The University of Southampton
Engineering and the Environment

Research project: Numerical study of turbulent manoeuvering-body wakes

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This EPSRC-sponsored study is concerned with how the turbulent wake generated by a manoeuvering self-propelled body is affected by the different background environments found at various depths, well below and adjacent to the ocean surface.  We are interested in issues such as the underlying physics of the process by which the three-dimensional wake turbulence is converted into a single large, persistent 'dipolar vortex'.

Project Overview

In the past few decades, turbulent wakes behind a bluff body have been investigated both experimentally and numerically by many researchers in order to obtain better understanding of their dynamics.  However, almost all of the studies have focused on wakes behind towed or self-propelled objects moving at constant velocity.

In practice, a submerged vehicle (aircraft or submarine) often changes its speed or its direction.  During the period of unsteady motion, a significant net momentum is imparted to the wake leading to 'extra' dynamics that are absent from the constant-velocity case, especially where the wake is influenced by stable stratification or by the presence of an adjacent free surface.  For example, dipole vortices produced by the interaction of manoeuvering-body wakes with either stable background density stratification or a free surface can be observed in geophysical flows.  The practical importance of the dipole vortices is that they are very large, compared to the size of the body, and long-lived.  Estimates show that a coherent kilometre-scale vortical structure that persists for the order of days can be observed behind a typical submarine manoeuvre in the ocean.  Moreover, due to the self-propelling motion of the dipole vortex, it can transport mass, momentum and other scalar properties such as heat and salt.

The main approach of this study is to use Direct Numerical Simulation to investigate the manner in which a turbulent manoeuvring-body wake develops and interacts with its background.  Two distinct canonical flows are considered: manoeuvring-body wakes (1) in unbounded (both neutrally and stably stratified) quiescent conditions and (2) adjacent to a free surface.  The primary outcomes will be deeper insight into the physical mechanisms that control and affect these flows, and an assessment of how accurately their behaviour can be captured with simple models and scaling laws.

Some example simulations
Another example

Related research groups

Aerodynamics and Flight Mechanics

Staff

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