Flow Visualization and Mechanism of Underezpanded Sonic Jet Issuing from Straight Pipe

摘要

In this paper, the basic mechanism and characteristic of an underexpanded sonic jet issuing from a long straight pipe toward the atmosphere are investigated in detail. The experiments are carried out mainly for the mean Mach number, ranging from 0.4 to 1.6, at the pipe exit. In particular, as regards a pipe of inner diameter 6 mm, the flow visualization is conducted by the schlieren method, moreover the mean pressure and velocity distributions along the central axis and radial direction in jet are measured. The results measured are compared with the schlieren photographs and are discussed. As a result, the basic mechanism of pseudo-shock waves and the correlation between the static pressure and velocity distributions are clarified.