Kinematic structure of flow in a trapezoidal channel

Abstract

1. Under conditions of designing earth canals for a maximum permissible noneroding velocity a trapezoidal channel shape is potentially unstable. 2. In trapezoidal channels the distribution of the velocity over the width does not correspond to the calculation by the Chezy formula with the use of local (on verticals) hydraulic radii. 3. To provide slope stability of trapezoidal canals it is necessary when estimating the design velocity to take into account the actual distribution of the velocity over the channel width, which practically leads to a decrease of the design velocity. 4. From the viewpoint of cost effectiveness of designing large canals in a deformable earth channel it is necessary to reject trapezoidal shapes. It is necessary to adopt a parabolic configuration corresponding in shape to the diagram of the velocity distribution over the channel width; in this case the design flow velocity can be taken with respect to a depth close to the maximum.