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 () was reduced to 79.4% and CP 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.
Highlights
Square prism is the one of the most well-known shape in bluff body aerodynamics owing to the fixed separation points
For rear jet configuration with IR = 1.5, the mean drag coefficient ( ) was reduced to 79.4% and level on side surfaces was reduced to 20% of that of the single square prism
In order to reveal this, flow visualization was carried out just before and after the IR = 1.5. It is quite clear from the figure 7 that the vortex formation length was enlarged at the IR = 1.7. The physics of this event can be explained as follows: As the injection ratio reached to IR = 1.5, jet issuing from the slot on rear surface penetrated the recirculation region just behind the prism and prevented the movement of shear layers to opposite side of the horizontal centerline of square prism such like a splitter plate [14-17]
Summary
Square prism is the one of the most well-known shape in bluff body aerodynamics owing to the fixed separation points. It was intended to improve some aerodynamic characteristics (mean drag and fluctuating pressure coefficients) simultaneously, by controlling the flow around the square prism via active means. It was expressed that as plasma actuators were activated in pulsed mode, it was possible to reduce the drag and RMS lift coefficients by up to 32% and 72%, respectively. First step includes mean and fluctuating pressure measurement experiments for the determination of the most effective injection surface and rate for simultaneous drag reduction and VIV suppression. The latter step includes the further investigations about the underlying mechanism of the most effective jet configuration.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
