Longitudinal Dispersion in Unsteady Pipe Flows
- 1 September 2021
- journal article
- research article
- Published by American Society of Civil Engineers (ASCE) in Journal of Hydraulic Engineering
- Vol. 147 (9), 04021033
- https://doi.org/10.1061/(asce)hy.1943-7900.0001918
Abstract
Temporal concentration profiles resulting from an injected pulse of fluorescent tracer were recorded at multiple locations along a pipe during controlled unsteady flow conditions. A linear temporal change in discharge over durations of 5, 10, or 60 s for both accelerating and decelerating flow conditions was studied. Tests were performed for flows that changed within the turbulent range, between Reynolds numbers of 6,500 and 47,000, and for laminar to turbulent flows, between Reynolds numbers of 2,700 and 47,000. Analysis of the data shows the limitations of employing steady-state routing of temporal concentration profiles in unsteady flow. Employing a flow weighted time routing approach, using tracer mean velocity and dispersion coefficients, provides accurate predictions of mixing in unsteady flow. For decelerating flows, longitudinal dispersion coefficients were lower than for the equivalent mean steady discharge. Previously unreported disaggregation of the tracer cloud was observed during all experiments accelerating from laminar to turbulent conditions.Keywords
This publication has 20 references indexed in Scilit:
- Residence Time Distributions for Turbulent, Critical, and Laminar Pipe FlowJournal of Hydraulic Engineering, 2016
- Longitudinal Dispersion Coefficients Within Turbulent and Transitional Pipe FlowPublished by Springer Science and Business Media LLC ,2013
- Eulerian–Lagrangian Method for Constituent Transport in Water Distribution NetworksJournal of Hydraulic Engineering, 2007
- Effects of wetland depth and flow rate on residence time distribution characteristicsEcological Engineering, 2004
- Rapid temporal acceleration of a turbulent pipe flowJournal of Fluid Mechanics, 2004
- A study of turbulence under conditions of transient flow in a pipeJournal of Fluid Mechanics, 2000
- Residence time distribution for unsteady-state systemsChemical Engineering Science, 1995
- Mixing in RiversPublished by Elsevier BV ,1979
- The approach to normality of the concentration distribution of a solute in a solvent flowing along a straight pipeJournal of Fluid Mechanics, 1970
- Continuous flow systems: Distribution of residence timesChemical Engineering Science, 1953