مدل رياضي پيش بيني فرسايش كناري در پيچانرودها

Developing A Two Dimensional Mathematical Model For Predicting Lateral Erosion In Meandering River

in this research using finite volume method a two dimensional mathematical model is developed for predicting the changes of river morphology. The developed computer package can be used specially for calculating bank erosion and sedimentation in meander loops. In the prepared model first by solving the energy, velocity diffusion and momentum equations, flow parameters including main and secondary velocities, main and secondary shear stresses and critical velocity and shear stresses are determined. Then by comparing the critical flow velocity with the longitudinal flow velocity, the rates of sediment transport in longitudinal direction for each sub-section are computed. The transversally sedimentation (or erosion) rate is calculated, afterwards, through comparing the calculating bed shear stresses in the two main directions, together with determined sediment exchange among the subsections based on mass continuity equations. In this manner, the erodibilty parameter is calculated for each river section and by using periodic wave model the river plan changes is predicted. This investigation has indicated that: - The most suitable grid for dissolving the equations is 50*20 grid. - The finite volume method can be suitably used for analysis of natural river morphology problems. - To dissolve the questions, the point-by-point method, in spite of its simplicity, has shown a more suitable accuracy. -The best numerical methods for dissolving the equations (least time, accuracy of answer) are point-by-point (PBP) and line-by-line up to down (LBLUTD) methods, respectively. -Ghezel-Ouzan River has a parabolic velocity distribution and the exponent of the suggested equation varies between 3 to 8. - The maximum displacement of Ghezel Ouzan River is different in various places and it depends on discharge and slope. The prepared model is very sensitive to the variation of discharge and slope.