Taichi Yazaki

Experiments on thermally driven acoustic oscillations of gaseous helium

This paper describes experimental studies of thermally driven acoustic oscillations of a gas column (“Taconis vibration”) generated in a pipe whose end is closed at the warm part and open at the cold part. The stability curves and the frequency diagrams of the oscillations are experimentally determined under a given temperature distribution for the ratio of warm length of pipe to cold length as a parameter. The existence of two branches as predicted by Rotts theory is confirmed. A finite boundary layer thickness plays an important role in exciting and characterizing this type of instability.

Stability limit for thermally driven acoustic oscillation

Abstract The study of oscillatory instabilities occuring in cryogenic systems has a practical importance in the system development. One form of instability, thermally driven acoustic oscillation, is investigated experimentally using U-shaped tubes. The stability limit of oscillation for helium gas predicted by theory agrees well with our experimental results. The temperature ratio of a warm part to a cold one and the ratio of the inner radius of the tube to the Stokes boundary layer thickness are convenient variables for characterizing thermally driven acoustic oscillation.

Thermally driven acoustic oscillations: Second-harmonic☆

Abstract A second-harmonic is observed in a pipe closed at both ends with steep temperature gradients. The stability curves of the fundamental and the second-harmonic are experimentally determined, and the unstable region of the second-harmonic is estimated.

LOCAL THEORY OF THERMO-ACOUSTIC PHENOMENA: INVISCID CASF

Heat-flux, Q, and sound-source, W, due to acoustic wave are related to nonadiabatic oscillation of entropy, SN, for inviscid fluid. SN is estimated for a plane wave in a long cylindrical tube with a boundary condition that local oscillation of temperature is absent at the wall. Q and W obtained give Qualitative exnlanations of experiments.