Simulation of blockage efects on scouring downstream of box culverts under unsteady fow conditions

Scouring at the downstream of culvert is considered as one of the main reasons of culvert failure. Failure of the culvert structure is a catastrophic phenomenon. Studying the causes of scouring will give an idea about the solution probabilities; the blockage and geometry of culvert have a great infuence on the local scour. In this study, simulated results that are obtained from Flow-3D software of box culvert model and formation of scour at the outlet are compared with laboratory results of Sorourian to evaluate the accuracy of the numerical model. Laboratory box culvert was used at two conditions: the nonblocked situation and the partially blocked condition with the blockage ratio of 40%; for this destination, fner sediment was used in Sorourian’s study with the median grain size of 0.85 mm, and the fow conditions in the laboratory were unsteady. It means that the fow rates changed over a time period. The performance of the numerical model based on renormalization group is compared with experimental results. The comparison shows that the numerical results have a good agreement with experimental results