Influence of the Angle of Attack of a Plate Located in the Turbulent Boundary Layer on Skin Friction

The author has presented results of numerical modeling of the influence of the angle of attack of a thin width-limited plate with a short chord on the velocity field of the internal region of a turbulent boundary layer (TBL) and skin friction. The computations were performed by the large eddy simulation (LES) method at the Reynolds number Re_θ = 540 calculated from the velocity on the channel axis and the momentum thickness. Changes in the average and pulsation characteristics of the three-dimensional velocity field under the impact of the wake of the plate and of tip vortices as functions of the angle of attack of the plate in the range ±1° have been analyzed. It has been shown that a determining influence on the formation of the velocity field is exerted by the tip vortices whose vorticity is opposite with the positive and negative angles of attack. The mean value of the skin-friction coefficient decreases by 6% at the positive angle of attack and by 14% at the negative angle with respect to the value of this coefficient in an unperturbed TBL.