectral density is important for seakeeping analysis of ships.In this paper,with the model of DTMB 5512 equipped with bilge keels taken as the research target,the rolling frequency response spectrum of the ship was calculated by CFD method.Firstly,the numerical model of ship roll motion with free surface was established by using the overlapping grid method while the verified numerical model was employed to study the effect of ship speed,encounter frequency and incoming wave angle on the ship roll motion.Secondly,an autocorrelation function of the wave data in the target sea area was obtained by properly modifying the parameters of the analytical expression of ocean wave autocorrelation function,which was derived based on the P-M(Pierson-Moskowitz)spectrum formula.Finally,the rolling spectrum density was obtained by combining the rolling frequency response spectrum with the wave spectrum of the target sea.