New method for assessing lateral distribution of energy gradient in curved channels

Abstract

The energy gradient is a fundamental physical quantity of flow motion. To date, many studies have concentrated on uniform flow or fully developed curved flow, with the energy gradient approximated as the bed slope. This paper presents a new method to assess the lateral distribution of the apparent energy gradient in curved channels when curved flow is not fully developed. A dimensionless apparent energy gradient (K) is presented. An expression for K is explicitly formulated based on the Reynolds-averaged Navier–Stokes (RANS) equations and the lateral distribution of K is derived from measured velocity data. The method was applied in a 120° curved flume with asymmetric trapezoidal cross-sections. The results showed a bilinear distribution of K; that is, K remained nearly constant in the central region of the channel while, in the inner bank region, K increased linearly as the inner bank was approached. These results were derived for specific cases for curved channels with a side-slope, but the method for deriving K can be applied to other cases, thus providing a new way to study energy loss in curved channels to contribute to river management, such as estimation of discharge capacity and navigation improvement.