耦合四圆柱涡激振动的力特性及水动能获取分析

Force characteristics and hydrokinetic energy harvesting for VIV of four coupling-linked cylinders

涡激振动是一种常见的流固耦合现象,结构物振幅较大时,可利用涡激振动从海洋流中或河流中获取能量。通过流固双向耦合数值方法,模拟均匀来流下,弹性支撑刚性连接的耦合四圆柱在不同横向和流向间距比下的横向涡激振动。分析横向和流向间距比对该耦合结构涡激振动时的压力和升力特性及获取能量和能量密度的影响。结果表明:各种组合间距比下,上端两圆柱的升力系数均值CL与下端两圆柱的CL关于CL=0对称,压力系数幅值Ap关于θ=180°对称,但其升力系数均方根值却近似相等;获取的水动能及能量密度随着组合间距比的增加先增加,随后获取能量增加缓慢,而能量密度却不断减少,因此选择合理的横向和流向间距比可从单位水体的海洋流或河流中获取更多的水动能。

Vortex-induced vibration （VIV）is a common phenomenon of fluid-structure interaction.When VIV of a structure in water is larger,it can be used to extract energy from ocean or river currents.Here,a numerical method using two-way coupling between fluid and structure was presented to simulate VIV of four coupling-linked and spring-mounted cylinders in uniform currents.Different stream-wise and transverse spacing ratios were applied in simulation to identify their influence on not only lift and pressure characteristics but also energy harvesting and power density.The results revealed that the mean lift force coefficient CL of upper two cylinders and that of lower two cylinders are symmetrical about CL =0,the amplitudes of pressure coefficients are also symmetrical about θ=180°under various combinations of spacing ratios;the root mean square of lift force coefficient of upper two cylinders is approximately equal to that of lower two cylinders;the energy harvesting and power density increase with increase in spacing ratios firstly,then the energy harvesting increases slowly while the power density decreases;so reasonable stream-wise and transverse spacing ratios should be chosen to extract more hydrokinetic energy from water currents.