抄録
Pressure oscillation of fluid in a tube induces some temperature oscillation of the fluid. Radial distributions of the oscillating temperature are discussed from the viewpoint of thermoacoustic theory. The discussion is, for simplicity, restricted to the case that heat capacity of the tube wall is sufficiently large and temperature of the wall is homogeneous. For a gas far from the tube wall oscillation is expected to be isentropic and the temperature oscillation equal to Ts≡(ðT/ðp)sp, where p indicates pressure oscillation. For a gas contact to the tube wall, oscillation is isothermal and thus the temperature oscillation vanishes and entropy oscillation is ST≡(ðS/ðp)Tp. Therefore, oscillation temperature (T) is generally composed of two terms: T=Ts+Tp. The second term (Tp≡(ðT/ðS)pS) is isobaric temperature oscillation due to entropy oscillation (S). Since S=fαST for a gas in a tube of homogeneous temperature, oscillation temperature (T) is proportional to Ts such as T=(1-fα)TS. For a wide tube, fα can be approximated by exp(x/δα)exp(-ix/δα), where x indicates the distance from the surface of the tube, and thus |1-fα|2-1+|fα|2-2|fα|cos(x/δα). This expression shows that |1-fα| exceeds 1 at about twice the thermal boundary layer (δα) from the wall: oscillating amplitude of temperature can exceed that of isentropic oscillation.
