Tarrant Regional Water District Integrated Pipeline Project
Alden designed, constructed and tested a ~1:7 Froude scale physical hydraulic model to evaluate the hydraulic performance of the Tarrant Regional Water District Integrated Pipeline Project Joint Cedar Creek Pump Station in accordance with the Hydraulic Institute Standards (HIS).
The pump station consists of six 66 inch tee screens and 7 vertical pumps, each with a rated capacity of 27 to 49.4 million gallons per day (mgd). The maximum total flow for the pump station is 277 mgd, which corresponds to all seven pumps operating. The design requires each of the seven pumps to be placed into a depressed pump can located in the wet well floor.
Work Performed
Baseline tests were conducted to evaluate the pump hydraulic performance in terms of vortex formation, swirl at the pump impeller, and the velocity distribution approaching the pump impeller. The tests were conducted at two water levels; the normal water surface elevation and the maximum pool elevation. The test results identified the presence of unacceptable dye cAre subsurface vortices emanating from the can walls.
Two design modifications were developed and evaluated each of which met the HIS acceptance criteria. The first design modification included can-wall roughness vanes at 10 degree intervals to dissipate the unacceptable vortices. The second design modification included an inverted torus dish installed on the can floor (under the pump suction) as well as shortening the existing vertical can vanes. The dish modification was selected as the preferred modification since it demonstrated the most streamlined flow entering the pump.
Project Highlights
- Baseline design was an innovative combination of a traditional wet well configuration with recessed pump suction cans to minimize overall excavation costs.
- Two design modifications were provided to the client that satisfied the HIS acceptance criteria and the most cost-effective design was selected.
Capability
Civil InfrastructureServices
Hydropower Field ServicesRelated Projects
An existing roof vent arrangement was allowing rainwater to enter the Pot Room. Alden supported efforts to develop a roof vent geometry to eliminate the intrusion of rain water. The purpose of the CFD study was to ensure that the roof vent modification did not increase pot room temperature levels beyond specified limits for workers in the plant.
To evaluate the existing and proposed Pot Room arrangements, thermal and fluid flow profiles in the immediate vicinity of the pots were determined based on air flows through the plant floor and wall mounted vents. The detailed CFD model was developed from plant drawings to include all major basement, pot room and roof venting geometries. The surrounding ambient environment was included with quiescent atmospheric conditions and average ambient temperature. Thermal losses form the pots to the pot room air and from the pot room to the environment were included in the analysis. The results of the CFD modeling showed that the proposed modification to the roof venting arrangement was acceptable and would not increase the temperature in the worker-occupied spaces by more than 2 degrees F.
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Civil Infrastructure
Smelter Pot Room Roof Ventilation System
Read how a CFD study ensured that a roof vent modification did not increase pot room temperature levels beyond safe levels
Plant McDonough, owned and operated by Southern Company, has experienced excessive siltation at the makeup water intake. The intake uses cylindrical wedgewire screening within an intake originally designed for much larger, once-through cooling water flows. Flow modeling was performed to provide a viable passive solution to reducing the sediment accumulation at the intake. To model the geometric details of the system accurately, a field survey was performed prior to the flow modeling efforts. The flow study included both CFD modeling and scale physical modeling.
For this investigation, Alden developed a 1:20 scale live bed physical model. This model was extremely well tuned to reproduce the behavior of bed load sediment. Even with the very fine crushed walnut shell particles, however, it was challenging to reproduce the behavior of suspended load. The use of a high fidelity CFD model, therefore, proved extremely useful for this project, in that suspended load is generally very accurately tracked with CFD models, which are not well validated for bed load simulation. By using the two together, the two extremes of sediment transport are captured, and developing a solution that covers this range has a high likelihood of success.
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Civil Infrastructure | Hydrology Hydraulics and Fluids
Plant McDonough Intake Modification
CFD and physical model study to assist in the evaluation of a solution to reduce the sediment accumulation.