Infrared Quantitative Imaging Velocimetry: Large Scale Instantaneous Velocity Measurements and Turbulence Metrics at the Surface of Rivers and Other Flows
Abstract
Accurate velocity measurements are critical for understanding physical, chemical, and biological processes in rivers and other waters, and their impact on ecosystems. However, velocimetry methods currently in use are limited in resolution, being able to measure either a high temporal resolution record at a single point (acoustic Doppler velocimetry, ADVs), or a mean velocity along a 1D transect (acoustic Doppler current profilers, ADCPs) or 2D area (e.g., radar; large-scale visible-light velocimetry, LSPIV). While LSPIV is capable of measuring over a large area, it depends on availability of lighting and passive tracers in the water, and is limited to mean velocity measurements.
Infrared Quantitative Imaging Velocimetry is a new, non-contact measurement method being developed by the authors, capable of measuring instantaneous velocity at the surface of rivers and other flows, with high spatial (centimeters) and temporal (several Hz) resolution, continuously and over a large area (hundreds of m^2), in almost all environmental conditions with no dependence on lighting or need for tracer particles. We describe the infrared image velocimetry system, including uncertainty considerations and fundamental differences from visible-light imaging velocitmetry, and present measurements made on large, tidally forced, rivers in California, USA, using this method. Motivated by fishery management questions, we characterize gradients in velocity near the channel sidewall, showing excellent agreement of our method and measurements made by ADCP and ADV over a period of several hours. Length scales of both the thermal field and the velocity field are used to estimate bathymetry, and hence estimate discharge from this single measurement. Our method is uniquely capable of measuring instantaneous velocity, and hence turbulence metrics, over a large area, introducing exciting applications in river and ecosystem management, e.g., correlating fish navigational choices with turbulence intensity in the flow, informing selective water withdrawal at bypasses and intakes to minimize impact on fish and other organisms, and more. We envision the deployment of this technology at multiple stations in river networks, greatly improving the understanding and expanding management options of these systems.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H31M2125S
- Keywords:
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- 0432 Contaminant and organic biogeochemistry;
- BIOGEOSCIENCESDE: 0481 Restoration;
- BIOGEOSCIENCESDE: 1830 Groundwater/surface water interaction;
- HYDROLOGYDE: 1871 Surface water quality;
- HYDROLOGY