1937-01-01

Laminar and Turbulent Boundary Layers as Affecting Practical Aerodynamics 370178

THE main part of this paper deals with one of the unsolved problems that impede further progress - the aerodynamics of airfoil sections in relation to further research. In studying laminar and turbulent flow, special consideration is given to determining where the transition from one to the other takes place along the airfoil surface.
With no equipment capable of studying the subject experimentally in the higher full-scale range of Reynolds numbers, the problem has been attacked theoretically by two methods: According to the first method, the laminar boundary layer is supposed to become unstable.
With the second method of attack the mechanism of transition is supposed to be something like separation. This comparison has the advantage that the separation phenomenon is comparatively well understood and can be dealt with quantitively by means of existing theory. Separation and its relation to the transition phenomenon are therefore considered, and the actual behavior of the flow during its change from laminar to turbulent is illustrated.
The final conclusion reached, however, is that we do not know but should find out whether theoretical gains indicated are possible. Such investigation will require suitable equipment capable of reaching these very large Reynolds numbers.

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