عنوان مقاله [English]
The Present study introduces the slit and solid semicircular flap plates for flow measurement in horizontal open circular canals under free flow conditions. This structure consists of a semicircular plate which is installed and hinged from its diameter along a circular canal. The deviation generated by the water flow on the plate is a function of hydraulic characteristics of flow, the geometry of the structure and flow discharge. This simple measuring structure is portable and can easily be installed in circular canals and be used with acceptable precision. In this study, based on the theoretical and experimental studies of the passing flow through the semicircular flap plate, some equations were developed for estimating the flow in circular canals via the dimensionless discharge-critical depth relation. In order to calibrate the proposed equations, the laboratory data were collected and used. In addition, to estimate the passing flow through the flap plate, an explicit relationship was developed to compute the dimensionless critical depth and discharge. The dimensionless critical depth-discharge method used in this study is able to estimate the flow discharge through the semicircular plates with an average error of 3%. Due to the low average errors of the proposed discharge equations for the semicircular flap plate (an average error of 3.6% without considering the Reynolds number and an average error of 3% by considering the Reynolds number), this structure is suggested as a discharge measuring structure in circular open canals.