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This is the first attempt to study the effect of debris on the scour at side by side pier and abutment. A large set of experimental tests was carried out at the hydraulic laboratory of Shahid Bahonar University of Kerman, in a tilting flume with 10 m length, 0.8 m width and 0.5 m depth. Effect of debris shape, thickness, position, length, and the distance between abutment and pier was investigated. Results revealed that the main factor in deepening and developing of scour hole is the distance between pier and abutment, lp, by increasing the distance, the scour depth primarily increases and then decreases to eventually reach the scour depth at single pier. The observations indicated the significant effect of debris on dimensions of scour hole, for example, increasing the debris thickness and length increased the maximum scour depth up to 30 and 8%, respectively. Based on the measured data, some improvements were made on the existing equations and a set of new relations was presented to estimate the side by side pier and abutment scour depth. Flow and scour pattern at side by side pier and abutment were investigated. Effect of debris accumulation on the scour processes was studied. Based on the measured data, improvements were made on the previous equations. New relations were proposed to predict side by side pier-abutment scour depth. [ABSTRACT FROM AUTHOR]

Local scouring is a leading cause of bridge collapses. To protect bridges against local scouring, different countermeasures have been proposed and tested in the literature. In this study, the performance of collars was evaluated for scour reduction at two tandem piers aligned with four skew angles ( θ) of 0 ° , 30 ° , 60 ° , 90 ° with respect to flow direction. For this purpose, long duration tests were conducted with uniform sediments under clear-water conditions with flow intensities close to the threshold of sediment motion. The results showed that increasing the skew angle increased the scour depth, while the performance of collars for scour reduction decreased. The maximum and minimum scour depths occurred at skew angles of θ = 60 ° and θ = 0 ° , respectively, around both the piers with and without collars. Analysis of the results indicated that the maximum scour depth at the upstream pier shifted to the downstream pier from θ ≥ 20 ° and θ ≥ 28 ° for the tandem piers with and without collars, respectively. In addition, as the skew angle increased, the equilibrium time of scour increased. Moreover, the performance of collars for scour reduction around the piers decreased over time. [ABSTRACT FROM AUTHOR]

Normal depth is an important parameter for the design of channels and canals. For rectangular, trapezoidal, and circular channel sections it is possible to express normal depth by a trial-and-error procedure or analytically. However, the effects of free-surface on the design charts for determination of the normal depth are not investigated. In this paper, graphical solutions of normal depth for the rectangular, trapezoidal, and circular cross-sections have been obtained in the non-dimensional form. To evaluate the resistance effects of the free-surface in the calculation of the normal depth, the dimensionless-form of Manning's equation with free-surface weight factor is introduced herein. The design charts reported previously were modified. [ABSTRACT FROM AUTHOR]

In this paper, a multi-grid algorithm is applied to a large-scale block matrix that is produced from a Beam and Warming scheme. The Beam and Warming scheme is used in the simulation of unsteady flow in an open channel. The Gauss-Seidel block-wise iteration method is used for a smoothing process with a few iterations. It is also shown that the governing equations determine the type of prolongation and restriction operators for the multi-grid algorithm. [ABSTRACT FROM AUTHOR]

Abstract: Applications of the proposed model by Maghrebi which is able to predict the isovel contours quantitatively in a section of an open or closed channel both with irregular shapes and roughness, have been presented [Maghrebi MF, Rahimpour M. A simple model for estimation of dimensionless isovel contours in open-channels. Flow Meas Instrum 2005;16(6):347–52]. In the present paper, the model is applied to a flume with a composite roughness as well as to rivers with irregular cross section geometries. The obtained isovel contours in a flume section with nine cases of composite roughnesses are used for discharge estimations. Then, they are compared with measured ones. Model predictions are well correlated with the measured data. The isovel contours obtained by applications of the model to river sections are used to estimate the depth-average and surface velocities. Then they are compared with the measured data at the corresponding sections. The predicted results of water surface velocities are in good agreement with the measured data in a cross section of the River Unon in Japan. The result of the depth-average velocity shows, even better agreement with the measured data as well as the best analytical results for the River Severn in the UK. [Copyright &y& Elsevier]