The spatial and temporal structure of thermal fluctuations associated with a vertical turbulent jet impinging a water surface: laboratory experiments and field observations

摘要

Infrared imaging, in both laboratory and field settings, has become a vital tool in diagnosing near-surface thermalhydrodynamic phenomena such as convective cells, accumulation of surfactant, and coherent turbulent structures. In this presentation, we initially focus on a laboratory scale (0.01-1m) subsurface vertical turbulent water jet that serves as a canonical flow. The jet has a slightly elevated temperature thus the warmer fluid serves as a passive marker. Infrared image sequences of the surface thermal field were collected for various water jet flow rates and for both "clean" and surfactant-contaminated surface conditions. Turbulent characteristics of the near-surface flow field were measured by means of Digital Particle Image Velocimetry (DPIV), and these are used to examine the statistical nature of the coupled thermal-hydrodynamic field. An analog of the laboratory jet is the discharge of power-plant cooling water through a vertical pipe on the ocean floor. High-resolution airborne infrared imagery has recently been acquired of such a discharge (from the Huntington Beach Generating Station, CA), and these data are compared with the laboratory results in an attempt to understand striking spatial patterns discovered on the ocean surface.