Measurements of Turbulence and Flow Structure in the Coastal Ocean using PIV

该项目继续我们的努力，测量流动结构和湍流底部10米的水柱的沿海海洋，并研究它们的依赖于海拔，环流，波场，底部地形和分层。湍流测量使用安装在伸缩式剖面平台上的潜水式粒子图像测速（PIV）系统进行，该平台具有10 m的剖面范围，可以在任何所需的方向上对齐样品区域。数据由两个独立样本区域的瞬时二维速度分布的时间序列组成。样本区域被间隔开，以获得雷诺应力与最小的波污染使用结构函数。通过不同的放大倍数，PIV数据可以分辨1.2 mm至1 m的长度尺度，从而可以直接计算耗散率。 激发本分析建议的部署的初步结果包括以下证据：a）雷诺应力和平均流随波相的变化。B）湍流产生率低于耗散率，以及底边界层外部应力随深度的变化。应力似乎与平均电流成比例。c）湍流能谱随着雷诺数的增加而增加与通用谱的相似性，但仍然表明所有尺度的各向异性，包括耗散范围。e）在中等但典型的潮汐流中，产生是间歇性的，发生在阵风期间，而耗散变化不大。正确的海洋环流模型对于改进气候、天气和人类对沿海海洋影响的预测是必不可少的。污染物、营养物和沉积物在沿海沃茨的迁移影响到沿海沿着人类生活的许多方面，包括经济、健康、旅游、渔业和粮食生产。必须获得知识和了解，从而改进对海洋迁移、环流和混合的预测。

This project continues our effort to measure the flow structure and turbulence in the bottom 10 m of the water column of the coastal ocean, and study their dependence on elevation, circulation, wave field, bottom topography and stratification. The turbulence measurements were performed using a submersible Particle Image Velocimetry (PIV) system mounted on a telescopic profiling platform with a 10 m profiling range that can align the sample area in any desired direction. The data consist of time series of instantaneous, 2-D velocity distributions in two independent sample areas. The sample areas are spaced to obtain the Reynolds stresses with minimal wave contamination using structure functions. With varying magnifications, the PIV data resolve length scales ranging between 1.2 mm to 1 m, enabling direct calculation of dissipation rate. Preliminary results from the deployments that motivate the present analysis proposal include evidence of: a) Variations of Reynolds stresses and mean current with wave phase. b) Turbulence production lower than the dissipation rate, and variations of stresses with depth in the outer portions of the bottom boundary layer. The stresses seem to scale with the mean current. c) Turbulent energy spectra that increase in similarity to the universal spectrum with increasing Reynolds number, but still indicate anisotropy at all scales, including the dissipation range. e) At moderate, but typical tidal flows, the production is intermittent, occurring during periods of gusts, while the dissipation changes little.Proper modeling of oceanic circulation is essential for improvements in predictions of climate, weather and human impact on the coastal ocean. Transport of pollutants, nutrients and sediment in coastal waters affect many aspects of human life along the coast including the economy, health, tourism, fisheries and food production. It is essential to obtain the knowledge and understanding that leads to development of improved prediction of oceanic transport, circulation and mixing.