Effects of the gap on the local scour around two tandem piles in shallow flows

Local scour around two tandem piles in shallow water is numerically investigated under clear-water conditions. The characteristics of the scour process, depth, and flow fields are shown to be significantly influenced by the pile gap ratio (G/D = 1.0-5.0) and water depth ratio (h/D = 0.5-3.0). Under the same G/D, the dimension of the scour hole and the maximum scour depth around two piles become larger with the increase of h/D. Under the shallowest water depth condition (h/D = 0.5), the scour dimension and maximum scour depth of the rear pile are larger than that of the front pile, due to the weak upflow and strong downflow upstream of the rear pile. However, under the deepest water depth condition (h/D = 3.0), the scour hole becomes smaller than that of the front pile, due to the significant upflow downstream the front pile by less confinement from the high water surface. The vortex shedding patterns and their interaction with the sediment transport in different G/D and h/D cases are also discussed.

Automated summary

Local scour around two tandem piles in shallow water was numerically investigated, and the results showed that the scour process, depth, and flow fields were significantly influenced by the pile gap ratio and water depth ratio. Increasing the water depth ratio led to larger scour dimensions and maximum scour depths, and the scour patterns differed between the front and rear piles under different water depth conditions.