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8,366 results on '"Boundary Layer"'

3. Two parameter integral methods in laminar boundary layer theory

Author

Lister, William Macrae and Curle, S. N.

Subjects
515, QA913.L5, Boundary layer
Abstract

The work of this thesis is concerned, with the investigation and attempted improvement of an integral method for solving the two dimensional, incompressible laminar boundary layer equations of fluid dynamics. The method which is based on a theoretical two parameter representation of well-known boundary layer properties was first produced by Professor S. N. Curle. Its range of application, reliability and accuracy rely on four universal functions which have been derived from known exact solutions to the boundary layer equations, and are given tabulated in terms of a pressure gradient parameter λ. This thesis seeks to improve these properties by making adjustments to the tabulated functions and also considers the extension of the method to certain compressible boundary layer problems. The first chapter contains the development of, and background to the method and gives a critical assessment of the existing functions. This analysis indicates that the method may be improved by supplying more data for certain ranges of λ from which the functions may be calculated; by improving the fitting process; and by the provision for small values of λ of an analytic form for a shape parameter H which the method involves. To supply more data two new solutions for the flows u₁ = U₀ (1+ξ) and u₁ = u₀ (ξ+ξ³) where ξ is a non-dimensional co-ordinate in the direction of the flow, are investigated. The resulting work produces some interesting examples of the use of series expansions in boundary layer theory and these, and the results produced, are given in the second chapter. The fitting of the functions is carried out in chapter three. Polynomial models in terms of λ are fitted by least squares techniques to data from seven solutions and are adjusted to ensure an analytic form for H for small values of λ. A comparison of results using new and old tables Indicates that an improvement has been made. The transformation relating certain compressible and incompressible flows is next examined and the extension of the method to such problems considered. An idea due to Stewartson for assessing the relative accuracies of methods under such circumstances indicates that the method should be highly accurate, a result confirmed by the calculation of the compressible flow u₁ = u₀ (1-ξ) at a leading edge Mach number of four. The thesis is concluded with a review of the work carried out and the results obtained.

Published
1971

36. Theory of Viscous Fluids

Author

von Mises, Richard, Friedrichs, Kurt O., John, Fritz, editor, Sirovich, Lawrence, editor, LaSalle, Joseph P., editor, von Mises, Richard, and Friedrichs, Kurt O.

Published
1971
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50. Effect of Preston Tube Diameter to Accurate Estimation of Flow Resistance in Smooth Rectangular Open Channel

Author

Masoomeh Fatahi, Babak Lashkar-Ara, and Mohammad Zaker Moshfegh

Subjects
preston tube, patel, bechert, boundary layer, skin friction, Hydraulic engineering, TC1-978, Irrigation engineering. Reclamation of wasteland. Drainage, TC801-978
Abstract

In this paper, the effect of tube diameter (Dp) in measurement of shear stress (tb) of the boundary layer wall was investigated under a zero pressure gradient. For this purpose, four different tubes with outside diameters of 3.2, 3.9, 4.7 and 6.3 mm were used which are corresponded to Dp/d of 0.039, 0.047, 0.057 and 0.076, respectively. Measurement of the pressure difference of static point and total in Preston tube was implemented using a differential pressure transducer with accuracy of 0.2 percent of the original scale. The results of the shear stress measurements around Reynolds numbers from 6.4×104 to 39.87×104 using Patel and Bechert calibration equations showed that the Preston tube diameter has a significant impact on the shear stress estimation and both equations are sensitive to the tube diameter. The maximum value of difference in the shear stress measurements tb of different tubes using Patel calibration is about 9%, while the Bechert calibration gives a maximum difference of approximately 14%. Comparing results obtained from both Patel and Bechert calibration equations showed that variation in result of the two equations is minimum when the diameter Preston tube is 3.9 mm.

Published
1970
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