Numerical Investigation of Active Flow Control on Laminar Forced Convection over a Backward Facing Step Surrounded by Multiple Jets

Publish Year: 1400
نوع سند: مقاله ژورنالی
زبان: English
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شناسه ملی سند علمی:

JR_JAFM-14-2_009

تاریخ نمایه سازی: 15 دی 1400

Abstract:

Laminar, transient forced convection problem over a ۲D backward facing step (BFS) at an inlet Reynolds number (Re) of ۴۰۰ is investigated numerically using OpenFOAM. To increase the Nusselt number (Nu) along the bottom wall, active flow control is applied by zero-net-mass-flux (ZNMF) combinations of suction and injection through three thin slits which are placed on the top, step and the bottom walls in the vicinity of the BFS. The combinations of each jet velocity is determined by jet to inlet mean velocity ratios which are limited to integer numbers between -۲ and ۲ and satisfying ZNMF condition where negative and positive values indicate suction and injection, respectively. All ۱۹ cases which satisfy these rules are investigated. Average Nusselt number, friction coefficient and recirculation zone lengths are calculated along the bottom wall from time averaged flow fields. Among ۱۹ cases with each having different jet configuration, some cases converged to steady state solution while others indicated temporal effects and converged to periodic solutions. To understand these transient effects, velocity oscillation magnitude and Strouhal number which are monitored at a selected critical point are evaluated. It is shown that temporal interaction of chosen active flow control methodology has significant effect on enhancing mixing which results in an increase of Nusselt number. Among all cases, the best case concerning thermal improvement has an increase of ۷۸.۵% in Nu number while the best aerodynamic improvement is achieved for another case with a decrease of ۸۱% in total recirculation zone length compared to the reference case where no control is applied.

Authors

U. C. Coskun

Department of Mechanical Engineering, Istanbul Technical University (ITU), Istanbul, ۳۴۴۳۷, Turkey

S. Cadirci

Department of Mechanical Engineering, Istanbul Technical University (ITU), Istanbul, ۳۴۴۳۷, Turkey

H. Gunes

Department of Mechanical Engineering, Istanbul Technical University (ITU), Istanbul, ۳۴۴۳۷, Turkey