Application of some hydraulic principles to flow measurement

For flow near the end section of a trapezoidal channel, the velocity distribution is non-uniform and the streamlines are curved. At the end section of the overfall, the streamline pattern in the vertical plane of channel symmetry can be determined using the measured axial velocity data and the water surface profiles. The streamline pattern permits the evaluation of the streamline curvature, which in turn yields the curvature correction required to obtain the true static pressure profile at the end section. In the region above the maximum velocity point near the end depth, energy relationships determined on the basis of the measured velocity and pressure field data confirm the fact that the total energy is essentially constant. The pressure head coefficient at the end section is a dominant parameter that influences the relationship between the channel discharge and the end depth. Single slit weirs have been recently investigated to show that small discharge rates can be measured accurately by them. This concept has been applied to the flow through multislit weirs. This can extend the capacity of the slit weirs to measure accurately both low and high discharge rates. For this purpose the hydraulic concept of images is used to form a bank of slit weirs whose flow characteristics are essentially similar to the single weir. The multislit weir can accurately measure both very low and very large discharg