Investigation Emptying& Discharge Coefficient Function of Semi short through Shaft Spill way by considering Stepped barrel and vortex breaker on crest

Semi short through Shaft spillways are circlingSpillwaysused generallyfor emptying and evacuating unexpectedfloods on earth and concrete dams. There are different types of semi short through Shaft spillways: Stepped and Smooth ones.These spillways (Stepped spillways) pass more flow discharges through themselves in comparison to smooth spillways theoretically. Therefore, awareness of flow behavior of these Spillways, help using better and more efficiently. Moreover, using vortex breaker has great effect on passing Flow through semi short through Shaft Spillway. For using more efficiently, the risk of flow pressure decreases to less than fluid vapor pressure,called cavitations, should be prevented as far as possible. At this research, it has been tried to study Different behavior of Stepped chamber and different vortex shapes on spillway flow. From the viewpoint of the effects of flow regime changes on spillway, changes of step dimensions, and the change of type of Discharge will Studied Effectively. Therefore, two spillway models (one smooth spillway and one stepped spillway) with 3different Vortex breakers and threearrangements have been used to assess the Hydraulic Characteristics of flow. With regard to the inlet discharge to spillway, the parameters of pressure and flow velocity on spillway surface have been measured at several points and after each run. As a result , It has concluded that the best type of spillway with maximum discharge coefficient is smooth spillway with ogee shapes as vortex breaker and 3 number as arrangement and Finally emptying Discharge of different condition as function of Steps height, shapes of vortex breaker with higher Efficient arrangement and Submersible ratio are presented for better designing.