Thermal performance of a logarithmic-spiral resonance tube

The simple Hartmann-Sprenger tube consists of a closed-end tube which is excited by an underexpanded gas jet facing its open end to produce violent, cyclic fluid oscillations internally and externally. The heat generation capability of this device has been exploited only relatively recently. The realization that thermal effects in the simple Hartmann-Sprenger tube resulted mainly from repeated shock heating of the fluid trapped inside led to the recognition that thermal performance could be enhanced either by strengthening the internal shock or increasing the frequency of the oscillations. The present investigation is concerned with the thermal performance of a Hartmann-Sprenger tube with a two-dimensional logarithmic spiral internal contour. A description is presented of experiments including thermocouple measurements. The results demonstrate that a Hartmann-Sprenger tube with a logarithmic spiral profile achieves a significantly greater base temperature than comparable tapered or rectangular tubes.