Jet dispersion in channels
This is an experimental and theoretical investigation of the dispersion of a round water jet discharging at various angles into a rectangular channel. A fundamental study of the jet is not only essential for a better understanding of the flow conditions produced by confined water jets but for a scientific approach to the design of hydraulic structures and to determine an efficient form of stilling basin for high velocity discharge from pipe outlets. The Laser Doppler Anemometry (LDA) technique was adapted for measurement of mean velocities and turbulence characteristics,, without any interference in the flow, and was utilised for the investigation of the complex three dimensional circulating flow which was experienced in the channel. In the experiments the inclination of the jet was varied from 45 to 90 degrees to the bed of the channel, while differing ratios of channel width and depth to jet diameter were studied for various Froude numbers. Detailed measurements of velocity decay, normal and lateral velocity profiles, distributions of pressure and turbulence characteristics have been carried out for selected flow conditions relating to the 45 degree oblique and vertical jet in order to determine the flow pattern and head dissipations. The experimental results have been analysed and compared with Glauert Is theory for a radial wall jet as a first approximation neglecting gravity forces when small compared with turbulent forces. Based on these results erosion experiments and model studies using a solid apron and a sand bed downstream, have been conducted to predict the minimum size of an efficient stilling basin and dimensions of any required blocks. Finally generalised design guide-lines and a standard code of practice have been developed for a stilling basin with high velocity pipe outlets. The research work will provide practical information and design procedures for consultants and other organisations working on the design and maintenance of a variety of water projects both in the UK and overseas.