Page - 1065 - in Book of Full Papers - Symposium Hydro Engineering

3. HYDRAULIC MODEL STUDIES For both spillways a physical model was constructed to assist in the detailed design of the waterways. The initial design of the models was supported by 2D computational hydraulic models to limit the scope of modeling necessary. 3.4. INITIAL HYDRAULIC MODEL LÅNGSTRÖMMEN: Prior to detailed design, hydraulic models have been constructed at Vattenfall’s hydraulic laboratory in Älvkarleby, Sweden (Yang et al. 2015). A 25 m long model, as shown in figure 5, was constructed at a scale of 1:60 with the objective of testing the following: 1. Impact of bathymetric features upstream that creates complex flow patterns during high floods. 2. The new spillway is situated some 350 m from the existing one with a small cross-section. This creates a velocity head that needed examination. 3. The flow behavior in the reservoir (point 1) and the head loss between the existing and new spillways (point 2) impacts the new spillway’s threshold and discharge capacity. 4. The energy dissipater design of the new spillway. Figure 5: Hydraulic model of Långströmmen dam, scale 1:60 One of the main tasks of the model was to determine the final threshold of the new spillway. The lower the threshold, the higher capacity but also increased velocities downstream which impacts riprap design. Existing Spillway New Spillway Embankment 4 1065