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Evaluation of nonlinear constants from results of acoustic measurements. Regularization of problem

Leble S. B., Vereshchagin D. A., Vereshchagina I. S.

Hydroacoustics

2003

Vol. 6

159--166

The method of nonlinear constants B/A and C/A determination is discussed. It bases on comparison of experimental results of acoustic signal propagation with results of theoretical investigation of this problem. It is shown, that this problem, in general case, is ill-posed. So we use methods of ill-posed problem solution regularization. The values of the constants, which were extracted using this method, are in good accordance with estimations by other authors.

The estimation ot virial coefficients via the third harmonics measurements

Leble S. B., Zachariasz K., Vereshchagina I. S.

Hydroacoustics

1997

Vol. 1

83--88

The derivation of the next nonlinear term of the KZK equation is done within original perturbation scheme on the base of the virial expansion for thermic equation of state. We also derived equations for second and third harmonic components in the nearfield of the sound wave generated by a piston transducer. Calculation scheme for a numerical estimation of the integrals for the fundamental and second harmonics is proposed as well as for the averaged third harmonic component. Some results of performed calculations are given for the illustration of the method possibility and comparison with direct finite difference solutions of the KZK equation.

Generation conditions and nonlinear sound directed propagation in inhomogeneous medium

Perelomova A. A., Leble S. B.

Hydroacoustics

1997

Vol. 1

89--94

Boundary (and initial) conditions choice for the effective generation and propagation of nonlinear sound in a stratified medium is studied. The adjustment to a medium type is introduced via a choice of equations of state. Liquid, liquid with bubbles and gas cases are considered. Model propagation equations are derived for the special cases of plane directed waves. The application of the conditions in two-dimensional version (three-dimensional with the cylindric symmetry) is discussed and some test calculations of solutions are performed numerically. A good shape and direction conservation in a weak nonlinear conditions is discovered for a triangular initial wave from low frequency range.