Author(s): Obasi Lazarus Nwosu; Agunwamba Jona Chukwuemeka
Linked Author(s):
Keywords: Channel bifurcation; Convex section; Flow rates; Off-take angles; Suspended sediment
Abstract: A model of river channel was constructed and used to investigate the effect of off-take angles on suspended sediment distribution at convex channel bifurcation. Different off-take angles of sizes 15o, 300, 450, 600, 70o, 80o and 900 with varied main channel flow rates were used for the study. Predicting equations dependent on parameters such as off-take angles, channel discharges and dispersion coefficients were developed and the relationship shows that the sediment distribution ratios are inversely proportional to the specific discharge ratios, off-take angles and proportional to the dispersion coefficient. Results of the study indicate equally that even with constant main channel discharge, the off-take channel sediment intake increased significantly with higher off-take angles. However, it was observed that the predicting equation over estimated the off-take channel sediment yield for bifurcation angles between 15o – 72o and for those between 76o - 90o the sediment values were under estimated for most of the main channel flow rates. The predicted sediment values equaled the experimental values at the off-take angles of 40o – 74o but varied differently for each of the main channel flow rates except for those of Q19 that were entirely under estimated. It could be seen from the various off-take angles that the divergence in results obtained from the experimental works and predicting equation is in the range of 3. 03% - 21. 05% for minimum main channel flow rate and 4% - 19. 75% for maximum main channel flow rate. This suggests that the predicting equation could be useful in the evaluation of sediment yield at convex channel bifurcation. Conversely, the general observation from the study is that intakes at convex channel bifurcation would attract more sediment material from the main channel even at small off-take angles thereby requiring constant desilting of deposited materials.
Year: 2013