Effects of length, height and spacing of grouped spur dikes on upstream water levels in an open channel

Spur dikes are flow regulators used in a wide range of streams and open channels. Recognizing the site-specific nature of their design, this study experimentally and numerically investigated the impact of spur dike height, length, and spacing on upstream water levels within a sediment-free open channel. Reynolds-averaged Navier-Stokes (RANS) equations and the renormalization group (RNG) k-ε turbulence model are used for the numerical analysis. Contrary to classical one-sided spur settlements existing in the literature where height primarily causes localized effects with minimal upstream impact, the configurations examined in this study led to a significant increase in upstream water levels, especially as the spur length-to-channel width ratio (l/B) increased. The findings showed that the length of the spurs also causes significant changes in the upstream water level for large discharges. The analysis indicated that spur length, alongside height, can elevate the upstream water levels by up to 350% at low Froude numbers, depending on its placement within the channel. Notably, the spacing between spurs exhibited the least influence on upstream water levels; increasing this distance resulted in a reduction of the upstream water level and induced secondary flow formation in the inter-spur regions. These results highlight the importance of considering spur length when designing these flow regulators, especially in scenarios where upstream water level management is the primary objective. The findings offer valuable guidance to engineers on how to optimize the geometric configuration of grouped spur dikes to effectively regulate flow under different hydraulic conditions. The results also provide practical insights for developing design strategies that balance water level control, flow stability, and channel conveyance efficiency in river engineering applications.