NONLINEAR AND THERMOVISCOUS PHENOMENA IN ACOUSTICS .1.

The present paper is intended as a review (over 300 References) of som e basic concepts and modern investigations of nonlinear and thermovisc ous phenomena in acoustic fields in fluids. The focus is on theoretica l models of nonlinear acoustics for acoustic time-averages, sound beam s, and nonlinear standing waves. The well known topics of general use are considered and the facts which are essential to implementation are also given. Special attention is paid to the combined analysis of the effects of nonlinearity and absorption, to secondary processes in int ense sound fields, and to numerical simulation of nonlinear waves. The content includes: Section 1 Equations of state. Fluid state Section 2 Energy and momentum transfer in the sound field Section 3 Non-linear wave equation Section 4 Evolution equations and their solutions Sectio n 5 Standing waves The paper is published in three parts. Part I of th e paper includes sections 1 and 2. In section 1, nonlinear equations o f state for gases and liquids are reviewed. We also concern irreversib le processes accompanying pressure wave propagation. Section 2 present s the standard analysis of the acoustic time-averages in a non-absorbi ng fluid and its extension to absorbing medium. The properties and com parative energetics of acoustic streaming and acoustic heating are out lined. An interesting but probably very special effect of the self-ref lection of a nonlinear plane wave is further dealt with. Finally, we c onsider the important problem of the radiation force on small particle s.