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Influence of skirt radius on performance of circular clarifier with density stratification
Author(s) -
Zhou Siping,
McCorquodale John A.
Publication year - 1992
Publication title -
international journal for numerical methods in fluids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 112
eISSN - 1097-0363
pISSN - 0271-2091
DOI - 10.1002/fld.1650140804
Subject(s) - clarifier , froude number , baffle , mechanics , turbulence , entrainment (biomusicology) , radius , inlet , stratification (seeds) , geotechnical engineering , geology , flow (mathematics) , environmental science , thermodynamics , physics , geomorphology , environmental engineering , rhythm , acoustics , computer security , computer science , seed dormancy , germination , botany , dormancy , biology
A numerical model for predicting the velocity field and suspended solids distribution in a secondary circular clarifier with density difference is evaluated. The density effects are characterized by the inlet densimetric Froude number. This study focuses on the role of the reaction baffle position in the performance of the clarifiers. For a large‐radius baffle and low densimetric Froude number an important phenomenon known as the density waterfall occurs in the inlet zone of the clarifiers. This was predicted by the numerical model and confirmed by the physical model tests. This model consists of a series of conservation equations for fluid mass and momentum and sediment concentration. The turbulent stresses are calculated by use of the eddy viscosity concept and the κ–ϵ. turbulence model. The study showed that the density waterfall results in high entrainment and high recirculation. A comparison of the solids concentration distribution for a tank with a small skirt radius to that with a large skirt radius shows that small skirt radius reduces the density waterfall effect and significantly improves the clarifier performance at low densimetric Froude numbers.