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Study on turbulence characteristics and sensitivity of quadr
发布人:lyp    发布时间:2018-09-05 14:57    访问次数:

Abstract
The identification of coherent structures is very important in investigating the sediment transport mechanism and controlling the eutrophication in shallow lakes. This study analyzed the turbulence characteristics and the sensitivity of quadrant analysis to threshold level. Simultaneous in situ measurements of velocities and suspended sediment concentration (SSC) were conducted in Lake Taihu with acoustic Doppler velocimeter (ADV) and optical backscatter sensor (OBS) instruments. The results show that the increase in hole size makes the difference between dominant and non-dominant events more distinct. Wind velocity determines the frequency of occurrence of sweep and ejection events, which provide dominant contributions to the Reynolds stress. The increase of wind velocity enlarges the magnitude of coherent events but has little impact on the events frequency with the same hole size. The events occurring within short periods provide large contributions to the momentum flux. Transportation and diffusion of sediment are in control of the intermittent coherent events to a large extent.

Keywords:Turbulent burst; Sediment suspension ;Quadrant analysis ;Threshold level

摘要:研究分析了紊流特征和象限分析阈值的敏感性。结果表明,孔值的增大使主导事件与非主导事件之间的差异更明显。风速决定了喷射和清扫的出现频率,这两种事件对雷诺应力的贡献占主导。孔值相同时,拟序事件的量级随风速的增大而增大,但是对事件发生频率的影响很小。猝发事件出现频率小却对动量通量提供了很大的贡献。沉积物的传输与扩散很大程度上受到间歇性的拟序事件的影响。

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