Polivanov P.   Sidorenko A.  

Suppression of the separation zone by a spark discharge on laminar transonic airfoil

Reporter: Polivanov P.

Laminar transonic airfoil should allow to significantly improve the efficiency of aircraft of the next generation. Features of flow separation at the shock wave / laminar boundary layer interaction (SWBLI) are significantly different from the turbulent cases. For example in paper [1] it was found a significant difference between the frequency of laminar transonic buffet and turbulent one. This means that another ways of separation flow control can be used on laminar transonic airfoil. In paper [2] it was found that the minimum size of the zone of SWBLI is realized when the state of inflow boundary layer corresponds to the beginning of the laminar-turbulent transition (at small level of intermittency). Moreover the parameters of the zone of SWBLI at least are not improved for the fully turbulent case. Since the electrical discharge may introduce disturbances in the laminar boundary layer with a predetermined intermittency, it was decided to study the effect of plasma actuators on separated flows on laminar transonic airfoil.

The experiments were performed in wind tunnel T-325 (ITAM SB RAS) for Mach number M = 0.68-0.72, T0 = 290 K and P0 = 0.3-0.7E5 Pa. The following measuring methods were used: PIV, unsteady pressure sensors, high-speed Schlieren and IR visualization. Detailed measurements of stationary and unsteady characteristics of the separation zone were performed.

To control the separated flow a Multi Sliding Spark Discharge (MSSD) was used. The MSSD was installed in the middle part of the airfoil. In the experiment the parameters of the plasma actuator were chosen so that the activation of the discharge led to the rapid excitation of a turbulent spot in the laminar boundary layer. Possibility of the separation flow control and a significant decrease of the buffet pulsations by these actuators were demonstrated. The data obtained in the experiment made it possible to study the detail evolution of the separation zone at the crossing of a thermal and turbulent spot through it. This allowed to find the ways to improve the discharge effectiveness for this tasks.
The work was supported by Grant of President of the Russian Federation for State support of young Russian scientist – Candidates of sciences No Mk- 6682.2016.1 and grand RFBR No. 16-08-01134.

1. V. Brion, J. Dandois, S. Deck, L. Jacquin, P. Molton, Fulvio Sartor and D. Sipp. Transonic airfoil buffet: a decade of research at ONERA. XXIV ICTAM, 21-26 August 2016, Montreal, Canada.

2. P.A. Polivanov, A.A. Sidorenko, A.A. Maslov. Transition Effect on Shock Wave / Boundary Layer Interaction at M=1.47. AIAA Paper 2015-1974.

To reports list