考虑相干性海洋结构风-浪联合作用力一种计算方法

Calculation method of wind-wave joint forces exerted on offshore structures considering coherence

随机风、浪环境要素之间存在较强相干性,该相干性影响风、浪联合传播过程中脉动风速与波浪形态,进而影响海洋结构风-浪联合作用力及结构响应。为准确计算结构随机风-浪联合作用力,基于已建立的描述随机风、浪联合传播相干性的风-浪相干函数,计算获取海洋结构来流脉动风速与入射随机波面之间互相关谱,建立包括风速自谱、风速互谱、波浪谱及风-浪互谱在内的结构随机风-浪联合功率谱矩阵。基于联合谱矩阵的Cholesky分解矩阵,利用谐波合成方法生成风、浪相互作用下的结构来流脉动风速时程,进而结合结构水上部分风阻系数生成结构脉动风作用力时程;基于联合谱矩阵的Cholesky分解矩阵,通过谐波合成计算式中引入结构随机波浪作用水动力传递函数的方式,生成风、浪相互作用下的结构随机波浪作用力时程。联立生成的随机风、浪作用力时程即可建立结构随机风-浪联合作用力同步时程。以直立圆柱风-浪联合作用力计算为例,开展了以上算法的算例应用分析。

There is stronger coherence between environment elements of random wind and wave,it affects fluctuating wind speed and wave form in wind-wave joint propagation process to further affect wind-wave joint forces and structural responses of offshore structures.Here,to correctly calculate random wind-wave joint forces exerted on structures,based on the established wind-wave coherence function describing random wind-wave joint propagation coherence,the cross-correlation spectrum between fluctuating wind speed exerted on ocean structures and incident random wave surfaces was calculated and obtained.The structural random wind-wave joint power spectral matrix was established including wind speed self-spectrum,wind speed cross-spectrum,wave spectrum and wind-wave cross-spectrum.Based on Cholesky matrix decomposition for the joint power spectral matrix,the harmonic synthesis method was used to generate fluctuating wind speed time histories exerted on structures under wind-wave interaction,and then the wind resistance coefficient of structure upper parts was combined,fluctuating wind force time histories exerted on structure were generated.Based on Cholesky matrix decomposition for the joint power spectral matrix,the structural random wave action hydrodynamic transfer function was introduced into the harmonic synthesis calculation formula to generate structural random wave action force time histories under wind-wave interaction.Synchronous time histories of structural random wind-wave joint action forces were established by jointly arranging the generated random wind time histories and the generated random wave time histories.Taking calculation of wind-wave joint forces exerted on an upright cylinder as an example,the application analysis of the above algorithm was performed.