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Overview | Projects | Laboratory Physical Modeling | Laboratory Numerical (CFD) Modeling | Ongoing Laboratory Activities
Hydraulics Laboratory Personnel | Research Publications | Office of Bridge Technology: Hydraulics

 

 

J. Sterling Jones Hydraulics Research Laboratory

 

Hydraulics Laboratory Physical Modeling

Dual-Drive Wave Making Tube

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 photo shows the Dual-Drive Wave Making Tube with the control electronics. The photo shows a closeup of the testing chamber of the dual-drive wave making tube. It is made of clear material to allow observation of the erosion process as well as potential Particle Image Velocimetry (PIV) measurement. The chamber has opening for the installation of the force sensor.
The wave making tube. Test chamber of the wave making tube.

 

Force Balance Flume

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.

The picture shows the 45-foot-long and 14 inch-wide force balance flume looking from the downstream end. The picture also shows the flap gate to control the water level in the flume. The picture shows the Force Balance Tower. A model of a bridge deck is mounted inside the Force Balance Tower and lowered into the flume.
View of the force balance flume. View of the force balance tower.

 

Fish Passage Culvert Flume

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.

The picture shows the Fish Passage Culvert Flume from the downstream end. The upper part of the flume is tiltable. The water falls over a flap gate into a tank under the flume. The picture shows the channel of the Fish Passage Culvert Flume. A corrugated pipe is installed inside the channel and water runs through it.
View of the fish passage culvert flume. View of the corrugated pipe inside the fish
passage culvert flume.

 

Tilting 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.

The picture shows the tilting flume from the downstream end. In the middle of the flume there is a recess filled with sand for scour experiments. The picture shows the carriage from the tilting flume. The carriage is a three-axis robot resting on two rails on top of the tilting flume; it has an ADV probe and a laser distance sensor mounted to it.
View of the tilting flume. View of the tilting flumeā€™s carriage system.

 

Ex Situ Scour Testing Device

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.

The photograph shows the ex   situ testing device from a side view. In a top box you can see a belt drive with the test channel underneath it. The photograph shows the shear stress sensor mounted at the bottom of the ex situ testing device. A soil sample placed inside of it is pushed through the bottom of the flume into the test channel.
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 Laboratory In situ Scour Testing Device (Lab-ISTD) was designed to measure the erodibility of soils in a laboratory. A tested soil is accommodated in a transparent plexiglas tube with an inner diameter of three inches. The tube is half filled with sandy soil. A cylindrical erosion head with a diameter of 2.5 inches is fixed in the test tube above the soil. The specially designed erosion head ensures uniform distribution of shear stress across the soil surface. Four ultrasonic doppler velocimetry (UDV) probes reside in the erosion head. The probes measure the distance between the erosion head and the soil surface. During a test, the distance is kept constant by using a motor to push up the soil in the test tube. Water flows down through the 0.25-inch gap between the test tube and the erosion head. Water then flows radially toward the center of the erosion head. These radial flows generate horizontal shear stress to erode soils. In the center of the erosion head, an 8 millimeter-diameter hole guides water out of the test tube. The pump power together with the distance between the erosion head and the soil surface can vary the magnitude of the shear stress acting on the tested soil. The Demo-ISTD consists is a smaller version of the Lab-ISTD and was designed in order to demonstrate the erosion concept of the In Situ Scour Testing Device within a laboratory, classroom or fair setting. The ITEM frame holds a transparent plexiglas tube with an inner diameter of 50 mm. The tube is half filled with cohesive soil and is connected to a piston that moves up and down. A cylindrical aluminum erosion head inside the tube with an outer diameter of 45 mm is fixed above the soil and includes a 3D printed PLA plastic erosion chamber at the bottom that is shaped to allow uniform concentric flow. In the center of the erosion head, an 8 mm diameter hole guides water out of the test tube. The specially designed erosion head ensures uniform distribution of shear stress across the soil surface. It does this by directing water flow towards the center of the erosion chamber from the gaps between the test tube and erosion head. A pump station that recirculates water in the system consists of a sucking pump, pressure pump and a water tank. A control unit is connected with the frame and the pump station and allows the engineer to control the device in a manual or pc-controlled remote view. A certain distance is maintained between the bottom of the erosion head and the soil surface by measuring the pressure difference between the inflow towards the erosion chamber and outflow that runs out of the test tube.
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.

 

Hydraulics Laboratory Particle Image Velocimetry (PIV) System

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.

The photograph shows a model of a bridge deck submerged in water. A cross section of the bridge deck is illuminated by a laser. Particles within this light sheet are reflecting the light. The photograph shows a 2D-3C PIV setup. It shows two cameras mounted on top of the flume in an angle towards a cross section of the flume. From the front, a laser illuminates the cross section with a light sheet. Particles in the flow crossing the light sheet reflect the laser light.
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.

 

Enhanced Particle Image Velocimetry (PIV)

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.

The photograph shows the new dual 10kHz high-speed laser on the left. The unit on the right is a chiller that keeps the laser coolant at a constant temperature of 26 degrees Celsius. The unit in the back provides the voltage and trigger impulses for the laser.
A new PIV system capable of time-resolving PIV measurements is being developed.

 

Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000