Time-resolved measurements of total temperature and pressure in the vortex street behind a cylinder

Abstract

Recent theoretical and numerical investigations revealed the prospect that the instantaneous total temperature becomes separated around vortices; once time averaged, however, the wake behind a bluff body takes the guise of a colder wake, displaying the so-called Eckert–Weise effect. For low Mach number flows, the instantaneous total pressure was also shown to become separated in such a similar manner that the near-wake patterns of instantaneous total pressure exhibit almost exact facsimiles of those of total temperature. In this paper the results from the time-accurate measurements of fluctuating total temperature and pressure are presented. The data were obtained by placing a time-resolved aspirating probe in the vortex street behind a cylinder. The free-stream Mach number was 0.4 and the Reynolds number based on the cylinder diameter was 2.3×105. The maximum magnitude of the rms fluctuations of total temperature are of the order of 15 ° K—about 5% of the upstream total temperature. Maximum fluctuations in total pressure are approximately 10% of the upstream total pressure. Not only are the time traces of the total temperature and pressure taken in the near-wake qualitatively similar, but also quantitatively they agree with the predictions.