Active control of impinging jet for modification of mixing

作者：Kim Jungwoo^*

来源：Journal of Mechanical Science and Technology, 2014, 28(3): 927-935.

DOI：10.1007/s12206-013-1160-1

• Heat transfer rate
• Impinging jet
• Mixing
• Single-frequency excitation
• Vortical structures

The objective of the present study is to modify mixing and heat transfer in impinging jets using a single-frequency excitation imposed at the jet exit. The excitation frequency is selected to be St (theta) = f theta/U (J,max) = 0.017 where theta is the jet-exit momentum thickness and U (J,max) is the jet-exit maximum velocity. In free jets, this excitation results in turbulence suppression in a downstream location. On the other hand, in impinging jets, the effect of excitation significantly depends on the distance (H) between the jet exit and the impinging wall. For large H (e.g. H / D = 10, D is the jet exit diameter), the Nusselt number near the stagnation point (Nu (stag) ) decreases due to turbulence suppression by the excitation. For small H (e.g. H / D = 2), Nu (stag) is almost unchanged but the secondary peak much suppressed. On the other hand, Nu (stag) increases for H / D = 6 due to turbulence enhancement by the excitation. The different behaviors of Nusselt number with respect to H / D are closely related to the changes in vortical structures by excitation.

• 出版日期2014-3