Acoustics - Propagation in a fluid

The wave propagation medium is assumed to be a perfect fluid. Viscosity, thermal conductivity and internal relaxation are neglected. As a result, entropy is conserved.

Then, the equations of motion and the equation of state of the fluid are linearized with respect to the characteristic quantities of the acoustic wave (mean velocity, acoustic pressure). Acoustic energy and energy flux are defined. The reflection and transmission coefficients of plane waves at the boundary of two fluids are expressed. This fluid-specific section (gas, liquid) concludes with an examination of nonlinear effects and the phenomena of attenuation and viscosity.

The "Acoustics" article is the subject of several booklets:

AF 3 810 General equations

AF 3 812 Propagation in a fluid

AF 3 814 Propagation in solids

The subjects are not independent of each other.

Readers will need to refer back to the other issues often enough.

In addition, you will find at the end of the booklet a table of the main notations used.