Upstream open loop control of the recirculation area downstream of a backward-facing step

Abstract

The flow downstream a backward-facing step is controlled using a pulsed jet placed upstream of the step edge. Experimental velocity fields are computed and used to the recirculation area quantify. The effects of jet amplitude, frequency and duty cycle on this recirculation area are investigated for two Reynolds numbers (Re h = 2070 and Re h = 2900). The results of this experimental study demonstrate that upstream actuation can be as efficient as actuation at the step edge when exciting the shear layer at its natural frequency. Moreover it is shown that it is possible to minimize both jet amplitude and duty cycle and still achieve optimal efficiency. With minimal amplitude and a duty-cycle as low as 10% the recirculation area is nearly canceled.

CFD Investigation of Flow Over a Backward-facing Step using an RNG k-? Turbulence Model

“…The recirculated and swirling flow occurs in many engineering applications well-presented by BFS geometry. This type of flow can be useful or harmful, depending on the application; examples include recirculation flow in electronic devices; recirculation flow in aerodynamics fields; flow around buildings in architectural applications; flow in combustion chambers; and the disadvantage of swirling flow at pipe bends (Mouza et al, 2005;Rouizi et al, 2009;Gautier & Aider, 2014;Ramšak, 2015;Saha & Nandi, 2017;Selimefendigil & Öztop 2017). There remain many turbulent flow phenomena over a BFS which are yet to be explored (Kasagi & Matsunaga 1995;Avancha, 2002).…”

“…A review of these geometry parameters was previously made by (Darmawan, 2016). Experimental method of flow over BFS geometry as done by (Kasagi & Matsunaga, 1995;Gautier & Aider, 2013) and many others involving advanced measurement techniques and recording facilities, which are very costly (Gautier & Aider 2014;Kasagi & Matsunaga 1995). Moreover, flexibility in varying the geometry design, lower cost, and faster and better visualization have made the CFD method more popular over the years, two dimensionally and three dimensionally (Thangam, 1991;Avancha & Pletcher, 2002;Nie & Armaly, 2002;Kanna & Das, 2006;Rouizi et al, 2009;Ramšak, 2015).…”

Non-Newtonian fluid flows through backward-facing steps

“…Among others, Louda et al [12] investigated the effect of 3D for the stationary conditions and they reported that these effects have a little importance. The flow through this geometrical configuration is known by its detachment behind the step [13]. The rotating flow backward the step increases the instabilities and interaction between the hot and cold mixed particles of fluid [14].…”