Bonnabel & Duncan Pump Stations
In response to hurricane Katrina, the US Army Corps of Engineers decided to increase the frontal protection on four pump stations in the greater New Orleans area. Two of the pump stations (Bonnabel and Duncan) required the construction of wave breaks in Lake Pontchartrain as well as additional frontal protection in the form a T-walls. ALDEN provided wave break design assistance and analysis for using Computational Fluid Dynamics (CFD) tools to evaluate wave break performance. Hydraulic performance of the discharge flow with wave breaks and extended discharge due to the T-wall installation was confirmed with physical hydraulic models.
3-D CFD was used to evaluate the effectiveness of several different wave break designs for reducing the height of the wave impacting the front of the pump station. The wave spectrum used at the model boundaries was derived from the ADCIRC model. Model results were used to improve the wave break design with the objective of minimizing the structure length and maximizing wave height reduction. The models were also used to evaluate the potential impacts of the wave breaks on the erosion and deposition of sediment in the pump discharge canal. Modifications derived in the CFD models were evaluated in two 1:30 scale physical models for final design verification.
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Civil InfrastructureHydrology Hydraulics and Fluids
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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.