Figure 3. Bed level change contours after and before incipient open-bed scour flow around the wing-wall abutment model with length L into the flow without scAUR™ and VorGAUR™ products. Flow from left to right.
Figure 6. Bed level change contours after and before flow around the untreated spill-through model (L=6.25”, 159mm). Note the dark blue scour hole due to the free-surface vortex.
Figure 2. Bed elevation contours around a vertical-wall abutment and a scAUR™ abutment (L is the protrusion length and y is the bed elevation)
Figure 5. Bed level contours around the modified wing wall abutment model with VGs (length L=6.25”). No scour observed at any location.
With a scAUR™ modified wing-wall abutment with VorGAUR™ VGs, there is not only no scour around the model base, but there is no open-bed scour hole farther downstream of the model around x/L = 2, as shown in Figure 5. This is the effect of VGs on the surface vortex which caused the scour hole farther downstream of the unmodified model in Figure 3. The VGs generate the counter-rotating vortices which diffuse and reduce the strength of the surface vortex. Thus, no scour occurred around the contraction and near the base of the modified wing-wall abutment with VGs and there is no scour farther downstream of the model.
scAUR™ Product Model Tests for
Bridge Abutments
The same wing-wall abutment flume model that was tested above was modified with scAUR™ and VorGAUR™ products, as shown in Figure 4. A test was performed under the same flow conditions and flume geometry as for the wing–wall abutment without scAUR™ and VorGAUR™ products that is discussed above. The effects of the scAUR™and VorGAUR™ products are to bring lower velocity flow up from the flume bottom and prevent the scour around the bottom of the abutment.
Case Four: scAUR™ with VorGAUR™ Spill-Through abutment model
Test conditions:
Abutment Model Type: AUR model
Flow Speed: 0.61 m/s; Incipient Scour Condition
Pea Gravel Density: 3 specific gravity; 1/8" < Pea Gravel Size < 1/4"
Ratio of Protrusion Length to Water Depth:1.0
Test results:
Results for the spill-through abutment flume model without scAUR™ and VorGAUR™ products is shown in Figure 6. It has a 45 deg slope and was tested under the same conditions as the wing-wall abutment above. There was a free surface level difference before and after the contraction leading edge due to the free surface vortex formation. The local scour close to the model is very weak while a large scour hole was generated downstream of the model (x/L = 1.25-2.5 and z/L = 1) as shown in Figure 6. It is caused by a stronger surface vortex shed from the model or closer to the bed than by the wing-wall abutment.
The spill-through abutment flume model with scAUR™ and VorGAUR™ products is shown in Figure 7. The scAUR™and VorGAUR™ products bring lower velocity flow up from the flume bottom. The VGs diffuse the surface vortex by creating counter-rotating vortices and prevent the downstream scour around the bottom of the abutment. Figure 8 shows no scour around the upstream contraction and near the base of the modified spill-through abutment due to the fairing. Although there is still a very minor scour at the downstream of the model, its max depth (-0.02L) is about the size of one pea gravel and is much lower than that for an untreated abutment. No scour occurred around the contraction and near the base of the modified wing wall with VGs. The open bed scour due to the free surface vortex has been prevented by the vortex generators.
Case One: scAUR™ with VorGAUR™ abutment model
Test conditions:
Abutment Model Type: AUR model
Flow Speed: 0.61 m/s; Incipient Scour Condition
Pea Gravel Density: 3 specific gravity; 1/8" < Pea Gravel Size < 1/4"
Ratio of Protrusion Length to Water Depth:2.88
Test results:
The left plot in the figure immediately below shows the bed elevation result of the flume test of a vertical-wall abutment with the protrusion length to water depth ratio equal to 2.88. Two large scour holes occur around the vertical-wall abutments. The upstream scour hole is caused by the primary vortex and the downstream scour hole is caused by the wake shedding vortices.
The right plot in the figure below presents the case that the scAUR™ fairing is secured around the vertical abutment to suppress and control the primary vortex and VorGAUR™ devices are attached to the fairing surface to control downstream flow separation in the wake region. The results demonstrate that with the scAUR™ fairing and VorGAUR™ devices around the abutment, the upstream scour hole is eliminated and the downstream scour hole is greatly suppressed by at least 80%.
Figure 8. Bed level change contours after and before flow around the scAUR™ modified sharp edge spill through model with 8 VorGAUR™ VGs (L=9”, 229mm).
Figure 4. scAUR™ with VorGAUR™ modified wing wall abutment model with vortex generators (VGs) before the test. Pea gravel of 3.2-6.4mm in size.
Case Two: scAUR™ with VorGAUR™ abutment model
Test conditions:
Abutment Model Type: AUR model
Flow Speed: 0.61 m/s; Incipient Scour Condition
Pea Gravel Density: 3 specific gravity; 1/8" < Pea Gravel Size < 1/4"
Ratio of Protrusion Length to Water Depth:1.0
Test results:
A second vertical-wall abutment with the protrusion Length to water depth ratio equal to 1.00 is evaluated in flume tests, as shown in the figure below. Results again demonstrate that with the scAUR™ fairing and proper installation of VorGAUR™ devices, the upstream scour is eliminated and the downstream scour hole is greatly suppressed. Please contact us, if you are interested in the flume test videos.
Figure 1. Bed elevation contours around a vertical-wall abutment and a scAUR™ abutment (L is the protrusion length and y is the bed elevation)
Figure 7. Modified sharp-edge spill-through abutment model with VGs in the AUR flume. Pea gravel of 3.2 to 6.4mm in size.
Case Three: scAUR™ with VorGAUR™ Wing-Wall abutment model
Test conditions:
Abutment Model Type: AUR model
Flow Speed: 0.61 m/s; Incipient Scour Condition
Pea Gravel Density: 3 specific gravity; 1/8" < Pea Gravel Size < 1/4"
Ratio of Protrusion Length to Water Depth:1.0
Test results:
Results for a wing-wall abutment flume model with 45 deg wings without scAUR™ and VorGAUR™ products is shown in Figure 3. Local scour occurred around the contraction leading edge of the model and the maximum local scour depth is located very close to the contraction edge. The scour depth contours are normalized by the model length L. The maximum scour hole depth and mound height are approximately -0.13L and 0.12L, respectively.