On the theory of thermodynamic wave cycles

Abstract

Cyclic thermodynamic processes governing the successive dissipation and formation of acoustic waves in perfect gases are studied under adiabatic flow conditions. The cyclic heat input into the fluid is due to the frictional conversion of the kinetic energy of the wave into heat. During the implementation of this dissipative heat addition, the pressure and temperature of the fluid increase and its density decreases. The elevated pressure at the end of the dissipative process causes and expansion, in which the pressure, temperature, and the density of the working medium all decrease, until the ambient pressure of the surroundings is reached. The fluid returns to its initial state by means of an isobaric cooling process, thus completing the wave cycle. The expansion process, in which the ambient pressure is reached determines the thermodynamic nature of the wave cycle; an isentropic expansion results in an isentropic wave cycle, similarly for an isothermal expansion, etc. Expressions for the mechanical work performed in various wave cycles are obtained and their efficiencies are discussed and related to the physics of dissipative wave motion.