Simulating turbulence measurements in high flow ocean regions with an acoustic backscatter model

Shouldice, Emma (2019) Simulating turbulence measurements in high flow ocean regions with an acoustic backscatter model. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (14MB)

Abstract

Measurements of ocean turbulence are essential in understanding ocean mixing and bottom stress. These measurements of turbulence are also needed when es- tablishing loading forces on marine structures especially where they are deployed in regions of high turbulence. In particular, there is a need for accurate measurements of turbulence in regions where in-stream tidal turbines are being deployed. This study reports on two broadband Doppler sonar systems, the 1 MHz Signature Nortek AD2CP and the Workhorse 600 kHZ ADCP. The ability of these devices to collect accurate velocity measurements in tidal regions has been tested in the field (McMillan et al., 2016; Shcherbina et al., 2018); however we lack a way to directly validate the accuracy of these field measurements. This difficulty is addressed through the use of a three-dimensional numerical model of acoustic backscatter (Zedel, 2008, 2015). De- velopments to the model were completed for the present turbulence study, including the integration of data from a computational fluid dynamics simulation and an up- grade to the signal processing technique. The model can be used to simulate Doppler Sonar measurements in flows similar to those observed in regions where in-stream tidal turbines are deployed. The resulting model simulations show that turbulent structure can be resolved by both broadband Doppler systems, but that the 1 MHz Nortek AD2CP, which has a faster sampling rate, yields higher resolution results. This thesis discusses the uncertainty of the simulated results using quantitative tools and draws comparisons to an experimental study published by McMillan et al. (2016).

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