Numerical modeling of flow distribution and sediment transport for channel contractions

The main objective of this dissertation is to determine the flow distribution in channel contractions and to model the corresponding sediment transport. In channel contractions, the flow area is reduced, flow velocity is increased, and as a result the scour process is significantly increased. The intensity of local scour is amplified at locations where the velocity gradient is large. For the safety assessment of manmade hydraulic structures such as bridge abutments and coffer dam structures, the accurate assessment of scour problem is of great importance.; In the dissertation, first, using a numerical model, flow distributions at contracted reaches investigated. This model solves the Reynolds and continuity equations for fully developed turbulent flows. The hydrodynamic analysis investigates velocity and shear distributions in channel contractions due to the skewed abutments. Following series of numerical simulations, a semi-empirical equation was derived for expressing maximum velocity as a function of the contraction ratio, friction, and the skewness angle.; Next in the dissertation, a bed load transport model is developed for scour analysis in contracted reaches; this model is applied to estimate scour in the Mississippi River. A cofferdam was constructed to reduce the width of Mississippi by approximately 50%. Increases in flow velocities in the contracted region resulted in the significant lowering (erosion) of the channel bed. The numerical model solves the sediment continuity equation to investigate scour and deposition process in the vicinity of channel contractions. The proposed model is verified and its applicability is evaluated through the comparison with measured data.; Finally, the unsteady 2-dimensional convection and diffusion equation is solved numerically for the real-time simulation of suspended sediment propagation. By using the mixed boundary condition to express the external source terms or externally induced suspended load as a function of time in the algorithm, the model is capable of handling not only continuous load cases but also non-continuous suspended load influx. The suspended load transport model was verified using a case study for which an analytical exact solution is available and was applied to the real-time simulation of a suspended load influx case on the Mississippi River.