Abstract
An analytical model is proposed to determine the discharge capacity in a meandering compound channel. The channel cross-section is divided into four sub-sections, such as the lower main channel, the floodplain within the meander belt and the two outer floodplains. Momentum transfer in-between these four subsections is taken into consideration in the analytical model. The model basically determines the force balance of each individual subsection to predict its mean velocity and thereby the sub-sectional discharge. The paper suggests a non-dimensional parameter, αT, which is the momentum transfer coefficient, that is determined to be unique for each individual channel. The paper deals with the calibration of this parameter for both largescale and small-scale data sets.
Highlights
Flow in a straight compound channel has both the main channel and the floodplain moving in the direction of the valley slope
For the case of meandering compound channels, in addition to the variation in velocity in the lower main channel and the upper floodplain region; flow in the outer floodplain region is determined to be faster than that of the floodplain within the meander belt [3]. [1, 4, 5] observed similar trends, for higher relative depths. [1] observed a uniform lateral velocity for lower relative depth of 0.15; for relative depth 0.5, the highest velocity occurred at the center of the floodplain. [6] presented that, at low over-bank flow, the interaction of flow above and below bank cause a significant deflection above the bank-full level while at deeper over-bank flows the interaction is less significant and the two layers are less dependent on each other
The data sets used here, are the large scale Flood Channel Facility (FCF) Phase B experimentations conducted by HR Wallingford, UK [8]; the small scale experimentations by the [15] at the Waterways Experiment Station in Vicksburg, Mississippi, USA and the experimental study of [16]
Summary
Flow in a straight compound channel has both the main channel and the floodplain moving in the direction of the valley slope. These velocity differences amongst the subareas of a compound meandering channel causes shear stress along the interface planes. Besides the horizontal interface between lower main channel and the upper floodplain, vertical interface differentiating the meander belt width and the outer floodplains is considered Taking into account these complicated flow interactions, different methods to predict stage-discharge has been presented [7,8,9,10,11], based on conventional channel division and classical Manning’s equation approaches. Procedure to calibrate the momentum transfer coefficient for a meandering compound channel from the measured discharge is proposed
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