Evaluations of potential blade-strike on an axial-flow marine hydrokinetic (MHK) turbine were conducted using a method that integrates the following components into a computational fluid dynamics (CFD) model: (i) advanced eddy-resolving flow simulations, (ii) inflow turbulence based on field data, (iii) moving turbine blades in a transient flow, and (iv) Lagrangian particles to represent fish. The sensitivity of blade-strike probability to the following conditions was also evaluated: (i) turbulent environment, (ii) fish particle size and (iii) mean stream flow velocity. A limitation of the method is that fish are represented as particles that simply move with the fluid and can exhibit no behavioral response such as avoidance of the MHK turbine. This limitation causes a tendency for the model to overestimate strikes since it is likely that some fraction of an approaching population of fish would actively avoid the turbine.The CFD-based blade strike simulations provide not only the frequency of collisions, but also insights into the causal relationships between the flow environment and resulting particle strikes on rotating blades. The results were compared against the outcomes of a conventional method that only considers the kinematic aspects of the fish passage event without any regard for the flow dynamics. Overall, the conventional method, while simple to apply, largely overestimates the probability of strike, and lacks the ability to produce potential fish and aquatic biota trajectories as they interact with the rotating turbine. In contrast the CFD-based Lagrangian method utilizes a set of experimental correlations of exposure-response of live fish colliding on moving blades, frequency of occurrence, intensity of the particle collisions to calculate the estimated survival rate of fish encountering the MHK turbine. Estimated survival rates were greater than 96%, which are comparable to or better than many conventional hydropower turbines. Although the proposed CFD framework is computationally more expensive, it provides the advantage of evaluating multiple mechanisms of stress and injury of hydrokinetic turbine devices on fish and relating those to specific design features of the MHK turbine.iii

Although 400 cubic yards of rocks were removed from the stilling basin, there are still large volumes of rock downstream of the apron that could, under certain flow conditions, move upstream into the stilling basin. CENWP is investigating operational changes that could be implemented to minimize future movement of rock into the stilling basin. A key analysis tool to develop these operational changes is a computational fluid dynamics (CFD) model of the spillway.A free-surface CFD model of the Bonneville spillway tailrace was developed and applied for four discharge scenarios. These scenarios looked at the impact of discharge volume and distribution on tailrace hydraulics. The simulation results showed that areas of upstream flow existed near the river bed downstream of the apron, on the apron, and within the stilling basin for all discharges. For spill discharges of 300 kcfs, the cross-stream and downstream extent of the recirculation zones along Cascade and Bradford islands was very dependent on the spill pattern. The center-loaded pattern had much larger recirculation zones than the flat or bi-modal pattern. The lower discharge (200 kcfs) with a flat pattern had a very large recirculation zone that extended halfway across the channel near the river bed.A single scenario (300 kcfs of discharge in a relatively flat spill pattern) was further interrogated using Lagrangian particle tracking. The tracked particles (with size and mass) showed the upstream movement of sediments onto the concrete apron and against the vertical wall between the apron and the stilling basin from seed locations downstream of the apron and on the apron.iii