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|Title:||The measurement of wall shearing stress in turbulent boundary layers.|
|Authors:||Miller, B. L. P.|
|Presented at:||University of Leicester|
|Abstract:||The thesis describes the design, calibration and use of a floating element skin friction meter in smooth wall boundary layers under favourable and adverse pressure gradients. The results of an experimental investigation in turbulent, fully developed duct flow are combined with those obtained by BROWN and JOUBERT (1) to give a secondary force contour map for element Reynold's numbers (dm ur/v) between 500 and 4000 and element Euler numbers between -16 and +20. It is shown that these meters can be used in favourable pressure gradient rough wall flows and that the secondary force characteristics are similar to those obtained over smooth walls. Simple physical and mathematical models for the secondary forces are developed which show good qualitative agreement with experiment. A strongly non-equilibrium boundary layer (-1.2 > delta*/tw dp/dx > 2.6) is investigated in detail and tabulated results given. A modified form of COLE'S (4) method for establishing the skin friction coefficient (Cf) from the velocity profile is developed and used to show the sensitivity of log-law methods to the coefficients assumed. It is also shown that the effects of changes in duct cross-sectional area seriously affect the relationship between wall shear stress and pressure gradient in fully developed flows.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, Dept. of Engineering|
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