‘In offering to the public the first instalment of the present work, the author desires to record his conviction that the time is near when the study of Aerial Flight will take its place as one of the foremost of the applied sciences, one of which the underlying principles furnish some of the most beautiful and fascinating problems in the whole domain of practical dynamics.’
F. W. Lanchester — Preface to Aerodynamics (1907).

Frank Lanchester was born in 1863 and died in 1946. He lived through, and contributed significantly to, an astonishing expansion in aerodynamic knowledge and understanding. When he was a very small child, the Aeronautical Society of Great Britain was formed. Arguments about the underlying principles of aerodynamics were abundant, and manned powered flight was some 40 years into the future. When he died aerodynamics was well-established, codified and central to efficient aircraft design. Transonic flight through jet propulsion had almost been achieved.

Typical performance characteristics are presented for a cascade of two-dimensional bluff aerofoils employing circulation control from a tangential blowing jet. The cascade was tested in various configurations at a freestream Mach number of 0·3 and Reynolds number of approximately 1·5 x 105. Lift and drag coefficients and stream deflection are related to the blowing jet momentum coefficient. The expressions employed for lift and drag eliminate the direct effect of the blowing jet on measured performance, which was found to be influenced strongly by vortex shedding at low jet blowing rates.

For the configurations employed, tests showed that the economical application of circulation control on an uncambered blade could produce flow turning angles up to 20°.

The procedure described applies to aerofoils or cascades with circulation controlled by tangential blowing jets and provides a complete numerical solution for aerodynamic performance in incompressible flow conditions.

The pressure distribution over the blade surface is predicted by a potential flow model in which the region of separated flow is represented by an appropriated source distribution. Boundary layer development is calculated by a finite-difference solution of the parabolic boundary layer momentum equation: the development of the blowing jet and its mixing with the boundary layer over the curved trailing edge is predicted by the same procedure applied to an angular momentum equation, using an intermittency representation of the eddy viscosity distribution.

Predictions are compared with experimentally measured lift coefficients for an isolated aerofoil, with turning angles for a cascade tested by other workers and with experimental turning angles for a cascade tested by the authors. The agreement between theory and experiment is good.