Boundary effects on jet flow patterns related to water quality and pollution problems

An experimental and analytical study of the modification of jet flow patterns by a nearby free surface and nearby horizontal or gently downward sloping plane bed is described. The patterns were found to be radically different from those for a deeply submerged jet. Both the free surface and bed tend to attract the jet and both cause spreading of the flow in their proximity. One boundary generally proves to be dominant, depending upon the geometrical parameters. The analytic study used Reichardt's hypothesis and its generalization for momentum, mass and heat flux by Alexander, Baron & Comings. The techniques are first applied to predict the effect of finite nozzle size on deeply submerged jet flows. Then the effect of the free surface on a shallow submerged jet is studied. A strong influence by a small initial upward deflection of the jet is indicated. A preliminary suggestion is made for a mathematical model to represent a shallow submerged jet in a shallow reservoir. The results may be applied in the study or design of discharge outlets, syphon spillways, hydraulic breakwaters and diffusion of tracers in streams. The diffusion of momentum, mass or heat may be studied using the analytic techniques.U.S. Department of the InteriorU.S. Geological SurveyOpe