جستجوی مقالات مرتبط با کلیدواژه « momentum » در نشریات گروه « عمران »

The researchers tried to build gabion barriers by considering the materials around the dam. In this study, gabion barriers with applicability were used, in which trapezoidal barriers were made using metal mesh and these barriers were filled with sand grains with an average size of 0.5 cm. The reason for using these dimensions of aggregate was the presence of stones with dimensions of 0.5 meters in nature, and if the laboratory results are suitable, it is possible to use them in the implementation, while proper slope. According to the executive criteria, it was considered to build the sides of the barrier in order to evaluate the possibility of falling aggregates. In this design, an attempt has been made to investigate the effect of gabion barriers on the percentage reduction of flow head flow. To better understand their efficiency in different conditions, some important parameters such as concentration, inlet discharge, slope and height of barriers have been considered.

One of the most important problems in open channel flow is determination of shear stress. It is difficult to determine boundary shear distributions in real life applications. Laboratory flume studies have still been serving to deal with this problem. This study is focused on experimental measurement of the bed and wall shear stresses as well as estimation of hydraulic resistance coefficient for flow in rectangular open channels. The energy and momentum approaches were used to determine contribution of wall and bed shear forces on total boundary shear. The hydraulic grade line was measured using an indirect method while a frictionless system (knife edge flume) was used for the momentum measurements. The local boundary shear stress was measured using a 4-mm diameter Preston tube connected to a differential pressure transducer and a data acquisition system. The calibration curves proposed by Patel were used to convert pressure reading to shear stress. The results were adjusted by the total shear force calculated from the energy and momentum methods. A nonlinear regression-based technique was carried out to develop equations and to determine the percentage of wall and bed shear stresses on the wetted perimeter of a smooth rectangular open channel. Comparison of results for shear stress measurement by direct and indirect methods shows maximum errors of 4 and 8 percent respectively.