Methods of determining flow velocity in open channels at turbulent regime

Summary

The turbulent flow structure and velocity distribution at turbulent liquid flow is considered. The methods of determining flow velocity in open channels based on keeping records of the speed of helix blade rotation, of the floating object speed, of the dynamic pressure, of the flow force impact; on the heat exchange principle; on measuring water amount entering the meter for the observation period; on the use of ultrasound; on the use of laser are presented. The error of measuring velocity by different methods is indicated. The profile of liquid velocity in a complete-mix activated sludge model system is specified.

Key words

turbulent flow , hydrodynamics , Reynolds number , actual velocity , Bernoulli equation , Pitot tube , ultrasonic flowmeter , laser method , complete-mix activated sludge system

Calculation of the longitudinal dispersion coefficient and number of cells in the model of series-connected reactors Part
1. Review and engineering analysis of methods

Summary

A review and comparative analysis of engineering methods for calculating the longitudinal dispersion coefficient and the equivalent number of cells in a model of series-connected reactors used to describe hydrodynamics in aeration tanks are presented. Both empirical and semi-empirical formulas (B. Chambers and G. L. Jones, K. L. Murphy and B. I. Boyko, P. Harremoes, K. Fujie, and others) and dimensional and substantiated models (B. M. Khudenko and E. A. Shpirt, O. Potier, and Y. Le Moullec) are considered. The classification of methods by the type of data used in calculations and by the degree of sensitivity to geometric and aerodynamic parameters is given. The criteria for the applicability of approaches at different stages of design, simulation and upgrade of the wastewater treatment facilities are formulated. The paper represents the first part of two articles and considers the calculation and interpretation of the number of cells in bioreactors. The second part will be on the practical application of methods by the example of aeration tanks of various configurations.

Key words

wastewater , bioreactor , hydrodynamics , longitudinal dispersion coefficient , series-connected reactor model , cell number