海上风机动冰力模型试验相似律研究

Similarity law study of the ice force model experiment for offshore wind turbines

相似律在模型试验中发挥着非常重要的作用,虽然目前静冰力模型试验的研究比较全面,但还没有一个完整适用的动冰力相似律作为动冰力模型试验基础。本文针对冰激结构振动中动冰力模型试验相似律,基于弹性相似与柯西(Cauchy)相似的联合相似准则,提出了两种动冰力相似律。建立并改进了能够反映冰与结构水平相互作用的相互作用系数。以NREL5MW单桩海上风机为例,通过是否考虑截面弯曲刚度相似分别给出了两种海上风机在海冰作用下原型与模型的相似关系。利用ANSYS/LS-DYNA有限元方法对原型和模型风机进行数值模拟并开展海冰作用下结构的动力响应分析。根据计算结果,基于不同冰厚的冰-海上风机相互作用分别对提出的两种动冰力相似律进行验证,并对两种相似律进行对比。结果表明,后者考虑了弯曲刚度相似虽然可以优化管壁厚度比尺,为模型加工提供方便,然而模拟精度不如前者。研究成果可为寒冷海域冰力模型试验的研究提供理论参考。

The similarity laws play a very important role in model tests.Although the current research on static ice force model tests is relatively comprehensive,there is still no fully applicable dynamic ice force similarity law as the basis of dynamic ice force model tests.This paper proposes two dynamic ice force similarity laws based on the joint similarity criterion of elasticity similarity and Cauchy similarity for the dynamic ice force model test in ice-induced structural vibration.The interaction coefficient that can reflect the interaction between ice and structure is established and improved.Taking the NREL5MW monopile offshore wind turbine as an example,two similar relationships between the prototype and the model of the offshore wind turbines under the action of sea ice are given by considering whether the bending stiffness of the section is similar.Using the ANSYS/LS-DYNA finite element method,the prototype and model wind turbines are numerically simulated and the dynamic response analysis of the structure under sea ice is carried out.According to the calculation results,the two proposed dynamic ice force similarity laws are verified based on the ice-wind turbines interaction with different ice thicknesses,and the two similarity laws are compared.The results show that although the pipe wall thickness scale can be optimized based on the second similarity law which considers similar bending stiffness,and can provide convenience for model making,the simulation accuracy is not as good as the first law.The research results can provide a theoretical reference for the study of ice force model tests in cold seas.