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 Jan 1

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acoustic excitation
separated flow
mass transfer
attachment
backward facing steps
Mass transfer
Acoustics
heat transfer
Heat transfer
heat
cavities
Strouhal number
Sublimation
flow characteristics
coefficients
Naphthalene
sublimation
naphthalene
upstream
aspect ratio

All Science Journal Classification (ASJC) codes

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

Cite this

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title = "Heat transfer characteristics in separated flows controlled by acoustic excitation",
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.",
author = "Kang, {Seung Goo} and Cho, {Hyung Hee} and Won-Gu Joo and Jinho Lee",
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TY - JOUR

T1 - Heat transfer characteristics in separated flows controlled by acoustic excitation

AU - Kang, Seung Goo

AU - Cho, Hyung Hee

AU - Joo, Won-Gu

AU - Lee, Jinho

PY - 2000/1/1

Y1 - 2000/1/1

N2 - 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.

AB - 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.

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