عنوان مقاله [English]
Experimental investigation on Afflux due to inclined circular bridge Pier
Afsaneh Nobakht1 , Masoud Ghodsian2 , Mojtaba Mehraein3
1- Master’s graduate in Water resources management,Tarbiat Modares University
2- Professor of Hydraulic, Water Engineering Research Center, Tarbiat Modares University, Tehran-Iran
3-Assistant Professor of Hydraulic Structures Kharazmi University, Tehran-Iran
Abstract: Piers and abutments cause local contraction in the rivers. As a result of the contraction, the water level increases in the upstream section of the bridge named as afflux. Afflux is one of the key concerns in the design of a bridge construction and the afflux estimation is important since the specific regions in the upstream of the bridge must be protected against the flood. Hence, the afflux estimation should be conducted for river training of the upstream sections, before bridge construction. In this research 54 experiments were conducted to investigate the effects of different parameters such as pier angle respect to vertical, flow Froude number and the contraction ratio on afflux. Design expert software is used to design the experiments and to analyze the results. According to the results, as the axis of the pier tend to the downstream and side walls of the channel the afflux increased. However, the afflux decreases as the pier axis deviated to the upstream. Also, the effect of inclination angle on afflux is smaller for inclined piers towards upstream than inclined pier to the downstream or side walls. By increasing the pier angle from zero to 24 degrees, toward channel side walls and downstream, the afflux increases 20 and 15 percent respectively. While in the same situation by increasing the pier angle from zero to 24 degrees, toward upstream the afflux decreases by 5 percent. The higher affluxes were observed in larger flow Froude numbers and contraction ratios. The analysis showed that the flow Froude number and contraction ratio have more effects on afflux as compare to other parameters. Finally, an appropriate equations are presented to estimate the afflux.
Key words: Afflux, Inclined pier, Design expert software, Froude number, Contraction ratio.