Archives of Acoustics, 30, 1, pp. , 2005

Contemporary aspects of the theory and application of nonlinear acoustics

L. Björnö
UltraTech Holding

The foundations of nonlinear acoustics may be traced
nearly 250 years back in time, but only the last 50 years have shown an
increasing number of attempts to exploit the research results in nonlinear
acoustics. Based upon the fundamental equations of fluid dynamics, the
second-order acoustic equations may be derived which can be reduced to a
compound equation describing several of the most important and fast developing
areas of research in nonlinear acoustics. The relations between this compound
equation and Burgers' equation, Korteweg-DeVries equation, the K-Z-K equation,
Westervelt's equation and the general second-order wave equation are discussed
in depth. Finally, it is shown how the derivatives of the compound equation can
be applied to nonlinear acoustic research related to materials characterisation
by use of the B/A-ratio, to underwater acoustics by use of the parametric
acoustic array and to focused, high-power ultrasonic fields.
Keywords: nonlinear acoustics, absorption, diffraction, dispersion, focused fields, underwater applications, second-order nonlinearity parameter.
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