HR: 0800h
AN: OS51A-04    [Abstracts]
TI: Wakes of Maneuvering Bodies in Stratified Fluids
AU: * Voropayev, S I
EM: s.voropayev@asu.edu
AF: Arizona State University, Department of Mechanical and Aerospace Engineering, 1711 S Rural Rd., ISTB-2, Room 201C, Tempe, AZ 85287-6106, United States
AU: * Voropayev, S I
EM: s.voropayev@asu.edu
AF: Institute of Oceanology, Russian Academy of Sciences, Nakhimovskiy pr., 36, Moscopw, 117851, Russian Federation
AU: Fernando, H J
EM: j.fernando@asu.edu
AF: Arizona State University, Department of Mechanical and Aerospace Engineering, 1711 S Rural Rd., ISTB-2, Room 201C, Tempe, AZ 85287-6106, United States
AB: We present the results of experimental/theoretical studies on large momentum eddies generated in late wakes of unsteady moving self-propelled bodies in stratified fluids. The experiments were conducted with scaled submarine model at high Reynolds numbers (50,000), corresponding to the fully turbulent flow regime. Dye visualization and PIV were used for flow diagnostics. When a self-propelled body makes a maneuver, e.g. accelerates, it imparts net momentum on the surrounding fluid. We show that in a stratified fluid this leads to impulsive momentum wakes with large, long-lived coherent vortices in the late flows, which may be used as a signature for identification of submarine wakes in oceanic thermocline. First, we consider dynamics and properties of such wakes in a linearly stratified fluid and present a model that permits to predict the main flow characteristics. Second, we consider wakes in a two layer stratified fluid (analog of the upper ocean) and show that such wakes may penetrate to the water surface; we present a model for this phenomenon and propose criteria for the penetration of wake signatures to the water surface in terms of main governing parameters (signature contrast versus confinement number). Finally, we consider the evolution of such momentum wake eddies in the field of decaying background turbulence, which mimics the oceanic thermocline, and show that for the flow configuration studied the contrast number remains sufficiently large and detectable wake imprints survive for a long period of time. Some pertinent estimates for submarines cruising in the upper ocean are also given. For more details see [1-3]. This study was supported by grant from the Office of Naval Research. 1. Voropayev S.I., Fernando H.J.S., Smirnov S.A. & Morrison R.J. 2006. On surface signatures generated by submersed momentum sources. Phys. Fluids, under revision. 2. Voropayev S.I., Fernando H.J.S. & Morrison R.J. 2006. Dipolar eddies in a stratified turbulent flow. J. Fluid Mech., submitted. 3. Voropayev S.I., Smirnov S.A. & Fernando H.J.S. 2007. Late-wake vortices of maneuvering bodies in stratified fluids. J. Fluid Mech., submitted.
DE: 4528 Fronts and jets
DE: 4534 Hydrodynamic modeling
DE: 4568 Turbulence, diffusion, and mixing processes (4490)
DE: 4572 Upper ocean and mixed layer processes
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly