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The wall shear stress produced by the normal impingement of a jet on a flat surface

Published online by Cambridge University Press:  10 September 2000

DENIS J. PHARES
Affiliation:
Environmental Engineering Science Department, California Institute of Technology, Pasadena, CA 91125, USA Present address: Mechanical Engineering Department, University of Delaware, Newark, DE 19716, USA.
GREGORY T. SMEDLEY
Affiliation:
Environmental Engineering Science Department, California Institute of Technology, Pasadena, CA 91125, USA
RICHARD C. FLAGAN
Affiliation:
Chemical Engineering Department, California Institute of Technology, Pasadena, CA 91125, USA

Abstract

A method for the theoretical determination of the wall shear stress under impinging jets of various configurations is presented. Axisymmetric and two-dimensional incompressible jets of a wide range of Reynolds numbers and jet heights are considered. Theoretical predictions from this approach are compared with available wall shear stress measurements. These data are critically evaluated based on the method of measurement and its applicability to the boundary layer under consideration. It was found that impingement-region wall shear stress measurements using the electrochemical method in submerged impinging liquid jets provide the greatest accuracy of any indirect method. A unique wall shear stress measurement technique, based on observing the removal of monosized spheres from well-characterized surfaces, was used to confirm the impinging jet analysis presented for gas jets. The technique was also used to determine an empirical relation describing the rise in wall shear stress due to compressibility effects in impinging high-velocity jets.

Type
Research Article
Copyright
© 2000 Cambridge University Press

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