Dynamics of turbulent wake with small excess momentum in stratified media

Черных, Г. Г.; Moshkin, N. P.; Fomina, A. V.

doi:10.1016/j.cnsns.2008.01.014

Cited by 9 publications

(4 citation statements)

References 18 publications

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“…Higuchi & Kubota (1990) considered the case of a propelled wake with moderate excess momentum in an unstratified fluid and considered the case of a propelled wake with a small amount of excess momentum in a stratified fluid. Numerical work for the unstratified case was performed using a Reynolds-averaged Navier-Stokes (RANS) model by Lewellen, Teske & Donaldson (1974) and Chernykh, Moshkin & Fomina (2009) and with DNS by de Stadler & Sarkar (2011a) in a companion study to the present one. The only numerical work on the stratified case has been done using RANS by Chernykh et al (2009).…”

Section: Introductionmentioning

confidence: 99%

“…Numerical work for the unstratified case was performed using a Reynolds-averaged Navier-Stokes (RANS) model by Lewellen, Teske & Donaldson (1974) and Chernykh, Moshkin & Fomina (2009) and with DNS by de Stadler & Sarkar (2011a) in a companion study to the present one. The only numerical work on the stratified case has been done using RANS by Chernykh et al (2009). Tennekes & Lumley (1972) consider what happens when a momentumless selfpropelled wake is contaminated by a small amount of excess momentum in an unstratified fluid.…”

Section: Introductionmentioning

confidence: 99%

“…Numerical work for the case of a stratified, self-propelled wake with excess momentum is limited to Chernykh et al (2009), who employ a modified k-ε turbulence model for their RANS simulations. Chernykh et al (2009) found that a small amount of excess momentum has a significant effect on the defect velocity but a small impact on turbulent kinetic energy and internal wave radiation. Note that their solution technique used symmetry arguments to solve the flow in one quadrant of the domain.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of a propelled wake with moderate excess momentum in a stratified fluid

Stadler

Sarkar

2011

J. Fluid Mech.

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Direct numerical simulation is used to simulate the turbulent wake behind an accelerating axisymmetric self-propelled body in a stratified fluid. Acceleration is modelled by adding a velocity profile corresponding to net thrust to a self-propelled velocity profile resulting in a wake with excess momentum. The effect of a small to moderate amount of excess momentum on the initially momentumless self-propelled wake is investigated to evaluate if the addition of excess momentum leads to a large qualitative change in wake dynamics. Both the amount and shape of excess momentum are varied. Increasing the amount of excess momentum and/or decreasing the radial extent of excess momentum was found to increase the defect velocity, mean kinetic energy, shear in the velocity gradient and the wake width. The increased shear in the mean profile resulted in increased production of turbulent kinetic energy leading to an increase in turbulent kinetic energy and its dissipation. Slightly larger vorticity structures were observed in the late wake with excess momentum although the differences between vorticity structures in the self-propelled and 40 % excess momentum cases was significantly smaller than suggested by previous experiments. Buoyancy was found to preserve the doubly inflected velocity profile in the vertical direction, and similarity for the mean velocity and turbulent kinetic energy was found to occur in both horizontal and vertical directions. While quantitative differences were observed between cases with and without excess momentum, qualitatively similar evolution was found to occur.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulation of a propelled wake with moderate excess momentum in a stratified fluid

Stadler

Sarkar

2011

J. Fluid Mech.

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“…The imaging characteristics and detection of a far-field turbulent wake have been studied extensively [6][7][8], but little research has been conducted on the near-field turbulent wake. In a previous study, a numerical model of turbulence with small momentum was built, and the relationship between the excess momentum and flow characteristics of a turbulent wake was studied [9,10]. Wang et al [11] researched the turbulence generated by the propellers of underwater targets.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic Scattering of Near-Field Turbulent Wake Generated by Accelerated Propeller

et al. 2021

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The electromagnetic scattering study of the turbulent wake of a moving ship has important application value in target recognition and tracking. However, to date, there has been insufficient research into the electromagnetic characteristics of near-field propeller turbulence. This study presents a new procedure for evaluating the electromagnetic scattering coefficient and imaging characteristics of turbulent wakes in the near field. By controlling the different values of the net momenta, a turbulent wake was generated using the large-eddy simulation method. The results show that the net momentum transferred to the background flow field determines the development of the turbulent wake, which explains the formation mechanism of the turbulence. Combined with the turbulent energy attenuation spectrum, the electromagnetic scattering characteristics of the turbulent wake were calculated using the two-scale facet mode. Using this method, the impact of different parameters on the scattering coefficient and the electromagnetic image of the turbulence wake were investigated, to explain the modulation mechanism and electromagnetic imaging characteristics of the near-field turbulent wake. Moreover, an application for estimating a ship’s heading is proposed based on the electromagnetic imaging characteristics of the turbulent wake.

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The age of a wake

Radko

Lewis

2019

Physics of Fluids

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This study attempts to quantify the decay rates of stratified wakes in active oceanic environments, characterized by the presence of intermittent turbulence and double-diffusive convection. Of particular interest is the possibility of utilizing standard oceanographic microstructure measurements as a means of wake identification and analysis. The investigation is based on a series of direct numerical simulations of wakes produced by a sphere uniformly propagating in stratified two-component fluids. We examine and compare the evolution of wakes in fluid systems that are (i) initially quiescent, (ii) double-diffusively unstable, and (iii) contain preexisting turbulence. The model diagnostics are focused primarily on the dissipation of turbulent kinetic energy (ε) and thermal variance (χ). The analysis of decay patterns of ε and χ indicates that microstructure generated by an object of D = 0.6 m in diameter moving at the speed of U = 0.02 m/s could be detected, using modern high-resolution profiling instruments, for 0.5–0.7 h. The detection period depends on environmental conditions; convective overturns are shown to be particularly effective in terms of dispersion of microscale wake signatures. The extrapolation of model results to objects of ∼10 m in diameter propagating with speeds of ∼10 m/s suggests that the microstructure-based wake detection is feasible for at least 4 h after the object’s passage through the monitored areas. The overall conclusion from our study is that the measurement of microscale signatures of turbulent wakes could represent a viable method for hydrodynamic detection of propagating submersibles.

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Dynamics of turbulent wake with small excess momentum in stratified media

Cited by 9 publications

References 18 publications

Simulation of a propelled wake with moderate excess momentum in a stratified fluid

Simulation of a propelled wake with moderate excess momentum in a stratified fluid

Electromagnetic Scattering of Near-Field Turbulent Wake Generated by Accelerated Propeller

The age of a wake

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