圆柱体涡激振动缩尺实验的相似关系研究

Abstract

提出了一种基于雷诺相似的圆柱体涡激振动(VIV)实验方法。涡旋的泄放模式与雷诺数Re密切相关，目前圆柱体涡激振动的研究中，缩尺模型实验往往基于弗汝德相似而雷诺数不相似，因此，模型与原型的涡泄模式不同，由此可以推断，模型的涡激振动响应与原型不相似。这就意味着基于弗汝德相似准则的模型实验结果不能准确地预测原型的涡激振动响应。对基于雷诺数相似的模型与原型的涡激振动实验相似关系进行了推导，采用CFD方法对原型和3种不同相似准则条件下的缩尺模型进行了涡激振动仿真计算, 同时引入实验进行对比。数模结果表明，仅满足雷诺数相似的模型与原型的涡泄模式相似，这个结果与弗汝德数和雷诺数均相似的结果一致，而仅弗汝德数相似条件下，模型与原型之间的涡泄模式和尾流场完全不同。实验结果表明，仅满足雷诺数相似时，模型与原型涡泄周期满足相应缩尺比，而仅满足傅汝德数相似时，模型与原型涡泄周期不满足相应缩尺比。因此，缩尺实验中仅满足傅汝德数相似模型的涡激振动特性不可能与原型相似，应采用雷诺相似准则。An experimental method, based on Reynolds number similarity, of the vortex-induced vibration (VIV) of circle cylinders is proposed to achieve VIV similarity between prototype and tested model. The VIV response of a circle cylinder is closely related to Reynolds number because the mode of vortex shedding highly depends on Re. However, the scaled model test of circle cylinder’s VIV is designed based on Froude number similarity but Reynolds number is not similar under the same fluid for both model and prototype. Therefore, the VIV response of tested model is not similar to that of the prototype because they have different vortex shedding modes. It means that the test results can not be used to predict the VIV response of the prototype according to the scaling law based on Froude number similarity. The prototype and three scaled models with different simi-larity schemes have been simulated using CFD to validate the method and at the same time, expe-riments are compared. The numerical results show that the similarity between prototype and model is satisfying by Reynolds number similarity, and it is in accordance with both Froude number and Reynolds number similarity. But the similarity between prototype and model is not satisfying by Froude number similarity. The experimental results show that the similarity of period of the vortex shedding is satisfying by Reynolds number similarity but not satisfying by Froude number similarity. As a result, Reynolds number similarity should be used in the scale model test instead of Froude number similarity when studying the characteristics of VIV.