Performance Evaluation of Energy Dissipation in Spillway Chute Blocks Using a Calibrated Flow-3D Numerical Model

Spillways are among the most critical hydraulic structures, Chutes spillways are frequently used, in which the flow is characterized by high velocities, pressure fluctuations, and intense turbulence (Chanson, 2022). If the kinetic energy of current is not adequately dissipated, the structure becomes susceptible to serious hydraulic and structural problems such as bed scour, bank erosion, and cavitation damage, which affects the stability of the entire system (Falvey, 1990). Accordingly, energy-dissipating elements such as blocks installed on the chute surface which promote recirculation zones, flow separation, and secondary vortices, provide an effective means of disrupting high-velocity flow (Scheres et al., 2020). In this study, the hydraulic performance of chute blocks was investigated using FLOW-3D software.

The numerical model was validated, by the reference experimental data for a unit discharge of 60 cfs/ft (USBR, 1984). Comparison of the numerical and experimental results for water surface elevation at 132 computational points along the chute showed a mean absolute percentage error (MAPE) of approximately 5%. Other parameters, including pressure distribution, longitudinal velocity component (Ux), turbulent kinetic energy (k), turbulence intensity, turbulent dissipation rate (ε), Froude number, and total hydraulic head were extracted and analyzed. Following validation, three modified chute-block geometries, namely Curve, Plus, and Cross, were evaluated under identical hydraulic conditions.

To compare the performance of different geometries, pressure, flow velocity, free-surface elevation, flow depth, turbulent kinetic energy, turbulence intensity, turbulent dissipation rate along chute, Froude number, and total hydraulic head were extracted and analyzed at three control sections. The results indicated the block geometry significantly affects the flow behavior and the degree of energy dissipation. Among the geometries examined, the Curve model exhibited the most stable and favorable hydraulic performance, producing the most desirable reductions in velocity, pressure, Froude number, and total hydraulic head across most of the evaluation indices. This geometry also promoted a more uniform turbulence distribution and prevented rapid velocity recovery downstream. Furthermore, Curve model requires less construction material and is therefore more economical. The findings demonstrate that CFD modeling can serve as an efficient tool for evaluating and optimizing the geometry of spillway energy dissipators prior to physical implementation.