Analysis of Vortices Generation Process in Turbulent Boundary Subjected to Pressure Gradient

The paper is concerned with the experimental study of bursting process in turbulent boundary layer. For this purpose the novel identification process, developed by Drozdz and Elsner, J Phys: Conf Ser 318(6):062007, 2011, [3] based on VITA technique combined with quadrant analysis was applied. By the detection of four possible combinations of instantaneous gradients of u and v phase-averaged velocity traces this method allows to demonstrate such properties of vortices motion as: swirling direction, ascending or descending direction, the trajectory inclination. The analysis gives an evidence of four types of vortical structures present in the TBL which are responsible for the production of Q-type events, namely prograde and retrograde vortices, with the ascending and descending direction of motion. It was found that detected coherent structures have dominant share of the overall energy of velocity fluctuations.