Laboratory Evaluation of Fine-mesh Traveling Screens for Protecting Larval Fish at Cooling Water Intake Structures
The main objective of the study was to determine the post-collection survival of larval fish when exposed to compounding stresses of screen impingement and transfer. In particular, the project sought to determine the effects of water velocity and duration of impingement on survival. This was a multi-year, multi-phase study that included small-scale, tabletop testing along with large-scale prototype testing involving multiple species.
Survival was evaluated for impingement and entrainment of larval fish of differing sizes and species. Initial testing was done in smaller, tabletop test flumes to allow extensive replication and to help in the selection of test conditions and variables to be used in the large flume testing. Testing was then moved to a large scale flume, using three different prototypes of traveling screens. Collection efficiency and survival rates were measured for different species, fish sizes, and flow velocities.
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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.