The transition zone between the water column and the seabed is characterised by a considerable sediment transport due to the increasing concentration of sediments near the seabed. Bedload qualities also characterize this zone. While the second order nonlinear acoustic characteristics of sea water, described by the temperature dependent, dimensionsless ratio B/A, is lower than the nonlinear acoustical qualities of unconsolidated, water-saturated marine sediments (B/A=5.25 at 20 deg C for sea water and B/A=11 at 20 deg C for water-saturated fine sand) a considerable increase in acoustical nonlinearity is found across the transition zone. For applications of parametric acoustic arrays, utilising the nonlinear acoustical qualities of the medium for difference-frequency beamforming, it should be expected that the transition zone should contribute to an increased nonlinear conversion. However, the attenuation at the primary frequencies of the parametric array in the transition zone is increased, and a reduction of the nonlinear conversion is established. The interactions and the balance between the nonlinear acoustical and the attenuation effects are described by the Gol'dberg number. A comprehensive study of the Gol'dberg number as a function of concentration of sediments in suspension has been performed with emphasis on low-concentration suspensions. The consequences for the parametric acoustic conversion efficiency are discussed.
The Gol'dberg number of the seabed transition zone
Die Goldberg-Zahl der Meeresgrund-Übergangszone
Acustica ; 83 , 3 ; 467-472
1997
6 Seiten, 2 Bilder, 2 Tabellen, 23 Quellen
Aufsatz (Zeitschrift)
Englisch
SEABED PROJECTION IDENTIFICATION DEVICE AND SEABED PROJECTION IDENTIFICATION METHOD
Europäisches Patentamt | 2018
|Tema Archiv | 2000
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