Recent progress in the theory of air flow as applied to aeronautics

Prandtl, L
naca-tm-55
1922

In summing up it may be said that the hydrodynamic theories are best confirmed by experimental results for bodies with small resistance or drag and can accordingly be used in place of experimental tests.

An Adobe Acrobat (PDF) file of the entire report:
http://naca.central.cranfield.ac.uk/reports/1922/naca-tm-55.pdf