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Proceedings Paper

Velocity fields and optical turbulence near the boundary in a strongly convective laboratory flow
Author(s): Silvia Matt; Weilin Hou; Wesley Goode; Samuel Hellman
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Paper Abstract

Boundary layers around moving underwater vehicles or other platforms can be a limiting factor for optical communication. Turbulence in the boundary layer of a body moving through a stratified medium can lead to small variations in the index of refraction, which impede optical signals. As a first step towards investigating this boundary layer effect on underwater optics, we study the flow near the boundary in the Rayleigh-Bénard laboratory tank at the Naval Research Laboratory Stennis Space Center. The tank is set up to generate temperature-driven, i.e., convective turbulence, and allows control of the turbulence intensity. This controlled turbulence environment is complemented by computational fluid dynamics simulations to visualize and quantify multi-scale flow patterns. The boundary layer dynamics in the laboratory tank are quantified using a state-of-the-art Particle Image Velocimetry (PIV) system to examine the boundary layer velocities and turbulence parameters. The velocity fields and flow dynamics from the PIV are compared to the numerical model and show the model to accurately reproduce the velocity range and flow dynamics. The temperature variations and thus optical turbulence effects can then be inferred from the model temperature data. Optical turbulence is also visible in the raw data from the PIV system. The newly collected data are consistent with previously reported measurements from high-resolution Acoustic Doppler Velocimeter profilers (Nortek Vectrino), as well as fast thermistor probes and novel next-generation fiber-optics temperature sensors. This multi-level approach to studying optical turbulence near a boundary, combining in-situ measurements, optical techniques, and numerical simulations, can provide new insight and aid in mitigating turbulence impacts on underwater optical signal transmission.

Paper Details

Date Published: 17 May 2016
PDF: 11 pages
Proc. SPIE 9827, Ocean Sensing and Monitoring VIII, 98270F (17 May 2016); doi: 10.1117/12.2229800
Show Author Affiliations
Silvia Matt, U.S. Naval Research Lab. (United States)
Weilin Hou, U.S. Naval Research Lab. (United States)
Wesley Goode, U.S. Naval Research Lab. (United States)
Samuel Hellman, Dantec Dynamics Inc. (United States)

Published in SPIE Proceedings Vol. 9827:
Ocean Sensing and Monitoring VIII
Weilin W. Hou; Robert A. Arnone, Editor(s)

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