Plume outflow intrusion impact on acoustical signal fluctuations in a pre-stratified environment

Author

Assistant Professor, Faculty of Marine & Oceanic Science, University of Mazandaran, Babolsar, Iran

Abstract

Existence of outflow intrusion introduces small-scale turbulence that perturbs the vertically stratified character of the sound velocity and causes spatial and temporal fluctuations of the sound propagation. In this experimental study, we have investigated acoustic wave propagation with frequency of 50 kHz in a pre-stratified environment with intrusion of a turbulent plume while the signals received in different locations and times are recorded. At first, a fourth-order Butterworth band-pass filter was applied to the received voltage time series. Then the signals received at different times when entering the outflow intrusion at similar depths are compared to the ones without plume intrusion. In order to investigate the shapes of the signals received at different moments of the experiment they are analyzed in the time domain using trace envelope techniques. The results show that if the transmitter is positioned in the outflow intrusion location, the received signals in the upper and lower part of the outflow intrusion show a signal amplitude increase but the received signals in the dyed outflow show a signal amplitude decrease. Thereby, results indicate that the outflow intrusion could be important in shapes of the received signals. Also we have observed the occurrence of major signals fluctuations over time is accordance with the sound speed vertical structure changes due to the intrusion development.

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References

[1] L.M. Brekhovskikh, I.P. Lysanov, Fundamentals of ocean acoustics, Springer Science & Business Media, 2003.
[2] P.C. Etter, Underwater acoustic modeling and simulation, CRC Press, 2013.
[3] C.V.K. Prasada Rao, Modelling of coastal ocean environment for underwater surveillance, Indian Journal of Marine Sciences, 39 (2010) 616.
[4] K.N. Fedorov, The thermohaline finestructure of the ocean: Pergamon marine series, Elsevier, 2013.
[5] B.R. Ruddick, J.S. Turner, The vertical length scale of double-diffusive intrusions, Deep Sea Research Part A. Oceanographic Research Papers, 26 (1979) 903-913.
[6] A.C. Lavery, T. Ross, Acoustic scattering from double-diffusive microstructure, The Journal of the Acoustical Society of America, 122 (2007) 1449-1462.
[7] T. Ross, R. Lueck, Sound scattering from oceanic turbulence, Geophysical Research Letters, 30 (2003).
[8] H.E. Seim, M.C. Gregg, R.T. Miyamoto, Acoustic backscatter from turbulent microstructure, Journal of Atmospheric and Oceanic Technology, 12 (1995) 367-380.
[9] J.D. Warren, T.K. Stanton, P.H. Wiebe, H.E. Seim, Inference of biological and physical parameters in an internal wave using multiple-frequency, acoustic-scattering data, ICES Journal of Marine Science: Journal du Conseil, 60 (2003) 1033-1046.
[10] W.D. Baines, J.S. Turner, Turbulent buoyant convection from a source in a confined region, Journal of Fluid Mechanics, 37 (1969) 51-80.
[11] C.T. Chen, F.J. Millero, Speed of sound in seawater at high pressures, The Journal of the Acoustical Society of America, 62 (1977) 1129-1135.
[12] N.P. Fofonoff, R.C. Millard, Algorithms for computation of fundamental properties of seawater, (1983).
[13] A.B.D. Wong, R.W. Griffiths, G.O. Hughes, Shear layers driven by turbulent plumes, Journal of Fluid Mechanics, 434 (2001) 209-241.
[14] C.S. Clay, H. Medwin, Acoustical oceanography: principles and applications, John Wiley & Sons, 1977.
[15] P.K. Pullarao, Modeling and simulation of an underwater acoustic communication channel, in:  Department of Electrical Engineering and Computer Science, University of Applied Sciences, Bremen, Germany, 2004.
[16] M.T. Taner, F. Koehler, R.E. Sheriff, Complex seismic trace analysis, Geophysics, 44 (1979) 1041-1063.
[17] L. Cohen, Time-frequency analysis, Prentice hall, 1995.
[18] A.S. Bower, H.D. Hunt, J.F. Price, Character and dynamics of the Red Sea and Persian Gulf outflows, Journal of Geophysical Research, 105 (2000) 6387-6414.

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