عنوان مقاله [English]
Due to space constraints any access to a buried sewer conduit is seriously limited. In order to install the flow measurement devices, the space of manholes are the most appropriate places in a conduit. The conventional weir plates or sluice gates are usually used for flow measurements, however, these devices due to the nature of sewage, which contains sediments or floating objects are not suitable for flow measurements in sewer conduits. In a sewer conduit, the heavy solid particles tend to settle down behind a weir plate and floating objects accumulate behind a sluice gate, which both affects the accuracy of measurements by these devices. Therefore, the implementation of a combined system of weir-sluice gate at a cross section of conduit seems to be able to recover the defects of weirs and sluice gates. The application of this device in a circular cross section has not been received enough attention in the past. In the present paper the experimental results obtained from discharge measurement using combined weir-sluice gate system which allows simultaneously flow over and under a weir plate installed at the end of a sewer conduit are presented. The relationship between the experimental results and the theoretical flow which is a function of some geometric and hydraulic information of flow, are analyzed. Using statistical analysis of the obtained results of flow measurements accompanied with linear regression, an equation for discharge coefficient is proposed. The efficiency of the proposed technique is high enough that the associated error is limited to 10%.