Aerodynamic lift

It is natural to expect anyone who claims to be a physicist to be able to give a simple, intuitive explanation of aerodynamic lift, using basic principles of classical mechanics.  Unfortunately, most of the time a physicist's such explanation is misleading, over-simplified, or just plain wrong.  One of the most important reasons for this is that there is no such simple, intuitive explanation.  I recently stumbled upon a reference to this excellent 2020 Scientific American article by Ed Regis, that outlines the two main competing explanations (Bernoulli's theorem vs. Newton's third law).  However, others such as the Coanda effect, have been proposed, and are not mentioned in the article.  Nonetheless Regis' article resonated with me because he seems to give a balanced discussion while debunking some of the clearly incorrect variants of these arguments.  He also spoke with two people whose insights I regard as essential, namely, John D. Anderson and Doug McLean.  Anderson is the author of a number of widely used textbooks on relevant topics, such as Introduction to Flight, Fundamentals of Aerodynamics, Modern Compressible Flow, Computational Fluid Dynamics: The Basics with Applications, and A History of Aerodynamics.  (I own three of these books.)  McLean is a retired Boeing engineer, and author of Understanding Aerodynamics, which I recently acquired.

I became interested in the competing intuitive explanations for aerodynamic lift during my time in graduate school, in the late 1990s.  At the time I was involved in atmospheric science research.  One of the professors I worked with informed the members of his lab that Prof. Anderson had been invited to visit our university; and moreover (knowing of my interest in this topic) my professor had invited Anderson to visit our lab for a discussion on it.  It was certainly an honor, and I and at least one other student in the group asked Prof. Anderson to sign our textbooks during his visit.  At the time, I was very partial to the Newton's third law version of the explanation (and still am, though I recognize it as woefully incomplete).  Anderson struck a more neutral tone, stating that both the Bernoulli principle and Newton's second law were at work in lifting an airfoil.  Neither of them was "wrong" per se.  That discussion over 20 years ago seems compatible with the views he gives in Regis' piece.

I won't discuss the officially accepted explanations, formulated in the early 20th century, given by Kutta and Zhukovsky, for 2-dimensional flow, and by Prandtl, Lanchester, and Prandtl's students (notably Blasius) for 3-dimensional flow, here.  However I note that Falkovich (Fluid Mechanics, 2/e, Cambridge University Press, 2018) points to the importance of viscosity in these formulations.  A purely inviscid flow "produces no lift" (p. 56).  He continues, "Without friction-caused separation [of the boundary layer], birds and planes would not be able to fly."  Neither the Bernoulli principle (which is strictly only true for inviscid flows) nor the Newton's third law explanation makes any reference to boundary layer separation and nonzero circulation around the airfoil.  As Anderson says in the Regis article, there just isn't a "one-liner" explanation of aerodynamic lift.