Investigation of an impulsively started NACA0010 airfoil at Re = 5000 and at various angles of attack. Also investigation of a case with fast start and stop by Youri MARCHAL

This short seminar is focused on the (un)steadiness of the flow, as well as the aerodynamic behaviour, of an impulsively started NACA0010 airfoil at a Reynolds number of Re = 5000, and for 3 moderate angles of attack. The DNS results presented are obtained using the weak coupling method (developed by Philippe Billuart during his PhD thesis, and also modified for moving bodies during my Master thesis) between an Eulerian method (finite differences) and a Vortex Particle-Mesh (VPM) method. The development of the boundary layers and of their separation are investigated for the angles of attack considered. The unsteady circulation, lift and drag coefficients, are examined. The results are also usefully compared to the unsteady potential flow theory of Wagner (1925).
 
As an additional investigation, the airfoil subjected to a constant acceleration phase, followed by a constant velocity phase, and finally stopped using a constant deceleration phase, is also investigated. The initial goal of this simulation is to mimic an experiment that was carried in a water tank, and was aimed at creating an “ending vortex” with the deceleration phase, in addition to the “starting vortex” created during the acceleration phase, so that both vortices would then form a symmetric "two-vortex system". We will see that this is not very successful and we will explain why.

Image: Vorticity field for the case of the airfoil at 7 degree angle of attack.