Journal
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
Volume 30, Issue 5, Pages 877-885Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.ijheatfluidflow.2009.03.006
Keywords
Impinging jets; Pulsating jets; Time resolved PIV; Surface hot wires; Heat transfer enhancement
Categories
Funding
- German Ministry of Economics and Technology [10024592]
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The effects of jet pulsation on flow field and quasi wall shear stress of an impingement configuration were investigated experimentally. The excitation Strouhal number and amplitude were varied as the most influential parameters. A line-array with three submerged air jets, and a confining plate were used. The flow field analysis by means of time resolved particle image velocimetry shows that the controlled excitation can considerably affect the near-field flow of an impinging jet array. These effects are visualized as organization of the coherent flow structures. Augmentation of the Kelvin-Helmholtz vortices in the jet shear layer depends on the Strouhal number and pulsation magnitude and can be associated with pairing of small scale vortices in the jet. A total maximum of vortex strength was observed when exciting with Sr = 0.82 and coincident high amplitudes. Time resolved interaction between impinging vortices and impingement plate boundary layer due to jet excitation was verified by using an array of 5 mu m surface hot wires. Corresponding to the global flow field modification due to periodic jet pulsation, the impact of the vortex rings on the wall boundary layer is highly influenced by the above mentioned excitation parameters and reaches a maximum at Sr = 0.82. (C) 2009 Elsevier Inc. All rights reserved.
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