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An Experimental Study About Drag Crisis Phenomenon on Teardrop Model
摘要
Experiments were conducted in a wind tunnel with a teardrop model to investigate the phenomenon of drag crisis in a range of Reynolds numbers (Re) 2 x 10^4 ＜ Re ＜ 8 x 10^4. First of all, drag measurements were carried out to identify the Re range of the phenomenon at the angle of attack (AOA) = 0°. It was found that the drag coefficient was decreased from 0.43 to 0.15 through the transition range. Meanwhile, the velocity measurements made in the near wake region indicate that the wake width was narrowed substantially through this flow regime. Oil film results further evidenced the presence of laminar separation bubble (LSB) in the flow regime. Moreover, real-time pressure measurements on the model surface led to reduce a quantity called the intermittency factor which characterized the unsteady presence of LSB. The variations of the intermittency factor with respect to Re were found in good correlation with those of the drag coefficient measured. The characteristics of the drag crisis phenomenon under the non-zero AOA and roughness conditions were also investigated in this study.