|Hawks Nest Spillway CFD Analysis|
CLIENT: Brookfield Renewable Power
Brookfield Renewable Power owns and operates Hawks Nest Hydroelectric on the New River in Fayette County, West Virginia. The Hawks Nest Dam and Spillway is approximately 836 feet long and is comprised of 14 ogee type spillway bays with flip buckets for energy dissipation. Each bay is equipped with spillway gates 50 feet wide by 25 feet high. Design discharge is 92,000 cfs. Brookfield agreed to incorporate hydrodynamic forces associated with spillway operations into the structural spillway stability analysis, which was conducted by HDR.
HDR retained NHC to conduct three-dimensional CFD modeling to compute the pressure distribution over two representative spillway sections (bays), for which two independent CFD models were developed. The pressure distribution over the surface of each bay was computed for five spillway discharge conditions, including the contraction effects of the piers as well as asymmetric gate operations.
The computed pressure distributions over the spillway were found to be highly non-hydrostatic and relatively complex. CFD model results indicated that potential locations of hydrodynamic uplift vary with gate opening and discharge. For small gate openings, the largest negative pressures on the spillway occurred at the section below the gate, where the Venturi effect of the gate contraction caused a local pressure drop. For large gate openings, the minimum pressure location moved farther downstream, where the water nappe experienced a tendency to detach from the spillway surface.