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The Estimation of Laminar Skin Friction, including the Effects of Distributed Suction

Published online by Cambridge University Press:  07 June 2016

N. Curle
N. Curle*
Affiliation:
Aerodynamics Division, National Physical Laboratory
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Summary

Stratford's analysis of the laminar boundary layer near separation uses two physical ideas. In the outer part of the boundary layer, where viscous effects are small, the development is given by the condition that the total head is constant along streamlines, apart from a second-order correction for viscosity. Near the wall, however, viscous forces must balance the pressure forces, and the profile adjusts itself accordingly. Quantitatively these ideas yield a simple formula for predicting separation, which has been found to be particularly accurate.

In this paper it is indicated how the same approach may be used to yield the full distribution of skin friction along the wall. Further, the effects of suction may be incorporated into the method. Physically, suction affects the outer part of the boundary layer in that the streamlines are drawn towards the wall when suction is applied. At the wall, the balance between viscous and pressure forces is influenced by the momentum of the fluid which is sucked away. When these effects are accounted for quantitatively, the resulting formula for the skin friction is still very simple.

Several examples are considered, and comparison is made with exact theory and with approximate results by other methods. It is indicated that the method has a useful range of validity.

Type
Research Article
Information
Aeronautical Quarterly , Volume 11 , Issue 1 , February 1960 , pp. 1 - 21
Copyright
Copyright © Royal Aeronautical Society. 1960

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