Combining Individual Scour Components to Determine Total Scour (2018) / Chapter Skim
Currently Skimming:
Pages 54-80
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 54... ...
54 CHAPTER 3. Research Methodology 3.1 Introduction The research was organized into three integrated components including both experimental and computational studies.
|
From page 55... ...
55 3.2 Experiments at Georgia Tech 3.2.1 Experimental Setup Hong (2013) completed a comprehensive set of experiments on a modified laboratory crosssection based on the Towaliga River model described previously and shown in Figure 2-16.
|
From page 56... ...
56 constructed of hand-compacted 1.1 mm sand with a 2:1 side slope and a spill-through abutment shape. A few experiments were conducted with a solid 45º wingwall abutment.
|
From page 57... ...
57 0.375 10.725 0.90 0.375 2.40 0.40 0.75 0.375 Flow Flow Figure 3-3. Top and side views of model bridge deck (dimensions in inches at 1:45 model scale)
|
From page 58... ...
58 The point gage and a calibrated capacitance wave gage (RBR Ltd. Model WG-50)
|
From page 59... ...
59 series of runs for La/Bf =0.53 was added for further study of vertical contraction and pier scour interactions. The embankment on the right floodplain was maintained at a constant length with the abutment toe terminating at the upper edge of the main channel bank (La/Bf = 1.0)
|
From page 60... ...
60 scour with no abutments so that La/Bf = 0. Runs 23-27 were conducted for forty-five degree wingwall (WW)
|
From page 61... ...
61 Run La/ Bf Flow type 1 1 fc f V V 1 1 mc m V V 1 1 m f Y Y W L p Q Qot Q, cfs T.W. elev., ft Scour components A P L V 17 OT 0.622 0.784 0.664 0.407 6.5 1.714 *
|
From page 62... ...
62 contraction scour alone. The first column of the table shows how the various components of scour were combined in different collections of experiments to study total scour with interactions.
|
From page 63... ...
63 Table 3-2. Experimental runs organized by combinations of scour components 0.41 0.77 0.53 1 2 3 4 5 6 7 8 9 10 11 12 14 15 16 17 18 19 20 22 23 24 25 26 27 28 29 30 31 32 33 35 36 37 38 39 40 41 42 43 44 45 Type of Flow F SO OT F OT F OT F OT F SO OT F OT F OT F SO OT F SO OT SO SO SO SO SO SO OT SO SO OT F SO F SO F SO SO Pier Location (L p/W )
|
From page 64... ...
64 The prediction of combined abutment scour and lateral contraction scour in free flow with a formula of the same type has been suggested previously by Sturm (2006) and Ettema et al.
|
From page 65... ...
65 which pivot about a central support as controlled by screw jacks to adjust the flume slope. Flow straighteners are located at the inlet of the flume, and a weir downstream of the flume controls tailwater elevations.
|
From page 66... ...
66 Figure 3-5. Schematic of compound channel cross section in 8-ft wide Auckland CWS flume.
|
From page 67... ...
67 Two batches of sediment were used for the movable bed sections in both the CWS and LBS flumes. Their gradation curves were nearly identical.
|
From page 68... ...
68 flume at the approach flow section designated as Cross Section 1 (C.S.
|
From page 69... ...
69 Table 3-3. Experimental conditions for LBS experiments in the UoA 5-ft wide flume (Bf/Bm = 2.3)
|
From page 70... ...
70 Table 3-4. Experimental conditions for CWS experiments in the UoA 8-ft wide flume (Bf/Bm = 2.0)
|
From page 71... ...
71 3.4 Computer Modeling at Cardiff University In this project, the in-house code HYDRO3D (Stoesser and Nikora 2008, Stoesser 2010, Bomminayuni and Stoesser 2011) was employed to achieve the project objectives related to the role of turbulence in combined scour processes.
|
From page 72... ...
72 The resulting governing equations for simulation of the large scales become: 0 i i x u (3-5)
|
From page 73... ...
73 liquid gas xif xif xif tx 0 0 0 )
|
From page 75... ...
75 here. Temporal and spatial derivatives in the RANS mode are calculated in exactly the same manner as in the LES mode.
|
From page 76... ...
76 Figure 3-7 Computational domain of the numerical simulations of execution. The grid employed for all simulations uses approximately 50 million grid points, regardless of the case.
|
From page 77... ...
77 condition is applied. At the inlet a fully-developed compound channel flow field is prescribed.
|
From page 78... ...
78 Table 3-6: Resolution of the Immersed Boundaries Case Bridge deck Abutments MC Scour Total LES_LSA_Medium 52x103 175 x103 261 x103 - 488 x103 LES_SSA_Medium 52 x103 259 x103 261 x103 - 572 x103 LES_LSA_Fine 318 x103 2.1 x106 608 x10 - 3 x106 LES_Scour_Fine 318 x103 2.1 x106 608 x103 731 x103 3.7 x106 3D_RANS_LSA - 12 x103 43 x103 - 55 x103 3D_RANS_SSA - 18 x103 43 x103 - 61 x103 * MC – Main Channel, FP – Floodplain 1 varies between cases, depending on flow depth 3.4.5 Pre-Cursor Simulations Pre-cursor simulations were performed for both LES and 3D RANS with the objective to provide realistic inflow conditions for the main simulation.
|
From page 79... ...
79 Figure 3-8: Domain of the compound channel of the pre-cursor simulations in plain view Fig. 3-9 presents both the instantaneous and time-averaged streamwise velocity contours in a cross-section.
|
From page 80... ...
80 Figure 3-9: Contours of the instantaneous (top) and time-averaged streamwise velocity in the cross-section of the compound channel Figure 3-10: Measured (dots)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.