Measurements of turbulent fluctuations of horizontal and vertical components of velocity, salinity and suspended particulate matter are presented. Turbulent Prandtl numbers are found to increase with stratification and to become larger than 1. Consequently, the vertical turbulent mass transport is suppressed by buoyancy forces, before the turbulent kinetic energy (TKE) and vertical turbulent momentum exchange are inhibited. With increasing stratification, the buoyancy fluxes do not cease, instead they become countergradient. We find that buoyantly driven motions play an active role in the transfer of mass. This is in agreement with trends derived from Monin–Obukhov scaling. For positive Richardson flux numbers (Ri _f ), the log velocity profile in the near-bed layer requires correction with a drag reduction. For negative Ri _f , the log velocity profile should be corrected with a drag increase, with increasing |Ri _f |. This highlights the active role played by buoyancy in momentum transfer and the production of TKE. However, the data do not appear to entirely follow Monin–Obukhov scaling. This is consistent with the notion that the turbulence field is not in equilibrium. The large stratification results in the decay of turbulence and countergradient buoyancy fluxes act to restore equilibrium in the energy budget. This implies that there is a finite adjustment timescale of the turbulence field to changes in velocity shear and density stratification. The energy transfers associated with the source and sink function of the buoyancy flux can be modeled with the concept of total turbulent energy.

中文翻译：

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关于总湍流能量以及浮力在湍流动量和传质中的被动和主动作用。

提出了测量速度，盐度和悬浮颗粒物的水平和垂直分量的湍流波动的方法。发现湍流Prandtl数随分层增加并大于1。因此，在抑制湍动能（TKE）和垂直湍动量交换之前，垂直湍流传质被浮力抑制。随着分层的增加，浮力通量不会停止，反而会变成反梯度。我们发现，由浮力驱动的运动在质量传递中起着积极的作用。这与从莫宁-奥布科夫规模发展所得出的趋势一致。对于正理查森通量数（Ri _f ），近床层的对数速度剖面需要通过减阻进行校正。对于负日_˚F，日志速度应当用拖拽的增加进行修正，随着|日_˚F |。这突出了浮力在动量传递和TKE生产中的积极作用。但是，数据似乎并不完全遵循莫宁-奥布科夫的标度。这与湍流场不平衡的观点是一致的。较大的分层导致湍流衰减，逆梯度浮力通量用于恢复能量收支平衡。这意味着湍流场的速度调整时间尺度是有限的，以适应速度切变和密度分层的变化。与浮力通量的源函数和汇函数相关的能量转移可以用总湍流能量的概念来建模。