Study on Spacing Threshold of Nonsubmerged Spur Dikes with Alternate Layout

Abstract

This paper investigated the spacing threshold of nonsubmerged spur dikes with alternate layout to classify the impact scale of spur dikes. A mathematical model was built based on standard $k$-$\epsilon$ model, finite volume method (FVM), and rigid lid assumption and was verified by experimental data. According to dimensional analysis, three indices, that is, $F_r$ (Froude number), $B/b$ (channel width to dike length), and $B/h$ (channel width to water depth), were identified as the influencing factors on the spacing threshold, based on which fifteen sets of conditions were simulated. The calculation results indicate that $B/h$ is the most influencing parameter on $S_c/b$ (spacing threshold to dike length), followed by $B/b$ and $F_r$. A dimensionless empirical formula of spacing threshold is fitted by multivariate regression. The results of four sets of additional conditions illustrate that the generalization of empirical formula is satisfactory and the precision of interpolation is higher than that of extrapolation. Furthermore, the spacing threshold of alternate spur dikes is generally smaller than ipsilateral spur dikes.