Laboratory Evaluation of Fine-mesh Traveling Screens for Protecting Larval Fish at Cooling Water Intake Structures

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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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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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