Three-dimensional visualization of stratified turbulent wakes at varying Reynolds number

Halawa, Basem; Merhi, S.; Tang, C.Y.; Zhou, Qi

doi:10.1007/s12650-020-00638-x

Cited by 8 publications

(5 citation statements)

References 29 publications

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“…It would be expected that the magnitude of any effects be greatly reduced due to the smaller gradient in properties. 7,21 The range of any effects would be expected to increase due to the lack of vertical motion suppression by a density gradient.…”

Section: Kangaroo Island Trialmentioning

confidence: 99%

Development of an experimental setup for measuring ocean property changes resulting from turbulence

G.S. Rugai,

Slimming,

Beniwal

et al. 2023

Ocean Sensing and Monitoring XV

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Traditional acoustic and magnetic techniques for detecting underwater vehicles are becoming less reliable due to advances in underwater technology such as composite materials, miniaturized electronics, and more space efficient battery technologies. Optical remote sensing technologies, such as Light Detection and Ranging (LiDAR) systems, are promising alternatives due to their high measurement accuracy, independence of operating environments, and simple integration onto airborne platforms. However, the penetration depth of direct detection methods is limited by the strong attenuation of light by the water column. Detection techniques that rely on monitoring changes to the inherent optical properties (IOPs) and other remotely sensed properties of water are thus being considered. Effects of underwater vehicles on ocean properties such as salinity and temperature have been well studied, but a stronger understanding of their effect on IOPs and optical constituents of the ocean is required for these new detection techniques. In this paper, the authors develop a system to measure the effect of underwater turbulence equivalent to an inspection-class Remotely Operated Vehicle (ROV) on the IOPs and other physical properties of the water column. Measurements are taken in an indoor water tank, freshwater reservoir, coastal waters and oceanic waters. Four vertical thrusters are used as a turbulence generator. Four commercially available sensors monitor the changes in IOPs and optical constituents of water above the turbulence generator. Preliminary results are presented on the effect of underwater turbulence on the optical and ocean properties measured. We conclude that the turbulence was able to be detected via changes in the IOPs at a distance of 10m under most conditions, with caveats and qualifiers discussed.

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Section: Kangaroo Island Trialmentioning

confidence: 99%

Development of an experimental setup for measuring ocean property changes resulting from turbulence

G.S. Rugai,

Slimming,

Beniwal

et al. 2023

Ocean Sensing and Monitoring XV

View full text Add to dashboard Cite

show abstract

“…Hence, these vortices are named "pancake vortices". 62 Experimental and numerical studies of the far wake have shown that highly-organised and long-lasting patches of vortex structures routinely form in the wake. 63 The vortex structures typically appear in the late stages of the turbulent wake evolution and are characterised by regions of oppositely-signed vortices organised in what is known as a Kármán vortex street.…”

Section: Turbulent Wakesmentioning

confidence: 99%

“…62 For a constant Froude number, the lifetime of the NEQ stage is longer for large Reynolds numbers, which causes the wake to persist for a longer period of time. 59,62,73,74 Furthermore, flows with higher Reynolds numbers have finer features within their pancake vortices. 59,62,63,73 Objects in a stratified medium (lower F r) produce wakes whose vertical motion is suppressed.…”

Section: Turbulent Wakesmentioning

confidence: 99%

“…59,62,73,74 Furthermore, flows with higher Reynolds numbers have finer features within their pancake vortices. 59,62,63,73 Objects in a stratified medium (lower F r) produce wakes whose vertical motion is suppressed. This has been verified by experiments 69 and numerical simulations.…”

Section: Turbulent Wakesmentioning

confidence: 99%

“…[70][71][72] Flows with large Reynolds numbers have wider turbulent wakes. 62 For a constant Froude number, the lifetime of the NEQ stage is longer for large Reynolds numbers, which causes the wake to persist for a longer period of time. 59,62,73,74 Furthermore, flows with higher Reynolds numbers have finer features within their pancake vortices.…”

Section: Turbulent Wakesmentioning

confidence: 99%

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The non-acoustic signatures of underwater vehicles

Slimming,

Beniwal,

Devrelis

et al. 2023

Ocean Sensing and Monitoring XV

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Submersible vehicles, such as Uncrewed Underwater Vehicles (UUVs), can be lost underwater and it is desirable to locate them before they go missing or collide with other vehicles. These objects generate inherent signatures when they move in the ocean. With a better understanding of these signatures, more information regarding the motion of underwater vehicles can be inferred using LiDAR technology. In this paper, the authors review existing literature on various non-acoustic signatures of a submerged body, namely, the electromagnetic, biological and thermal signatures, turbulent wake patterns, internal waves and vortex structures. The authors discuss how these signatures evolve both spatially and temporally. Furthermore, the review investigates how environmental and operational parameters such as the stratification of the medium, vehicle speed, shape and depth affect the non-acoustic signatures. Underwater vehicles operating at low speeds and large depths have bioluminescent, Kelvin wake and Bernoulli hump signatures that are difficult to detect on the surface. Thermal signatures, vortex wakes and far wakes are only likely to be detected at the vehicle’s depth. This is primarily due to the ocean stratification which suppresses the vertical motion of underwater turbulent signatures. Thermal signatures appear to be most likely to be detected. The study concludes that relying on a single signature to detect submersibles is not advisable and future methods for underwater vehicle detection should use multiple sensors to detect complementary signatures.

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Reduced-order representation of stratified wakes by proper orthogonal decomposition utilizing translational symmetry

Halawa

Zhou

2021

J Vis

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Three-dimensional visualization of stratified turbulent wakes at varying Reynolds number

Cited by 8 publications

References 29 publications

Development of an experimental setup for measuring ocean property changes resulting from turbulence

Development of an experimental setup for measuring ocean property changes resulting from turbulence

The non-acoustic signatures of underwater vehicles

Reduced-order representation of stratified wakes by proper orthogonal decomposition utilizing translational symmetry

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