Three-dimensional hydrodynamic modeling of permeable and impermeable river training works using CCHE 3D model and laboratory experiments

Abstract

Protection of river banks is an inseparable part of river training works. Permeable and impermeable structures are most commonly used for riverbank protection. Porcupines impose a mild impact on the river by implementing its effect gradually. However, during high flow conditions, these structures are ineffective and often get washed away. On the other hand, impermeable spurs impose a sudden impact on the river system and drastically reduce the velocity in its zone of influence. Due to this, turbulence is generated near the nose of the structure leading to the formation of scour hole, which results in structural instability. Therefore, an attempt has been made to study the effectiveness of the interventions mentioned above in stabilizing and protecting the rivers. Due to several limitations of the physical models, such as scale effect, steady-state flow, and high cost, which make it difficult to carry out in the case of a braided river system, a three-dimensional hydrodynamic model was used. In this study, the performance of the 3D hydrodynamic model CCHE 3D is evaluated in terms of velocity reduction potential by comparing it with experimental results. It was observed that initially, the velocity was in the range of 0.1 m/s under emergent condition, which reduced by more than 50% in the downstream of single porcupine screen, more than 75% in the downstream of two porcupine screens, and more than 94.36% in case of geobag layout. Flow deflection was also observed, but it was not significant.