CS44B - Concurrent Session 44B: CFD and Physical Modeling of a Unique Glade Dam Spillway

Computational Fluid Dynamics (CFD) and physical hydraulic modeling were conducted to support the design and optimization of a unique spillway for the proposed 175-ft high Glade Dam and reservoir near Fort Collins, Colorado. The unique design includes a long upper spillway chute that traverses the right abutment and makes a 110-degree turn in the middle of the alignment and includes multiple structure transitions along the 2100-ft long spillway before discharging into the proposed reservoir forebay. The primary focus of this spillway modeling effort included the converging upper chute, the vertical drop to the 110-degree turn that transitions to a 350-ft long baffled apron chute, and the 950-ft stepped discharge channel.

Comprehensive CFD modeling was first conducted to develop the 110-degree transition to achieve the goals of subcritical flow and relatively uniform flow before entering the baffled apron chute, a general requirement for the baffled apron chute to achieve satisfactory performance according to USBR design guidance EM-25. Various floor depths and baffle arrangements in the 110-degree transition were modeled in CFD to guide the selection of a design that would meet the design criteria.

Due to the unique and complex nature of the design, a physical modeling study was conducted for the arrangement developed from CFD modeling to further investigate the hydraulics and look for opportunities to improve the hydraulics if needed. The physical model was also used to evaluate the hydraulic performances down the 350-ft long baffled apron chute, which was noted to have unsatisfactory hydraulics according to CFD simulations. The physical model was also used to assess the hydraulic characteristics at the end of the baffled apron chute to design the stepped discharge channel downstream. Lastly, the physical model was used to evaluate how debris could potentially affect the performance of the overall design, especially for the baffled apron chute.

This presentation will provide an overview of the spillway design development, the results from both the CFD and physical modeling, discuss how the two modeling methodologies complement each other and describe the iterative modeling effort incorporated to achieve the final design layout.