Phase averaged Reynolds stresses, flow actuated at St=0.2

Phase averaged velocities, flow actuated at St=0.2

Fig.1 ​Topology of the BFS flow actuated at St=0.2

Active flow control of a separating turbulent boundary layer using a synthetic jet actuator 

Abstract


In this first part of the project, we aimed to look at the induced separating turbulent boundary layer in a backward facing step flow configuration. An active flow control strategy was adopted using a synthetic jet actuator.  In order to look at the dynamical behavior of the flow in such condition, a first characterization of the SJA was achieved. Using thermal anemometry, the SJA has shows a linear to frequency response, and reaching an output velocity of 30m/s.  


An experimental investigation was carried out, by phase-locking the PIV to the SJA's response, and random PIV for a reference case. The SJA effect has shown to have large scale modification  in the flow topology for different actuation, ranging to a one order of magnitude from the initial case. The effective impact of the SJA is shown by a large reduction of the averaged reattachment point for the lowest actuation frequency by nearly 30%, whereas an increase of the reattachment by 15%. these cases demonstrate however two opposite trends regarding the viscous and pressure grad. Where using a pressure estimation from PIV data, we notice that the SJA performs well regarding the pressure recovery at high frequency actuation, whereas at lower frequency the pressure fluctuationas are much more pronounced  



Project leader : Takfarinas Medjnoun

Main supervisor(s): Prof. Ganapathisubramani