水平圆柱强迫振荡水动力特性的数值模拟

Numerical investigation of hydrodynamic characteristics on horizontal circular cylinder induced by a forced oscillatory

为了研究处于自由面以下完全淹没状态的水平圆柱在强迫振荡运动时的水动力特性,采用基于黏性流理论建立的二维两相流数值波浪水槽模型,对不同液相黏性条件下强迫振荡水平圆柱的受力进行计算,并对压力、黏性切力和圆柱运动之间的相位关系特征进行对比和分析,进而结合流场分析解释黏性影响机理。结果表明:黏性切力和涡旋压力对流体作用力的贡献差别是导致不同流体黏性下流体作用力结果差异的主要原因;涡旋运动相对圆柱振荡运动的滞后性受流体黏性影响显著,导致不同流体黏性下压力之间有相位差;流体水质点相对于圆柱的滞后运动在大黏性流体中更为显著,这导致了其黏性切力的相位超前现象。

This study investigates the hydrodynamic characteristics of a submerged horizontal circular cylinder under forced oscillation by using a 2-D two-phase flow numerical wave tank(NWT)model based on the viscous fluid theory.The calculations of the hydrodynamic forces on the circular cylinder under various liquid-phase viscosities were performed.By studying the relationship between the hydrodynamic forces and motion of the cylinder and analysing the flow fields around the cylinder,the mechanism of the viscous effects was identified.The study shows that differences between the results of the cases under different viscosities are on account of different contributions of the viscous shear forces to the total hydrodynamic forces and different influences of the vortex on the hydrodynamic forces.The considerable influences of fluid viscosity on the motion hysteresis of the vortex lead to a phase difference between the pressure forces on the cylinder under different viscosities.The phase advance phenomenon of the viscous shear forces can be explained by the fact that compared with the motion of the cylinder,the motion hysteresis of the water-particles in the higher viscosity fluid is more obvious.