Hydraulic characterization of turbulent flow through and over a porous media

In order to calculate and predict the discharge through and over a porous media with turbulent flow, a series of experimental models of box gabion weirs were tested consists of aggregates with four mean diameters. Gabion models with four gabion lengths were selected, and experiments were performed in relatively large-scale flume with a width of 1200 mm. The coefficient of discharge was determined in free flow condition for box gabion weirs and in both through and overflow conditions. The discharge reduction factors of box gabion weirs were obtained and empirical equations were proposed based on non-dimensional parameters for through flow condition and for different submergence ratios. In overflow condition, the Darcy Weisbach's index was calculated for different aggregate mean diameters for box gabion weirs and for different gabion lengths. Furthermore, the interaction factor between through and overflow regimes were calculated, and an equation was proposed based on non-linear regression technique to predict the impacts of the superposition condition for free and submerged flow conditions. Finally, using flow visualization, the flow regimes over box gabion weirs and for overflow condition was characterized based on the contributed hydraulic parameters. Four flow regimes named as Impinging Jet Regime (IJR), Surface Jump Regime (SJR), Surface Wave Regime (SWR), and Deeply Submerged Regime (DSR) were introduced for developed flows in overflow condition. The results indicated that for lower submergence ratio, the IJR regime was similar to the flow regime in sharp-crested weirs; however, as submergence ratio increased, the distances among the SJR, SWR, and DSR, were diminished with the same regimes over the sharp-crested weirs.