U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
The MFS features a 90-foot-long by 13-foot-wide tiltable working platform for experimental setups. Channel sections of 3- or 6-feet wide can be mounted on the working deck. Both channel section alternatives include a 27-foot-long sediment recess test section. If needed, other hydraulic structures such as culverts, pipes, and drainage systems can be installed and tested. The flume system also includes a 27-foot-long flow inlet headworks and a carefully designed outlet section that includes a sediment trap. The sediment recirculating system, which is the only one of its kind in the United States, consists of an inclined auger, conveyor belt, and sediment infeed hopper. Diaphragm pumps push sediment from the infeed hopper into the flume through computationally-optimized and 3D-printed infeed nozzles located at the bottom of a specially-designed channel section. This sediment recirculation capability allows for much more realistic river flow modeling. The pump discharge capacity of the MFS is 30 cubic feet per second (ft3/s). An automated instrumentation carriage and industrial robot carriage system hold sensors needed to measure flow and sediment transport/scour data, and to assist with the setup of experiments. The main purpose of the experiments in the MFS is to calibrate computational fluid dynamics (CFD) models for further analysis and development of guidelines.
Figure 1. View of the MFS.
|Figure 2. View of the MFS’s industrial robot carriage system.|
The force balance flume is 36 feet long and 15 inches wide. In this configuration, a discharge rate of over 3 ft3/s can be achieved. An industrial robotic arm is utilized on the FBF to hold sensors for measuring flow properties and to act as a temporary force balance for the study of hydro-dynamic loads on structures until a new force balance tower is installed. The proposed force balance tower will also be used to study hydraulic erosion forces on 3D-printed bridge foundation scour forms. The main purpose of the FBF is to perform high-precision force measurement experiments to calibrate CFD simulations. The goal of these experiments is researching and analyzing hydro-dynamic loads/forces responsible for scour and erosion around bridge foundations in order to improve scour prediction estimates for the new scour design vision.
|Figure 3. View of the Force Balance Flume|
|Figure 4. 3D Rendering of Proposed Force Balance Tower.|
The operational concept of the ISTD is as follows (see figure 5):
|Figure 5. ISTD Operational Concept
Downward-facing blue arrows illustrate step 2;
red arrows indicate step 3; upward-facing blue arrows show step 4.
The ISTD/laboratory Drill Rig zone is used to test and improve the erosion device before field deployment, and is used to develop the next generation of in situ soil erosion resistance testing devices. The next generation will utilize robotics to improve future scour depth limit state equations for the new scour design vision.
|Figure 6. View of ISTD and Laboratory Drill Rig.|
|Figure 7. Erosion Head being inserted into casing.|
Multiple devices and tools are utilized in this laboratory zone including the ex situ scour testing device laboratory (ESTD) and various soil preparation and geotechnical testing apparatuses. Details about the main apparatus of the ESTD are given below.
|Figure 8. View of the lab’s Soil Erosion Testing Devices zone.|
Ex Situ Scour Testing Device (ESTD)
The ESTD measures the erodibility of a cylindrical soil specimen under well-controlled flow conditions. It has an overall dimension of 15-feet long, 6-feet wide, and 5.3-feet high. Its rectangular testing channel has a dimension of 3-feet long, 4.7-inch wide, and 0.75-inch high. The maximum flow rate in the ESTD is 0.5 ft3/s, which translates to a maximum average flow speed of 20 ft/s in the testing channel. The ESTD features an innovative shear stress sensor that can instantaneously measure the bed shear stress during the erosion process. The system can accommodate a 1-foot-long field soil sample in a Shelby tube with a 3-inch outer diameter. The soil can be automatically pushed up by a hydraulic piston as the erosion progresses. The extrusion is controlled by quasi-instantaneous detection of the soil surface change using an underwater laser scanner held by an industrial robot.
Soil erosion resistance testing is a part of the new scour design vision and is needed to determine the scour depth limit state. The vision of zone 4 is to develop and demonstrate a fully-automated soil erosion resistance testing laboratory which utilizes a robotic assembly line that can be deployed in the field.
|Figure 9. View of the ex situ scour testing device (ESTD).|
Particle Image Velocimetry (PIV) is an optical method of flow visualization used for many research activities in the Hydraulics Laboratory. It is used to obtain instantaneous velocity measurements and related flow properties. The flow is seeded with tracer particles that, for sufficiently small particles, are assumed to faithfully follow the flow dynamics. The flow with entrained particles is illuminated so that particles are visible. The motion of the seeding particles is used to calculate speed and direction (the velocity field) of the flow being studied.
The Hydraulics Laboratories PIV system can be used for 2D-2 Components and 2D-3 Components Time Resolved PIV (TPIV). The Laboratories Litron LPY laser has a pulse energy of 50mJ and consists of two parallel laser systems, each capable of creating 200 pulses per second, that allow for the usage of TPIV. Special laser optics can create light sheets that are from 1- to 3-mm thick, illuminating the cross section of the flow that needs to be visualized. Hollow glass spheres (with a diameter of 10 to 110 microns) covered with silver oxide are used as tracer particles. High-speed cameras are utilized to detect the motion of the particles and to measure the velocity flow field.
|Figure 10. View of an illuminated cross section of a submerged bridge deck while performing two-dimensional, two-component (2D-2C) PIV.||Figure 11. View of two-dimensional, three-component (2D-3C) PIV experimental setup.|
|Figure 12. The Hydraulics Laboratories Litron LPY laser for TPIV|
The Laboratory has a new state-of-the-art lab office designed as a collaboration and modeling space for the lab personnel. The second floor includes an advanced computing center where experienced CFD specialists prepare computer simulations which are then sent to Argonne National Laboratory’s (ANL’s) Transportation Analysis Research Computing Center (TRACC), where multicore clusters run the simulations. A conference room for collaborative discussions is also on the second floor. The first floor of the office consists of an Advanced Engineering Hub for lab personnel to perform calculations and work immersed in the lab environment with noise and climate control to optimize performance. Multiple 3D printers are located both on the first and second floors of the office. These printers are utilized to create bridge models, sensor mounts, presentation models, and other essential functions.
|Figure 13. Lab conference room with Fortus 3D printer in far-left corner|
|Figure 14. Advanced Computing Center.|
|Figure 15. Advanced Engineering Hub.|
The Laboratory also has its own machine shop where various tools can be accessed. Basic tools such as Allen wrenches, pliers, fasteners, screws, etc., are stored here. Additionally, the machine shop is equipped with multiple milling machines and various saws that can be utilized to prepare experiments and build structures. A new addition to the machine shop is a state-of-the-art laser cutter that is being used to help prepare bridge models as well as precisely resized and shape compatible materials.
|Figure 16. Laboratory Machine Shop.|
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Turner-Fairbank Highway Research Center
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