Flow distortion around underwater gliders and impacts on sensor measurements: a pilot study using large-eddy simulations

Moat, B.I. ORCID: https://orcid.org/0000-0001-8676-7779; Smeed, D.A. ORCID: https://orcid.org/0000-0003-1740-1778; Marcinko, C.; Popinet, S.; Turnock, S.. 2016 Flow distortion around underwater gliders and impacts on sensor measurements: a pilot study using large-eddy simulations. Southampton, National Oceanography Centre, 35pp. (National Oceanography Centre Research and Consultancy Report, 58)

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Abstract/Summary

The suitability of computational fluid dynamics (CFD) to numerically simulate the flow of water over autonomous underwater vehicles (AUVs) was investigated. The aim was to examine the feasibility of using large-eddy simulation to investigate; 1) the extent to which the measurements of sensors (including turbulence sensors) on an AUV are affected by the distortion of the flow around the vehicle body, and 2) the quantification of the hydrodynamic forces on AUV’s. To this end the large-eddy simulation (LES) code Gerris was used to numerically simulate the flow around underwater gliders. Two example simulations were conducted. In both cases the flow around a Slocum Mk II glider was simulated and the second example included a MicroRider turbulence package mounted on top of the glider. The results of these studies illustrate the capability of CFD simulations but a more detailed study including further runs to examine the sensitivity of the results to model parameters and in some cases validation with experimental studies would be required before we could have full confidence in the results. The results suggest that CFD studies may have significant value in assessing the flow distortion around glider bodies and the resulting affects upon sensor measurements. Our preliminary results suggest that the usual position of the oxygen sensor on a Slocum glider may be within a separated wake that could significantly affect the data quality. Flow distortion at the location of the shear probes on the turbulence package is low but could result in a small underestimation of the magnitude of dissipation. Lift and drag forces diagnosed from the simulations were consistent with data from gliders but a more detailed study is needed to assess the quantitative accuracy of these results.

Item Type:	Publication - Report
Funders/Sponsors:	NERC
NORA Subject Terms:	Marine Sciences
Date made live:	28 Oct 2016 14:49 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/514980

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