Thermodynamic properties of fluid particles and energy fluxes in thermoacoustic oscillations

Abstract

Thermoacoustic Taconis oscillations of gaseous helium in a closed straight cylindrical tube are numerically studied. The tube is subject to a strong temperature gradient along the tube axis. The ratio of the temperature of the hot end parts to that of the cold center part is 15, and the length ratio of the hot part to that of the cold part is 1.0. The axisymmetric compressible Navier-Stokes equations are solved and fundamental antisymmetric mode of a standing wave is observed. Using the obtained flow field data, we trace fluid particles and their thermodynamic properties are calculated. The fluid particles oscillate and drift in the tube. In order to obtain a general picture of the energy conversion, the evolution of the distribution of the increase rate of heat is examined. It is shown that the rate is large in the region where the temperature gradient is large in the tube.