Influence of unsteady wake on a turbulent separation bubble

Multi-resolution analysis of the large-scale coherent structure in a turbulent separation bubble affected by an unsteady wake

“…These unsteady events are significantly impacted by the introduction of an unsteady wake in the incoming flow. Chun and Sung (2002) systematically studied the separated and reattaching flow under the influence of unsteady wakes with variable frequencies and rotation directions. Compared with the reattachment length of the separated flow of x R ¼ 7.0 obtained at St H ¼ 0, the reattachment lengths in the presence of a CW or CCW rotating unsteady wake were optimally reduced to x R ¼ 4.0 and 2.4, respectively, for St H ¼ 0.2.…”

“…The shapes of the curves in the frequency domain at D 2 -D 7 are similar. The most energetic largescale vortices are buried in D 7 , as determined from the previous observation that the vortex shedding frequency is St ¼ 0.09 for this system (Chun and Sung, 2002). S 7 contains the major components of the flapping frequency at St ¼ 0.02.…”

“…In this study, large-scale turbulent structures were analyzed using multi-resolution analysis (MRA), and the flow configuration was the same as that of Chun and Sung (2002). Two wake-passing frequencies (St H ¼ 0 and 0.2) were chosen for comparison.…”

“…Two wake-passing frequencies (St H ¼ 0 and 0.2) were chosen for comparison. The wake generator was rotated in either a clockwise (CW) or counter-clockwise (CCW) direction, yielding entirely different flow structures (Chun and Sung, 2002). Measurements of wall-pressure and velocity fluctuations were simultaneously conducted using a microphone array and a hot-wire anemometer, respectively.…”

Studies on Effects of Periodic Wake Passing upon a Blade Leading Edge Separation Bubble (Suppresion of Separation Bubble Due to Wake Passing)

“…Funazaki and Kato (8) , using a simple scaled leading edge model of a compressor blade and the moving bar mechanism, executed detailed measurements of the separated boundary layer on the test model affected by the periodic wake passing. Similarly, a simplified flat-plate model experiment was made by Ottavy et al (9) , followed by Chun and Sung (10) . The present study is an extended version of the previous study by Funazaki and Kato (8) using almost the same test facility, aiming at the clarification about how and to what extent the periodic wake passing suppresses the leading edge separation bubble occurring near the leading edge of the test model under various flow conditions, such as wake-passing Strouhal number, inlet Reynolds number and incident of the model.…”