): The wing generates a vortex-like flow that, when added to the free-stream flow, creates the lifting pressure distribution. This theorem states that lift ( ) is directly proportional to the circulation ( Γcap gamma ), density ( ), and velocity ( L=ρVΓcap L equals rho cap V cap gamma
) must decrease. This pressure difference creates a net upward force (lift).
-bernoulli's eqn relates pressure-velocity-density -it decreases as velocity increases
In an ideal fluid with zero viscosity (inviscid flow), air would simply wrap perfectly around a symmetrical object, resulting in zero net lift and zero net drag (D'Alembert's Paradox).
Drag decomposes into:
As McLean writes in the preface to his book: “The objective is to promote a solid physical understanding of aerodynamics. In general, any understanding of physical phenomena requires conceptual models”. The right conceptual models are the ones that accurately reflect real physics—not convenient oversimplifications.
While the principles above are foundational, a complete understanding requires quantitative data, experimental results, and vector calculus. A dedicated technical document, such as a provides:
When M ≳ 0.3 compressibility matters; at transonic and supersonic speeds new physics appear:
Caused by the shape of the object. High pressure builds up in front of a bulky object, while a turbulent, low-pressure wake develops behind it. The pressure imbalance pulls the object backward.
McLean’s central thesis revolves around the concept of "coupling." In incompressible flow, the pressure and velocity fields are inextricably linked. The "real physics" argument posits that the aerodynamic flow field is a solution to a global problem, governed by Newton’s laws and the continuity equation.
Turbulence is multiscale, chaotic fluctuation of velocity. From real-physics viewpoint: