Wake of a Self-Propelled Body, Part 2: Momentumless Wake with Swirl

Sirviente, A. I.; Patel, V. C.

doi:10.2514/2.1033

Cited by 15 publications

(5 citation statements)

References 6 publications

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“…For all three cases, KE r decays more rapidly than KE x and KE θ . The swirl component notably exhibits the slowest decay in the near wake, an observation consistent with Sirviente and Patel [9]. For the single-propeller case, this relative persistence leads to a rise in PE due to expansion of the wake and entrainment of the surrounding passive scalar T, indicating a change in density.…”

Section: Potential and Kinetic Energy Evolutionsupporting

confidence: 80%

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Influence of Propulsion Type on the Stratified Near Wake of an Axisymmetric Self-Propelled Body

Jones

Paterson

2018

JMSE

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To better understand the influence of swirl on the thermally-stratified near wake of a self-propelled axisymmetric vehicle, three propulsor schemes were considered: a single propeller, contra-rotating propellers (CRP), and a zero-swirl, uniform-velocity jet. The propellers were modeled using an Actuator-Line model in an unsteady Reynolds-Averaged Navier-Stokes simulation, where the Reynolds number is Re L = 3.1 × 10 8 using the freestream velocity and body length. The authors previously showed good comparison to experimental data with this approach. Visualization of vortical structures shows the helical paths of blade-tip vortices from the single propeller as well as the complicated vortical interaction between contra-rotating blades. Comparison of instantaneous and time-averaged fields shows that temporally stationary fields emerge by half of a body length downstream. Circumferentially-averaged axial velocity profiles show similarities between the single propeller and CRP in contrast to the jet configuration. Swirl velocity of the CRP, however, was attenuated in comparison to that of the single propeller case. Mixed-patch contour maps illustrate the unique temperature distribution of each configuration as a consequence of their respective swirl profiles. Finally, kinetic and potential energy is integrated along downstream axial planes to reveal key differences between the configurations. The CRP configuration creates less potential energy by reducing swirl that would otherwise persist in the near wake of a single-propeller wake.

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Section: Potential and Kinetic Energy Evolutionsupporting

confidence: 80%

“…In the near wake, these vortices break down, which is a topic of extensive study [8]. Although experiments show the contribution of swirl [9], its role in the evolution from near to far wake is not well-characterized.…”

Section: Introductionmentioning

confidence: 99%

Influence of Propulsion Type on the Stratified Near Wake of an Axisymmetric Self-Propelled Body

Jones

Paterson

2018

JMSE

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“…The velocity profile in figure 1(b) was observed experimentally for the mean velocity in the near wake by Naudascher (1965), Aleksenko & Kostomakha (1987), Higuchi & Kubota (1990) and Sirviente & Patel (2000a) in unstratified non-swirling axial jet-propelled momentumless wake studies, and for an unstratified swirling axial jet-propelled momentumless wake by Kostomakha & Lesnova (1995). The mirror image of figure 1(b) was obtained in momentumless cases with a propeller by Hyun & Patel (1991a,b) and Sirviente & Patel (2000b) for an offcentre swirling jet. It is important to note that in the presence of stratification, an initially momentumless wake will acquire a net momentum during its evolution due to the transfer of momentum from the wake to the background by internal waves.…”

Section: Introductionsupporting

confidence: 53%

“…For a propelled wake, the momentum source can take a number of forms including propellers, swirling jets, and non-swirling jets. Numerous experimental studies, mostly with an unstratified background, have shown that the wake behaves differently depending on the momentum source for a momentumless wake, see for example Schetz & Jakubowski (1975), Park & Cimbala (1991) and Sirviente & Patel (2000b, 2001. The presence of swirl is known to result in significant differences in both the net-momentum and momentumless cases; the effect is especially strong in the momentumless cases as noted by Chernykh, Demenkov & Kostomakha (2005) in their review of relevant literature.…”

Section: Introductionmentioning

confidence: 99%

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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“…Petersson et al [9] measured velocity unsteadiness in the ZFE and ZEF for water swirling jets downstream of a propeller and found their profiles to be similar to mean velocity profiles. Sirviente and Patel [16] compared the momentumless wake from a swirling air jet to that of a propeller. Although the near fields differed substantially, by 7D both jets reached the background velocity and both also exhibited a similar trend regarding turbulence production, i.e.…”

Section: Nearmentioning

confidence: 99%

Experimental study of the concentration field of discharge from a boat propeller

2010

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Engines in boats and ships using total loss lubrication deposit a significant proportion of their lubricant and fuel directly into the water. Their impact on the Australian coastline and marine ecosystems is of great concern. The purpose of this study was to document the velocity and concentration field characteristics of a submerged swirling water jet emanating from a propeller in order to provide information on its fundamental characteristics. The properties of the jet were examined far enough downstream to be relevant to the eventual modelling of the mixing problem. Measurements of the velocity and concentration field were performed in a turbulent jet generated by a model boat propeller (0.02 m diameter) within a 0.4 m-wide and 0.15 m-deep flume, operating at 1,500 and 3,000 rpm in a weak co-flow of 0.04 m/s. The measurements were carried out in the Zone of Established Flow up to 50 propeller diameters downstream of the propeller. Results pertaining to radial distribution, self-similarity, standard deviation growth, maximum value decay and integral fluxes of velocity and concentration fitted with empirical correlations. Furthermore, propeller-induced mixing and pollutant source concentration from a two-stroke engine were estimated.

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Wake of a Self-Propelled Body, Part 2: Momentumless Wake with Swirl

Cited by 15 publications

References 6 publications

Influence of Propulsion Type on the Stratified Near Wake of an Axisymmetric Self-Propelled Body

Influence of Propulsion Type on the Stratified Near Wake of an Axisymmetric Self-Propelled Body

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

Experimental study of the concentration field of discharge from a boat propeller

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