Hydraulic experiment for equivalent resistance coefficient for inundation simulation model

Abstract

The equivalent resistance coefficient including the effect of drag caused by obstructions as well as a bottom roughness was investigated. The equivalent resistance coefficient can be utilized for inundation simulations that use relatively larger grids as applying the coefficient into the bottom friction term in the shallow water equation model. In order to investigate the equivalent resistance coefficient, the hydraulic experiment was performed with unsubmerged square piers in an open channel. The piers were arranged with an equal interval along longitudinal and transverse directions, and the water depth of a mean uniform flow was measured for various discharges. The equivalent resistance coefficient n-value was evaluated by applying the measured data to the Manning's equation. A coefficient implicating the interaction effect of piers' drag was estimated based on the experimental results. And as including this drag interaction coefficient a semi-analytical formula of the equivalent resistance coefficient was derived from momentum analysis. The semi-analytical formula was compared with the experimental results. From the comparisons it was found that when the unsubmerged piers were aligned in open channel, the equivalent resistance coefficient was strongly dependent on the interval of piers, and the n-value increased nonlinearly with the water depth. © 2010 World Scientific Publishing Co. Pte. Ltd.