HR: 14:35h
AN: OS43B-05 INVITED     [Abstracts]
TI: Nonlinear Analysis of Ocean Solitons and Their Effects on Ocean Acoustics
AU: * Chin-Bing, S A
EM: chinbing@nrlssc.navy.mil
AF: Naval Research Laboratory, 1005 Balch Blvd., Stennis Space Center, MS 39529-5004 United States
AU: Warn-Varnas, A C
EM: Alex.Warn-Varnas@nrlssc.navy.mil
AF: Naval Research Laboratory, 1005 Balch Blvd., Stennis Space Center, MS 39529-5004 United States
AU: Hawkins, J A
EM: jhawkins@psislidell.com
AF: Planning Systems, Inc., 115 Christian Lane, Slidell, LA 70458 United States
AB: Computer simulations by Zhou, Zhang, and Rogers [J. Acoust. Soc. Am. 90, 2042-2054 (1991)] have been used to demonstrate that a solitary wave packet (soliton) traveling in the ocean can dramatically effect an acoustic signal passing through the solitary wave. In their simulations they used a simple sinusoidal wave to represent the solitary wave packet. At certain acoustic frequencies their simulations showed a "resonance-like" loss in the acoustic signal that propagated through the sinusoidal wave. When this occurred they were able to show a connection between the spatial wave number of their sinusoidal wave and the adjacent acoustic wave numbers associated with acoustic mode conversions. The mode conversions occurred in the acoustic signal that propagated through the sinusoidal wave. Their computer simulation predictions of this resonance effect were in good agreement with their experimental measurements. Based on this good agreement they postulated that at certain acoustic frequencies the presence of shallow water solitary wave packets can result in acoustic mode conversions which consequently produce large signal losses. While this point of view has generally been accepted by the ocean acoustics research community, the equation that Zhou, et al., postulated as the connecting equation for this signal loss has not been generally accepted. The skepticism is justified. First, real acoustic data together with the necessary simultaneous oceanographic data is difficult to obtain, and consists of many complicating dynamics (fluctuations) other than pure solitary wave packets. Second, solitary wave packets in the ocean are nonlinear and are poorly approximated by sinusoidal waves. A better representation would have been given by nonlinear cnoidal functions. We discuss the limitations of using a linear Fourier representation for a realistic ocean soliton, and the advantages of using nonlinear cnoidal functions when attempting to apply the Zhou, et al., equation to understanding resonant acoustic signal losses. We demonstrate why their equation worked well for their analysis, and why it has not been as successful in analyzing resonances observed in other experiments. [Work supported by the Office of Naval Research with technical management by the Naval Research Laboratory.]
DE: 4259 Ocean acoustics
DE: 4263 Ocean prediction
DE: 4544 Internal and inertial waves
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly