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Additional tests
observations. All necessary precautions have been taken to limit their impact on the results and to
ensure a relyable dataset.
For the tests with macro-roughness, vertical ribs were placed at the outer side wall with a regular
spacing. The last meter in the inlet upstream the bend as well as the first two meters in the outlet
reach, downstream the bend, were also equipped with ribs. The spacing between ribs increased
with increasing distance from the bend with a factor 2 compared to the previous spacing
(Fig. 5.3). The following table gives the spacings of the ribs for the different tests:
TEST
[°]
e s
e s e s
INLET [MM]
DIST. TO BEND
BEND [°]
OUTLET [MM]
DIST. TO BEND
B2, C2, D2, E2 4° 384, 1026* 0.6, 4.6, ..., 88.6 298, 752, 1394
B3, C3, D3, E3 2° 157, 478, 932** 0.6, 2.6, ..., 88.6 71, 298, 525, 752, 979, 1300,
1754
B4, C4, D4 1° 43, 203, 429, 749 0.6, 1.6, ..., 89.6 70, 183, 296, ..., 974, 1134,
1360, 1680
E5 8° 838, 2121 0.6, 8.6, ..., 88.6 752, 1815
Table 5.7:
Spacing of the macro-roughness
* 384, 927mm for test B2, ** 157, 379, 693, 1137mm for tests A2 and B3
2 B
e s
2
e s
Figure 5.3: Macro-roughness arrangement in the straight transition zones in the inlet and outlet reach
5.4 Additional tests
A series of additional tests was performed during the month of May and June 2001 in the frame
set of a diploma work by GÜNTHER (2001). The aim of these tests was to examine the influence of
the macro-roughness thickness on the scour depth. Therefore the vertical ribs were modified and
a rectangular, 20 mm thick wooden bar was mounted between the side wall and the macro-roughness.
Fig. 4.11 in paragraph 4.2.1.d) shows the two type of rib geometries: on the left side, the one
for the main tests and on the right side the one for the additional tests.
The tests followed exactly the same procedure like the main tests (§ 4.5), yet without velocity measurements
and without sediment sampling at the outlet. The results are presented with the main
tests in the different Appendix (usually in section *.4).
EPFL Ph.D thesis 2632 - Daniel S. Hersberger November 9, 2002 / page 111