نوع مقاله : مقاله پژوهشی
نویسندگان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Due to importance of scouring, numerous researchers have investigated the local scouring and various methods suggested for controlling this phenomenon. These methods can be divided into two general categories, increasing the bed resistance and changing the flow pattern. The collars are plates which installed parallel to the bed on the pier; operate as an obstacle against the down flow and prevent the formation of the scour hole at the upstream side of the pier. The current research investigated the effect of elliptical collar on scouring process. For this purpose, three elliptical collars with the ratio of the collar length at the downstream of the pier to the pier diameter ( ) of 1, 1.5, 2, the 3 mm thickness and cylindrical pier with 21 mm diameter, were examined at 5 different discharges. Also, the Length, width and depth of the laboratory flume were 8, 0.255 and 0.3 meters, respectively, and the mean size of the bed sediment was 0.88 mm. The results showed that utilizing the collar led to reduce the scour volume in comparison with the usage of the pier without collar. The maximum (81.5%) and minimum (13.36%) scour reduction were belonged to the elliptical collars with and , at Froude numbers of 0.246 and 0.294, respectively.
کلیدواژهها [English]
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