The Response of Injection of Vortex Generator Jets to a Backward Facing Step Flow

2003 ◽  
Author(s):  
Koichi Yamagata ◽  
Manabu Saito ◽  
Tadashi Morioka ◽  
Shinji Honami
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Flow Behavior ◽  
Velocity Ratio ◽  
Vortex Generator ◽  
Step Response ◽  
Backward Facing Step ◽  
Longitudinal Vortices ◽  
Step Flow ◽  
Vortex Generator Jets

In this paper, the flow behavior of a reattachment process over a backward facing step flow is reported. The reattachment process is controlled by injection of vortex generator jets. The injection of jets upstream of the step produces the co-rotating longitudinal vortices in a separating shear layer. The experiment of the step response of the injection jet is also conducted in order to investigate the evolution process of the longitudinal vortices. A large scale of primary and counter vortices are observed, when the velocity ratio of the free stream to injected jet is 6. The detailed structure of the longitudinal vortices is clarified. The remarkable effect of the vortices on the separating shear layer downstream of the step is observed.

Active Control of a Backward Facing Step Flow With Plasma Actuators

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Juan D'Adamo ◽  
Roberto Sosa ◽  
Guillermo Artana
Keyword(s):  
Shear Layer ◽  
Active Control ◽  
Flow Behavior ◽  
Plasma Actuators ◽  
Backward Facing Step ◽  
Step Flow ◽  
Separated Shear Layer ◽  
Image Velocimetry ◽  
Layer Flow ◽  
Electrohydrodynamic Actuator

Active control over a backward facing step flow is studied experimentally by means of plasma based devices. The Reynolds number based on the step height h is 1520. An electrohydrodynamic actuator (EHD), dielectric barrier discharge (DBD) type, is flush mounted to the step wall. The DBD configuration adds momentum locally, normal to the separated shear layer, thus producing strong modifications downstream. The actuation is periodic and its frequency and amplitude are scrutinized to characterize the flow behavior under forcing. Measures of velocity fields for these flows are obtained from particle image velocimetry (PIV). As reported by previous works, the reattachment length shows an important reduction for an optimum forcing frequency. This value closely matches the shear layer flow natural frequency. On the other hand, the flow is less sensitive to the forcing amplitude though the analysis allows us to optimize the actuation in order to save power consumption.

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