Regular Article

Streamwise and spanwise vortical structure merging inside the wake of an inclined flat plate

¹ Department of Fluid Dynamics, The Czech Academy of Sciences, Institute of Thermomechanics, Dolejškova 5, Prague 8 18200, Czech Republic
² Department of Power System Engineering, Faculty of Mechanical Engineering, University of West Bohemia, Universitní 8, Pilsen 30614, Czech Republic

^* e-mail: prochap@it.cas.cz

Received: 29 March 2019
Accepted: 3 November 2019

Abstract

The aim of this paper is to study the physics related to lift generation on an airfoil. A new hypothesis [1] of physical mechanism of flight relies on existence of streamwise vortical structures above the wing and inside the wake. The vortices origin as a consequence of flow instability inside the boundary layer developed under adverse pressure gradient. These structures are highly dynamical in nature, they change position and size very rapidly. A simple airfoil in the form of a flat plate with moderate angle of attack is considered in the presented research that generates suitable flow at rather low Reynolds number. Stereo PIV time resolved measurement technique is used to capture high-dynamic data in several planes which are located in the wake and are perpendicular to freestream or parallel to the airfoil. The overall image of the flow field dynamics will be created using POD decomposition. Distinct flow patterns with associated kinetic energy are to be described as well as their role in the studied case. Existence of streamwise vorticity is proved, topology and other parameters are estimated in the paper; however related pressures and forces are not evaluated.