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چکیده
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Presence of strong secondary currents and their interaction with the topography of the channel bed in river bends have significant effects on the distribution of longitudinal and transverse velocity and consequently the shear stress across the width and length of bend. Flow in river bends has been investigated by several researchers, and a variety of different equations for identifying the parameters of flow have been proposed. However, the proposed equations do not provide a good solution; this is especially the case in sharp bends in which the strong secondary flow influences the velocity pattern. In this paper, first, some models for identifying longitudinal velocity profile will be presented and be compared. Then, taking the properties of longitudinal velocity in sharp bends into consideration, a new model for computing the velocity will be proposed. The channel under experiment was located in the laboratory of hydraulics department of EPFL University in Switzerland, with curve radius of 1.7m from the centerline, 1.3m width, and 193 degree of central angle. The experiments in this channel were undertaken with discharges of 63, 89, and 104 l/s on a developed topography. The results achieved from the study showed that Kikawa’s model, among all the proposed models for predicting longitudinal velocity, is more compatible with laboratory data. Furthermore, the new model not only has the properties of a longitudinal velocity in sharp bends but also enjoys less error than the other models.
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