Heat transfer characteristics in separated flows controlled by acoustic excitation

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Abstract

An experimental study has been conducted to investigate the heat/mass transfer and flow characteristics for flow over a backward-facing step and cavities with various aspect ratios. A naphthalene sublimation method is employed to measure the heat/mass transfer coefficients on the bottom wall. Acoustic excitations are forced on the separated flow using a woofer speaker placed above the step edge for Strouhal numbers between 0.2 and 0.4. In the spectra of streamwise velocity fluctuations for the flow excited at StH = 0.2, a sharp peak appears at the forcing frequency. For the backward-facing step, the reattachment length of about 6.7 H is reduced by 0.7 to approximately 1.5 H when the flow is forced by acoustic excitation. The peak Sh is located about 1.1 H upstream from the reattachment point. For the 10 H cavity, the reattachment of separated flow, which is unclear for a natural case, is produced clearly by the acoustic excitation. For the 5 H cavity, the turbulence intensity and heat/mass transfer coefficient in the recirculation region are slightly enhanced.

Original languageEnglish
Pages (from-to)653-658
Number of pages6
JournalJSME International Journal, Series B: Fluids and Thermal Engineering
Volume43
Issue number4
DOIs
Publication statusPublished - 2000 Nov

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering
  • Physical and Theoretical Chemistry
  • Fluid Flow and Transfer Processes

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