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Federal Highway Administration Research and Technology
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Scour development is especially complicated by the presence of large-scale turbulence structures. The roles that such turbulence structures play in pier scour have been only partially appreciated. Turbulence structures, together with local flow convergence/contractions, around the broad fronts and flanks of piers, or between piles of complex pier configurations, are erosive flow mechanisms of primary importance. This device applies various turbulent/dynamic hydraulic loading conditions to a range of different cohesive soils and measures the soil erosion response. The turbulent hydraulic loading is characterized by fluctuating/oscillating shear and normal forces. The dual-drive wave making tube uses dual pistons in a tube to oscillate a water body over soil samples. The device generates turbulent/dynamic hydraulic loading conditions to a range of different cohesive soils. The soil samples in the test section are mounted on a sensor that simultaneously measures shear stresses and vertical forces. It is automated with LabVIEW codes and can produce programmed cyclic flow conditions.
|The wave making tube.||Test chamber of the wave making tube.|
The force balance flume is 45 feet long and 14 inches wide. In this configuration, a discharge rate of over 900 gallons per minute can be achieved. It has a force balance device that is used to determine lift and drag coefficients for inundated bridge decks. This flume can be easily modified into a wave channel by mounting a paddle to the existing two-dimensional shaker while the flume is filled with still water. It has an apparatus that allows for measuring the movement of a bridge deck model using a motion capturing technique and various sensors while it is being hit by waves. The flume uses a two-axis robot to measure the velocity distribution using Ultrasonic Doppler Velocimetry (UDV) transducers.
|View of the force balance flume.||View of the force balance tower.|
The fish passage flume is 29 feet long and 18 inches wide. In this configuration, a discharge of 700 gallons per minute can be achieved. The flume is tiltable up to 2.6 degrees. Different sections of a corrugated pipe can be inserted into the flume to measure and visualize the flow distribution at any cross section. The flume uses a two-axis robot to measure the velocity distribution using an Acoustic Doppler Velocimeter (ADV) probe. Two-dimensional, three-component Particle Image Velocimetry (PIV) can be performed in this flume.
|View of the fish passage culvert flume.||View of the corrugated pipe inside the fish
passage culvert flume.
The tilting flume is 70 feet long and 6 feet wide and has a sediment recess for highway- related scour experiments. The maximum discharge of this flume is 3,000 gallons per minute. The flume uses a three-axis carriage to measure the velocity distribution using an Acoustic Doppler Velocimeter probe and to map any scouring that has occurred in the sediment recess using a laser distance sensor.
|View of the tilting flume.||View of the tilting flume’s carriage system.|
The ex situ scour test device is 36 inches long and 14 inches wide. A special flow distribution can be archived within a 1 to 2- centimeter high gap through the combination of thrust created by a moving belt and the normal pump pressure. In this configuration, a velocity of 6 meters per second can be achieved. Soil samples are mounted on shear and normal force sensor while pushed into the flow to account for the steady abrasion that occurs. Two-dimensional, two-component (2D-2C) PIV can be performed in this flume.
|View of the ex situ device.||The shear stress sensor mounted under the ex situ device|
This study develops a scour testing field device, the in situ scour testing device (ISTD), to determine the erodibility of soils around bridge foundations. An effective in situ scour testing device could more accurately define the scour potential for a given set of hydraulic design conditions. The ISTD will support the development and implementation of the next generation of scour evaluation guidelines.
|The lab-ISTD is a laboratory version of the in situ scour testing device (ISTD) concept. The cylindrical erosion head of the lab-ISTD produces shear stresses induced by radial flow. The erosion head is specially designed to ensure uniform distribution of shear stresses across the soil surface. The erosion head stays stationary and the erosion rate is determined by advancing a piston on which the soil specimen is mounted.||The portable demo-ISTD was designed to demonstrate the concept of the in situ scour testing device at conferences and exhibitions.|
The laboratory has the ability to perform 2D-2C and 2D-3C PIV in numerous flumes. In the past, the lab only used a 15Hz, 120mJ YAG laser and two cameras with 960 by 960 pixels to perform PIV experiments. In the near future, an additional system will be available to perform 2D-2C and 2D-3C PIV with much higher speeds (200 to 300Hz) and larger images (1280 by 1024) using a new 200W laser and new high-speed cameras.
|View of an illuminated cross section of a submerged bridge deck while performing two-dimensional, two-component (2D-2C) PIV.||View of two-dimensional, three-component (2D-3C) PIV experimental setup.|
The new PIV system allows data acquisition rates of up to 500Hz with two cameras at full resolution. This will allow high-resolution recordings of the complicated flow patterns around bridge foundations. The new time resolved PIV system will primarily be used to compare flow fields with CFD models and to calibrate CFD models.
|A new PIV system capable of time-resolving PIV measurements is being developed.|
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Turner-Fairbank Highway Research Center
6300 Georgetown Pike
McLean, VA 22101-2296
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