THE CALCULATION OF THERMOACOUSTIC OSCILLATIONS

Thermoacoustic oscillations occur in a wide variety of practical appli cations in which heat is supplied to an acoustic resonator. A simple g eometry is investigated systematically to determine the importance of various flow parameters on the frequency of the oscillations. Detailed consideration of elementary examples shows that the form of the coupl ing between the heat input and the unsteady flow has a crucial effect on the frequency of oscillation. The same elementary examples are used to compare how well (if at all) different calculation methods in the literature account for this influence. A mean flow and a distributed r egion of heat input significantly complicate the analysis of thermoaco ustic oscillations and are often neglected. Model problems are used to illustrate that mean flow effects can become significant even at mode st inlet Mach numbers, and to indicate circumstances under which a dis tributed heat input may be treated;as concentrated.