Experimental study on flow over arced-plan porous weirs

Abstract

Unlike conventional impermeable weirs, porous weirs do not clog the flow and passage of aquatic life with increased aeration or aerobic reactions. They have minimal negative effects on the environment and are known as environmentally friendly structures. This study experimentally investigates the hydraulic performance of arced-plan porous weirs (APPWs) in different hydraulic and geometric conditions. For this purpose, four different porous and two solid weirs were examined. Experiments were conducted in a horizontal laboratory flume with length, width and height of 20, 0.6 and 0.5 m, respectively, for a wide range of flow rates, particle sizes and three arc lengths. Results showed that increasing filling material sizes increases the free discharge coefficient and reduces the submerged discharge reduction factor (DRF). It was also concluded that the weirs’ effective length significantly impacts the free discharge coefficient and has no significant effect on the threshold submergence index and submerged DRF. Unlike solid weirs, the threshold submergence of porous weirs occurs at a downstream depth lower than the weir's height. Finally, according to the dimensional analysis and gene-expression programming approach, three relations were extracted to calculate the free discharge coefficient, threshold submergence index and submerged DRF for APPWs. HIGHLIGHTS Analyze the hydraulic performance of the arced-plan porous weirs for different hydraulic and geometrical conditions.; Determine the boundary between modular and non-modular flow.; Develop new equations for discharge coefficient in free flow, modular limit index and discharge reduction factor in submerged flow.; Investigate the effect of weir direction on the hydraulic performance of arced-plan porous weirs.;

Keywords

• arced-plan porous weir
• discharge coefficient
• discharge reduction factor
• gene-expression programming
• threshold submergence index