Effect of Opening Holes on the Hydraulic Performance For Crump Weir

Nowadays, developed and applied hydrology become very important thing in the life due to the wide verity advantages for the applications of this field. hydraulic structures such as crump weir are placed in channels to estimate or measure flow rate and flow control devices. in this study there is a new performance for crump weir which appears by adding opening holes in the model of crump weir. opening holes are working as an energy dissipater and as an improver for the discharge coefficient (cd). where the discharge coefficient (cd) is improved and recorded a higher values in comparison with conventional weir under the same laboratory conditions. the twenty-eight laboratory experiments were carried out using free flow in a horizontal channel of 12 m length, 0.5 m width and 0.35 m depth for a wide range of discharge. the experimental results indicated that cd values increase by increasing the number opening holes in body of crumb weir. thus; increasing the holes numbers from one to two and three holes) increase cd value about (10, 11 and 13%), respectively as compared with traditional weirs without opening holes. on the other hand, the results revealed better flow behaviour for two holes model than one and three holes, the flow is more stable and the transition flow regime has less instabilities and energy dissipation rate is the maximum. thus; the weir crumb with three voids are not stable and it was not easy to localized it in the channel.