Abstract

The industrial effluents and municipal wastewater plant effluents discharged into a stream are expected to undergo dilution in a short reach of the stream. To permit this, the devices used to discharge the effluent should ensure rapid mixing of the effluent in the stream. Jets act as simple and efficient devices that accomplish this task. Counter flowing wall jets located in closed conduits can also be used for efficient mixing of chemicals used in water and wastewater plants. The increased interest in the use of cross jets and counter flowing jets to ensure proper mixing of effluents in a stream can be traced to the larger scales of mixing achieved by these devices, as compared to the traditional co-flowing jet devices. Existing counter flowing wall jet studies are mostly limited to the determination of the mean flow characteristics of the jet. These include the determination of the functional relationship among the main jet parameters such as the jet velocity ratio, the width of the recirculation zone and the penetration length of the jet. In the present study, the mean and turbulent mixing characteristics of the counter flowing wall jets were determined experimentally using a Laser Doppler velocity meter (LDA). This information was used to find the dependence of the length scales and the velocity scales of the counter flowing wall jet on the basic parameters. To validate the experimental procedure, the mean velocity profiles, turbulent components and jet expansion angle of wall jets were determined. The validation was quite good. (Abstract shortened by UMI.)