Cover Image

Not for Sale



View/Hide Left Panel
Click for next page ( 54


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 53
53 2 1 Flow 1.5 0.5 Y/B Y/B 1 0 1.34 1.00 1.68 0.33 2.35 0.5 5.10 0.33 = 0.67 -0.5 0.33 0.33 0.33 0.33 -1 0 -1 -0.5 0 0.5 1 1.5 -1 -0.5 0 0.5 1 1.5 X/B X/B Figure 6.18. Bed shear stress contours (N/m2) around a Figure 6.16. Velocity field around a rectangular pier with rectangular pier (L/B = 0.25). L/B = 0.25. 2 1 Flow Flow 1.5 0.5 Y/B Y/B 0 1 1.15 0.88 1.34 = 0.74 0.47 1.56 0.33 -0.5 0.5 0.33 0.33 0.33 0.33 -1 0.33 0 -1 -0.5 0 0.5 1 1.5 -1 -0.5 0 0.5 1 1.5 X/B X/B Figure 6.17. Velocity field around a rectangular pier with Figure 6.19. Bed shear stress contours (N/m2) around a L/B = 4. rectangular pier (L/B = 1). stress tends to increase with the attack angle. They also show 2 that the location of the maximum shear stress moves back- ward along the side of the pier as the attack angle increases. 1.5 Flow 6.12 ATTACK ANGLE EFFECT ON MAXIMUM SHEAR STRESS 0.59 Y/B 0.68 1 0.95 1.12 The maximum shear stress max is the maximum shear = 0.77 1.30 0.51 0.33 stress that exists on the riverbed just before the scour hole 1.56 0.33 0.5 starts to develop. One way to present the data is to plot 0.42 max/max(0 degree) as a function of (Figure 6.26). The param- 0.33 eter max(0 degree) is the value of max for the case of a pier in line 0 with the flow in deep water and is given by Equation 6.1. The -1 -0.5 0 0.5 1 1.5 X/B attack angle correction factor, ksh, is the ratio max/max(0 degree). The data points on Figure 6.21 correspond to the results of Figure 6.20. Bed shear stress contours (N/m2) around a the five numerical simulations. By regression, the equation rectangular pier (L/B = 4).