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Chapter 5 - Test results
5.1 Introduction
The present section briefly describes the obtained results and special observations that were made
during the tests. The first section (§ 5.2) presents the preliminary tests, which served to establish
the whole test procedure and to adjust and refine the measurements and the measurement technique.
The main tests, described in section 5.3 are made for different bed slopes, discharges and
rib-spacings. Finally an additional set of tests was performed to study the influence of the depth of
the macro-roughness elements (§ 5.4). A detailed analysis of the tests is performed in chapter 6.
Some limits were fixed for the tests:
• The flow regime is maintained subcritical (Froude < 1).
• The maximum discharge of the pumps was of 210 l/s.
• The discharge had to be big enough in order to obtain any sediment transport.
All these conditions were evaluated in the following table, which shows the sediment transport
rate in g/min. The underlayed zones (in the right part of the table) represent Froude numbers
higher than 0.8, 0.9 and 1.0. Two lines were added to the plot to indicate the used minimum and
maximum discharge. On the horizontal axis, the bed slope is given, and on the vertical one, the
flow depth. The domain of the tests is highlighted with bold characters (center of the table). Since
the armoring layer is destroyed in the beginning of the tests, the following table gives the sediment
transport rates without armoring (with d 30
= 4.4 mm, d m = 8.5 mm, d 90
= 14.8 mm).
hw Qb [g/min]
[m] So = 0.2% So = 0.3% So = 0.35% So = 0.4% So = 0.45% So = 0.5% So = 0.55% So = 0.6% So = 0.65% So = 0.7% So = 0.8% So = 0.9%
0.05 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
0.06 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
0.07 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
0.08 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 605
0.09 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 508 4 257
0.10 - - - - - - - - - - - - - - - - - - - - - - - - - - - 927 3 704 7 211
0.11 - - - - - - - - - - - - - - - - - - - - - 17 1 232 2 653 6 122 10 440
0.12 - - - - - - - - - - - - - - - - - - 16 1 288 2 794 4 537 8 742 13 922
0.13 - - - - - - - - - - - - - - - - - - 1 121 2 670 4 485 6 568 11 550 17 636 Q=150
0.14 - - - - - - - - - - - - - - - 768 2 314 4 155 6 294 8 734 14 531 21 566
0.15 - - - - - - - - - - - - 275 1 770 3 588 5 735 8 213 11 026 17 673 25 697
0.16 - - - - - - - - - - - - 1 091 2 836 4 938 7 403 10 234 13 436 20 964 30 015 Q=210
0.17 - - - - - - - - - 338 1 956 3 961 6 358 9 153 12 350 15 954 24 396 34 507
0.18 - - - - - - - - - 1 016 2 868 5 142 7 845 10 981 14 556 18 575 27 959 39 163
0.19 - - - - - - 86 1 729 3 823 6 375 9 393 12 881 16 846 21 292 31 645 43 974
0.20 - - - - - - 620 2 475 4 819 7 657 10 999 14 849 19 214 24 099 35 448 48 929
0.21 - - - - - - 1 178 3 253 5 852 8 986 12 660 16 882 21 657 26 992 39 360 54 021
0.22 - - - 11 1 759 4 059 6 922 10 357 14 373 18 975 24 170 29 965 43 375 59 242
0.23 - - - 421 2 362 4 893 8 026 11 770 16 134 21 125 26 750 33 015 47 488 64 586
0.24 - - - 848 2 986 5 754 9 163 13 222 17 942 23 329 29 392 36 136 51 693 70 045
0.25 - - - 1 289 3 630 6 639 10 329 14 711 19 793 25 585 32 093 39 326 55 987 75 614
0.26 - - - 1 745 4 292 7 548 11 525 16 235 21 686 27 889 34 852 42 580 60 363 81 287
0.27 - - - 2 215 4 972 8 479 12 748 17 791 23 619 30 240 37 664 45 897 64 819 87 060
0.28 - - - 2 697 5 669 9 431 13 998 19 380 25 589 32 635 40 527 49 272 69 351 92 927
0.29 - - - 3 192 6 382 10 404 15 272 20 998 27 595 35 072 43 438 52 702 73 954 98 884 Fr > 1.0
0.30 - - - 3 698 7 110 11 396 16 570 22 646 29 635 37 549 46 397 56 187 78 626 104 927
0.31 - - - 4 215 7 853 12 406 17 890 24 320 31 708 40 064 49 399 59 722 83 364 111 052
0.32 - - - 4 743 8 609 13 433 19 233 26 021 33 812 42 616 52 444 63 306 88 164 117 255
0.33 8 5 282 9 379 14 478 20 596 27 747 35 945 45 202 55 529 66 936 93 024 123 533
0.34 215 5 830 10 161 15 538 21 978 29 497 38 107 47 822 58 654 70 611 97 941 129 883
no sediment transport sediment transport Fr > 0.8 Fr > 0.9
Table 5.1: Computed sediment transport capacity (without armoring) - overview over the test domain
Q b , Fr and h w
Table 5.2 gives the same information but computed with an armoring layer (computed according
to Gessler, 1990, see section 3.3, d 30
= 5.5 mm, d m = 11.5 mm, d 90
= 18.1 mm). This allows
page 100 / November 9, 2002
Wall roughness effects on flow and scouring