基于熵产理论的三维涡激振动低速水流能俘能分析

ENERGY CAPTURE ANALYSIS OF THREE-DIMENSIONAL VORTEX-INDUCED VIBRATION OF LOW-SPEED WATER FLOW BASED ON ENTROPY PRODUCTION THEORY

以刚性圆柱作为俘能结构,通过强流固耦合数值方法模拟俘能结构在低速水流环境下的三维涡激振动,对共振约化速度(U_(r)=2~12)范围内进行俘能结构的俘能大小及俘能效率分析。为获得俘能结构三维尾流对俘能大小的影响,采用熵产理论并结合尾流特性以捕捉俘能结构尾涡的能量损失来源及分布,获得不同振动分支下俘能大小与尾流耗散间的关系。结果表明,基于熵产理论的能量损失分析可准确捕捉到俘能结构的能量耗散趋势。黏性熵产主要发生在圆柱表面,湍流熵发生在耗散率较大的尾流区。随着约化速度的增加,上端分支内,当U_(r)=6时俘能结构的俘能效率最大达到30.5%,俘能结构俘获的水动能增加,圆柱表面的黏性熵损耗和圆柱周围及尾流区湍流熵产损失也增加,俘能结构表面的黏性熵产损失和尾流区湍流熵产损失增大成为俘能效率下降的主要原因。

In this paper,the rigid cylinder is used as the energy-capture structure,and the three-dimensional vortex-induced vibration of the energy-captured system in the low-speed water flow environment is simulated by the strong fluid-solid coupling numerical method.The captured energy quantity and the energy capture efficiency of the capturing structure is analyzed in the range of resonance reduction velocity(U_(r)=2-12).To obtain the effect of the three-dimensional wake of the energy captured structure on the captured energy,the entropy production theory and the wake characteristics are used to capture the energy loss source and distribution of the wake vortex of the energy capture structure,and the relationship between capture energy and wake dissipation under different vibration branches are obtained.The results show that the energy loss analysis based on the entropy production theory can accurately capture the energy dissipation trend of the energy-harvesting structure.The viscous entropy production mainly occurs on the cylindrical surface,and the turbulent entropy occurs in the wake region,where the dissipation rate is more significant.With the increase of the reduced velocity,the kinetic energy of water captured by the energy capture structure in the upper branch increases,the viscous entropy loss on the cylinder surface and the turbulent entropy production loss around the cylinder and in the wake region also increases,and the viscous entropy production loss on the surface of the energy capture structure increases.The increase of turbulent entropy production loss in the wake region is the main reason for the decrease in energy capture efficiency.