FLOW DISTRIBUTION IN MEANDERING COMPOUND CHANNEL

Abstract

ABSTRACT When the flows in natural or man made channel sections exceed the main channel depth, the adjoining floodplains become inundated and carry part of the river discharge. Due to different hydraulic conditions prevailing in the river and floodplain of a compound channel, the mean velocity in the main channel and in the floodplain are different. This leads to the transfer of momentum between the main channel water and that of the floodplain making the flow structure more complex. Reliable estimates of discharge capacity and its distribution for a compound channel are essential for the design, operation, and maintenance of open channels, more importantly for the prediction of flood and flood protection measures. Results of some experiments concerning the velocity and flow distribution in meandering and straight compound channels are presented. Discharge distribution in such compound channels is strongly dependant on the interaction between flow in the main channel and that in the floodplain. The influence of the geometry on velocity, flow distribution, and the different functional relationships are obtained. Dimensionless parameters are used to form equations representing the flow distribution between main channel and flood plain subsections. A set of meandering and straight compound sections of rectangular and trapezoidal cross section is studied with width ratio varying between 2 to 16.08. The equations agree well with experimental discharge data. Using the proposed area method, the error between the measured and calculated discharge distribution for the meandering and straight compound sections is found to be the minimum when compared with that using other investigators.