科研之友
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摘要
An in-depth investigation of the Hartmann tube (HT) was carried out to gain a better understanding of and the effects of various parameters on its output flow characteristics. The HT used in this work consisted of an underexpanded jet directed into a close-ended cylindrical tube of the same diameter. The effects of tube depth, separation distance between the tube and the nozzle, and the jet Mach number were explored, Experiments were also performed on an HT fluidic actuator (HTFA). The HTFA operates under the same principles as the HT, except a major portion of the area between the nozzle and tube is shielded off, so that it can be used as a pulsating injector for flow control. Dynamic pressure measurements in the near field and microphone measurements in the far field provided temporal and spectral data. Instantaneous and phase-averaged images of the flow were obtained to explore the nature of turbulence structures within the flow. Limited hot-wire measurements were performed to characterize the velocity fluctuations at the exit of the HTFA. Striking similarities were observed in the frequency content and amplitude of tonal frequencies in near-field pressure and far-field acoustic measurements, as well as the flow results. Time traces of pressure in the tube were used to explain the major differences between the primary frequency of HT and the quarter-wave frequency. Flow visualization results showed a pulsating flow very rich in vortical structures. These images also revealed that the separation distance between the nozzle and the tube has a significant effect on the direction of the pulsating jet out of HT. The results illustrate many similarities, but also some differences between the HT and the HTFA.
- 出版日期2002-10
