基于频谱分析的水体波浪—紊动流速分离方法

根据波浪影响下水质点运动速度的频谱分布特征,本文提出了一种用于分离水体波浪轨道流速与紊动流速的分离方法.该方法仅需通过一台流速仪对水体瞬时流速进行高频测量,便可对水体波浪—紊动流速进行分离,实现受波浪影响水体的紊动分析.通过验证,频谱分析法不仅能够用于实验室中规则波浪条件下水体波浪—紊动流速的分离,还能够对野外不规则波条件下水质点运动速度进行分离.分离过程中,波浪窗口的频域设置可影响流速分离效果.当频域设置位于波浪窗口以外时,频域设置范围大小对分离结果影响较小,且均能对波浪—紊动流速进行有效分离.此外,流速测量频率对分离结果产生影响.当流速测量频率较低时,瞬时流速不能反映水体紊动信息,频谱分析法对流速的分离效果较差.

A method for wave-turbulent velocity decomposition based on spectral analysis

Based on the spectral characteristics of water motion velocity influenced by waves, this paper proposed a method for decomposing the wave orbital velocity and the turbulent velocity. With one velocimeter measuring flow velocity in high frequency, this method can decompose the wave and turbulent velocities from the instantaneous velocity and thus turbulent analysis can be made for water motion influenced by waves. According to the validations, the spectral method can be used in wave-turbulent velocity decomposition for not only the regular waves produced in the laboratory flume but also the irregular waves in the field. The results of decomposition were influenced by the frequency-domain settings. When frequency domains were set beyond the wave window, the wave and turbulent velocities could be well decomposed and the settings had less effect on the decomposition. Besides, the velocity sampling rate can also impact the decomposition. With a low sampling rate of velocity measurement, the instantaneous velocity cannot reflect the flow turbulence, leading to the wave and turbulent velocities cannot be decomposed accurately.