【摘要】 开展潮流的紊动特性研究,对于了解潮汐水域泥沙及污染物输运机理、保护生态环境具有重要意义。本文通过水槽试验系统全面地研究了潮位正弦变化的往复流紊动特性随潮变化规律,以100 Hz的高采样频率连续采集主流区测点三维瞬时流速,根据移动平均法及最小二乘原理计算时均流速过程曲线,据此分析了紊动强度及雷诺切应力随潮变化规律、特征潮时概率密度分布与正态分布的差异,以及脉动流速的紊动能谱。研究结果表明,水流纵向流速随潮近似于正弦规律变化;纵向、横向与垂向的相对紊动强度在转潮阶段出现峰值;涨急与落急时段,与纵向脉动流速相关的雷诺切应力相对较大,纵向与垂向脉动流速概率密度分布偏离正态分布;特征潮时的脉动能谱密度均随频率增大而减小,水流能量主要集中在10 Hz以内。更多还原

【Abstract】 Study on turbulent characteristics of tidal flow is essential to understand the mechanism of con-taminant and sediment transport,as well as ecological and environmental protection in tide water. A system-atic overall analysis was performed for the variation of turbulence in a tidal flow with sinusoidal water lev-el. Three-dimensional instantaneous velocity of a point in the mainstream region was sampled continuouslywith high sampling frequency of 100 Hz. The evolution of turbulent intensity and Reynolds shear stress,thedifference between measured probability density distribution and normal distribution at typical moments,aswell as turbulent energyspectrum of fluctuating velocity wereanalyzed,based on the mean velocity calculatedby a moving average method and principle of least squares. Results show that the longitudinal velocitychanges approximately in according to sinusoidal curve,the peak values of relative turbulent intensity in thelongitudinal,lateral,and vertical directions occur at the transitional stage of tides. Results also show thatfor flood tide and ebb tide,Reynolds shear stress associated with longitudinal turbulent velocity enhancesand the probability distribution of longitudinal and vertical fluctuating velocity deviates from the normal dis-tribution. It is also found that the density of turbulent energy spectra decreases with the increase of frequen-cy,and the main frequency is below 10 Hz for energy of water flow.更多还原