Active control of flow around a square prism by slot jet injection

¹ Department of Mechanical Engineering, Çukurova University, TR 01330, Adana, Turkey
² Department of Mechanical Engineering, Niğde University, TR 01330 Niğde, Turkey

^a e-mail: efirat@cu.edu.tr
^b e-mail: akansu@nigde.edu.tr

Abstract

The main aim of the experimental study is to determine both the most effective injection surface and rate in order to ensure minimum drag and fluctuating forces on a square prism subjected to crossflow. All predetermined jet injection surfaces i.e. front, side, and rear, tested separately for injection ratios of IR = 0, 1, 1.5, 2 at Reynolds number of Re = 16,000. Surface pressures were measured by differential pressure transducer whereas instantaneous velocity measurements were performed by using multichannel Constant Temperature Anemometer (CTA). It was concluded that jet injection, especially from the rear surface, brought noticeable improvements to the flow characteristics of a square prism. For rear jet configuration with IR = 1.5, the mean drag coefficient ($\overline{C_{\text{DT}}}$) was reduced to 79.4% and C_{P RMS} level on side surfaces was reduced to 20% of that of the single square prism. In addition, instantaneous flow visualization photographs and Strouhal number (St) distribution across the injection ratio were also presented to identify the flow patterns and underlying mechanism of drag and fluctuating force reduction of square prism with rear jet configuration.