Lift in the aircraft
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In this coherent and clear explanation of the lift on the wing, the pressure is derived from the curvature of the streamlines and explains why the Kutta condition leads to a circulation at the tail edge, which ultimately provides the lift. The viscous flow is broken down into a boundary layer with friction and a frictionless potential flow outside the boundary layer. As the tail vortex separates from the sharp edge during takeoff, a circulation remains around the wing, which leads to a difference in speed above and below the wing. The Kutta-Joukowski formula can be used to calculate the lift force. The counterforce to the lift force in the sense of Newton's third law accelerates the air downwards and leads to vortices behind the wings. At the beginning it is explained why a common overly simplified explanation using only Bernoulli is not correct. Sources: Prof. Holger Babinsky, University of Cambridge https://www.cam.ac.uk/research/news/h... • Airflow across a wing L. Prandtl, Proceedings of the III. International Congress of Mathematicians, Heidelberg, 1904 see e.g.: https://www.univerlag.uni-goettingen.... Photo with vortices in the sky: iStock by Getty Images, Photo-ID 1125702735, The turbulence of the clouds left by the plane during the flight (Alextov) Simulations: The simulations displayed as the background show a potential flow outside the boundary layer. For the calculation, the Laplace equation for a velocity potential around an airfoil of the form Gö-387 was solved with Neumann boundary conditions on the surface. The local velocity and pressure were then calculated from the velocity potential and the movement of the air was represented dynamically. A difference method on a square grid was used for the calculation. As a result, the surface approximated by steps shows small numerical artifacts near the surface. For the images without tail vortex (with Kutta condition), the auxiliary plate at the end of the wing was hidden at the beginning of the video. The colors behind the tail edge are therefore only approximately correct in these images. 00:00 Introduction 01:24 curved streamlines 03:26 boundary layer 04:29 friction-free flow around 05:29 stagnation points 06:59 run times for flow around 07:51 tail vortex 09:01 Kutta condition 10:45 circulation and lift 13:14 force and counterforce 14:06 wake vortex
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