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J. Mar. Sci. Eng. 2018, 6(2), 46; https://doi.org/10.3390/jmse6020046

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

1
Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061 USA
2
Department Head and Rolls-Royce Commonwealth Professor of Marine Propulsion, Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
*
Author to whom correspondence should be addressed.
Received: 1 March 2018 / Revised: 30 March 2018 / Accepted: 23 April 2018 / Published: 1 May 2018
(This article belongs to the Special Issue Marine Propulsors)
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Abstract

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 R e 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. View Full-Text
Keywords: actuator line; near wake; stratified; net-zero momentum; self-propelled; mixed patch; energy budget; axisymmetric actuator line; near wake; stratified; net-zero momentum; self-propelled; mixed patch; energy budget; axisymmetric
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Jones, M.C.; Paterson, E.G. Influence of Propulsion Type on the Stratified Near Wake of an Axisymmetric Self-Propelled Body. J. Mar. Sci. Eng. 2018, 6, 46.

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