Page - 1068 - in Book of Full Papers - Symposium Hydro Engineering

Figure 8. Energy dissipation at 475 m3/s from the new spillway, with the existing spillway in the closed position. 3.5. REVISED DESIGN DURING CONSTRUCTION Later, during the construction of Långströmmen, the design needed to be revised due to issues such as poorer rock quality than expected as well as to excavate additional rock from the stilling basin to supply material for the reinforcement of the embankment dams. The well-known fact that CFD has difficulties in correctly modeling the complex flows in a stilling basin led to the construction of a physical models initially. However, as the physical model no longer existed, Computational Fluid Dynamic-modelling (CFD) was used to evaluate impacts of proposed changes designs. The CFD-model was only used for relative evaluation, by comparing qualitative results from different designs. First, the design preferred in the physical model tests was tested in the CFD-model and later compared with the design motivated by the requested changes in design [9]. Figure 9 and figure 10 show results from the CFD-modeling. 1068