Fixed-Cone valves are often used to dissipate energy and regulate flow at the low level outlet works of dams. Fixed-Cone valves, also known as Howell-Bunger valves, create an expanding conical jet allowing the energy of the water to dissipate over a large area. However, in many applications constructing the large stilling basin necessary for these valves is either not possible or not feasible. In order to reduce the relative size of the stilling basin, hoods or concrete containment structures have been used in conjunction with Fixed-Cone valves. This paper compares two methods of energy dissipation used in conjunction with concrete containment structures. The first method of energy dissipation is the use of baffles, and the second is a deflector ring with end sill. In order to determine which type of energy dissipation method was most effective for this particular application, measurements and observations were taken in order to compare the amount of energy dissipated by the structure and the Fixed-Cone valve, the air demand of the structure, the velocities downstream of the structure, and flow stability downstream of the structure. This information will be useful to engineers allowing them to minimize scour and erosion associated with concrete containment structures.
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