A Review of Blowing: as an Active Flow Control Strategy

Abstract

Flow control has significant technological importance as it can manipulate the flow field in a
desired way either actively or passively. This wide research area has remained the point of
attention for many years as it is applicable to various applications. Blowing as a flow control
method, among other methods, is more technically feasible and market ready technique. A
brief review from the existing literature on various studies on blowing has been presented
along with their outcome. Then, studies were conducted to investigate the performance
variation (in terms of lift coefficient, drag coefficient) of different airfoils with respect to
various blowing parameters. It was observed that for NACA 0012 airfoil the maximum lift
coefficient peaks at a blowing ratio 0.2 and then it decreases whereas the stalling angle
increases with rise of blowing ratio. For LA203A both maximum lift coefficient and stalling
angle increases with blowing ratio. For thick airfoil, it was found that lift increases with the
rise of moment coefficient and blowing ratio and mid chord slots gives better performance at
lower angles of attack whereas leading edge slots exhibits better performance at higher
angles of attack. In case of thick elliptical airfoil, increase in lift coefficient was noticed with
the increase in moment coefficient and blowing ratio but an optimum jet width to chord ratio
(0.41) was found beyond which increase in jet width causes drop in lift coefficient.
Additionally, it was found that at lower blowing angle thick elliptical airfoil performs better
compared to that of higher angles of attack. Study on NACA 0012 and Aerospatiale A proved
the fact that lifts increases with rise in blowing ratio at three different jet diameters to chord
ratios. This study also found that higher blowing ratio is also advantageous for the turbo
machinery in increasing the pressure difference. Lastly, the study on low Re airfoil flow
found that increasing blowing ratio has a deleterious effect on aerodynamics performance (in
terms of lift and drag coefficient).