Early Developments of Modern Aerodynamics: Incorrect!

· flying, theory of flight

We read in the opening chapter of Early Developments of Modern Aerodynamics by Ackroyd, Axcell and Ruban:

  • Our stress on viscosity will no doubt surprise newcomers to the subject. However, it must be emphasized at the outset that, without viscosity, all flight, even in nature, would be impossible since wings would produce no lift. From this it follows that both marine and aircraft propellers – essentially rotating wings – would be useless, while ships driven since antiquity by sails – flexible wings – would have suffered an extremely short history. Moreover, without viscosity we would all be in severe danger of asphyxiating in our own exhalations. Thus an understanding of the role of viscosity emerges as not only vital to any explanation of flight but also vital, quite literally, to life itself.

This is the central postulate of modern fluid mechanics attributed to the Prandtl as its Father: Lift and drag of a body moving through air or water, such as the wing of an airplane or sail/keel of a sailing boat, are effects of viscosity originating from a thin boundary layer.

We show that this is incorrect by computing solutions of the Navier-Stokes equations with a slip boundary condition, which do not exhibit any boundary layers yet have lift and drag in close accordance with observation. The central postulate of modern fluid dynamics is thus incorrect.

1 Comment

Comments RSS
  1. cessna Citation x

    May I just say what a relief to uncover a person that genuinely understands what they’re discussing on the net. You actually know how to bring an issue to light and make it important. A lot more people should look at this and understand this side of the story. I was surprised that you’re not more popular
    because you most certainly possess the gift.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: