Numerical Investigation of Baffle Effect on the Flow in a Rectangular Primary Sedimentation Tank
It is essential to have a uniform and calm flow field
for a settling tank to have high performance. In general, the
recirculation zones always occurred in sedimentation tanks. The
presence of these regions may have different effects. The nonuniformity
of the velocity field, the short-circuiting at the surface and
the motion of the jet at the bed of the tank that occurs because of the
recirculation in the sedimentation layer, are affected by the geometry
of the tank. There are some ways to decrease the size of these dead
zones, which would increase the performance. One of the ways is to
use a suitable baffle configuration. In this study, the presence of
baffle with different position has been investigated by a finite volume
method, with VOF (Volume of Fluid) model. Besides, the k-ε
turbulence model is used in the numerical calculations. The results
indicate that the best position of the baffle is obtained when the
volume of the recirculation region is minimized or is divided to
smaller part and the flow field trend to be uniform in the settling
zone.
[1] Silveston, P.L., J.F. Cordoba-Molina, and R.R. Hudgins, "The use of
flow contraction to improve clarifier performance". Water Science and
Technology, 13 1981: p. 385-394.
[2] Hamlan, M.J. and A.H.A. Wahab, "Settling Characteristics of Sewage in
Density Currents". Water Research, 4 1970: p. 251-271.
[3] Crosby, R.M., Evaluation of the Hydraulic characteristics of activated
sludge secondary clarifiers. 1984, Environmental Protection
Agency,Office of Research and Development: Washington, D.C. U.S. p.
84-131.
[4] Bretscher, U., P. Krebs, and W.H. Hager, "Improvement of flow in final
settling tanks". J. Enviromental Engineering, ASCE, 118 1992.(3): p.
307-321.
[5] Zhou, S., J. McCorquodale, and Z. Vitasovic, "Influences of density on
circular clarifiers with baffles". Journal of Environmental Engineering,
ASCE, 118 1992.(6): p. 829-847.
[6] Huggins, D.L., R.H. Piedrahita, and T. Rumsey, "Analysis of sediment
transport modeling using computational fluid dynamics (CFD) for
aquaculture raceways". Aquacult. Eng., 31 2005: p. 277-293.
[7] Fan, L., et al., "Numerical simulation of secondary sedimentation tank
for urban wastewater". J. Chin. Inst. Chem. Eng., 38 2007: p. 425-433.
[8] Tamayol, A., B. Firoozabadi, and G. Ahmadi, "Effects of Inlet Position
and Baffle Configuration on Hydraulic Performance of Primary Settling
Tanks". Journal of Hydraulic Engineering, ASCE., 134 2008.(7): p.
1004-1009.
[9] Goula, A.M., et al., " A CFD methodology for the design of
sedimentation tanks in potable water treatment case study: the influence
of a feed flow control baffle". Chem. Eng. J., 140 2007: p. 110-121.
[10] Sammarraee, M.A. and A. Chan, "Large-eddy simulations of particle
sedimentation in a longitudinal sedimentation basin of a water treatment
plant. Part 2: The effects of baffles". Chemical Engineering Journal 152
2009: p. 315-321.
[11] Hirt, C.W. and B.D. Nichols, "Volume of Fluid (VOF) Method for the
Dynamics of Free Boundaries". J. Comp. Phys., 39 1981: p. 201-225.
[12] Hirt, C.W. and J.M. Sicilian, A Porosity Technique for the Definition of
Obstacles in Rectangular Cell Meshes, in Fourth International Conf.
Ship Hydro. 1985, National Academy of Science: Washington, DC. p. 1-
19.
[13] Harlow, F.H. and P.I. Nakayama, "Turbulence Transport Equations".
Phys. of Fluids, 10 1967.(11): p. 2323-2333.
[14] Svendsen, I. and J. Kirby, Numerical study of a turbulent hydraulic
jump, in 17th ASCE Engineering Mechanics Conference. 2004:
University of Delaware, Newmark, DE.
[15] FlowScience, Flow-3D user manual. 2009.
[16] Imam, E., J.A. McCorquodale, and J.K. Bewtra, "Numerical Modeling of
Sedimentation Tanks". Journal of Hydraulic Engineering, ASCE., 109
1983.(12): p. 1740-1754.
[17] Hirt, C.W., Identification and Treatment of Stiff Bubble Problems. 1992,
Flow Science Inc.
[1] Silveston, P.L., J.F. Cordoba-Molina, and R.R. Hudgins, "The use of
flow contraction to improve clarifier performance". Water Science and
Technology, 13 1981: p. 385-394.
[2] Hamlan, M.J. and A.H.A. Wahab, "Settling Characteristics of Sewage in
Density Currents". Water Research, 4 1970: p. 251-271.
[3] Crosby, R.M., Evaluation of the Hydraulic characteristics of activated
sludge secondary clarifiers. 1984, Environmental Protection
Agency,Office of Research and Development: Washington, D.C. U.S. p.
84-131.
[4] Bretscher, U., P. Krebs, and W.H. Hager, "Improvement of flow in final
settling tanks". J. Enviromental Engineering, ASCE, 118 1992.(3): p.
307-321.
[5] Zhou, S., J. McCorquodale, and Z. Vitasovic, "Influences of density on
circular clarifiers with baffles". Journal of Environmental Engineering,
ASCE, 118 1992.(6): p. 829-847.
[6] Huggins, D.L., R.H. Piedrahita, and T. Rumsey, "Analysis of sediment
transport modeling using computational fluid dynamics (CFD) for
aquaculture raceways". Aquacult. Eng., 31 2005: p. 277-293.
[7] Fan, L., et al., "Numerical simulation of secondary sedimentation tank
for urban wastewater". J. Chin. Inst. Chem. Eng., 38 2007: p. 425-433.
[8] Tamayol, A., B. Firoozabadi, and G. Ahmadi, "Effects of Inlet Position
and Baffle Configuration on Hydraulic Performance of Primary Settling
Tanks". Journal of Hydraulic Engineering, ASCE., 134 2008.(7): p.
1004-1009.
[9] Goula, A.M., et al., " A CFD methodology for the design of
sedimentation tanks in potable water treatment case study: the influence
of a feed flow control baffle". Chem. Eng. J., 140 2007: p. 110-121.
[10] Sammarraee, M.A. and A. Chan, "Large-eddy simulations of particle
sedimentation in a longitudinal sedimentation basin of a water treatment
plant. Part 2: The effects of baffles". Chemical Engineering Journal 152
2009: p. 315-321.
[11] Hirt, C.W. and B.D. Nichols, "Volume of Fluid (VOF) Method for the
Dynamics of Free Boundaries". J. Comp. Phys., 39 1981: p. 201-225.
[12] Hirt, C.W. and J.M. Sicilian, A Porosity Technique for the Definition of
Obstacles in Rectangular Cell Meshes, in Fourth International Conf.
Ship Hydro. 1985, National Academy of Science: Washington, DC. p. 1-
19.
[13] Harlow, F.H. and P.I. Nakayama, "Turbulence Transport Equations".
Phys. of Fluids, 10 1967.(11): p. 2323-2333.
[14] Svendsen, I. and J. Kirby, Numerical study of a turbulent hydraulic
jump, in 17th ASCE Engineering Mechanics Conference. 2004:
University of Delaware, Newmark, DE.
[15] FlowScience, Flow-3D user manual. 2009.
[16] Imam, E., J.A. McCorquodale, and J.K. Bewtra, "Numerical Modeling of
Sedimentation Tanks". Journal of Hydraulic Engineering, ASCE., 109
1983.(12): p. 1740-1754.
[17] Hirt, C.W., Identification and Treatment of Stiff Bubble Problems. 1992,
Flow Science Inc.
@article{"International Journal of Earth, Energy and Environmental Sciences:57035", author = "M. Shahrokhi and F. Rostami and M.A. Md Said and S. Syafalni", title = "Numerical Investigation of Baffle Effect on the Flow in a Rectangular Primary Sedimentation Tank", abstract = "It is essential to have a uniform and calm flow field
for a settling tank to have high performance. In general, the
recirculation zones always occurred in sedimentation tanks. The
presence of these regions may have different effects. The nonuniformity
of the velocity field, the short-circuiting at the surface and
the motion of the jet at the bed of the tank that occurs because of the
recirculation in the sedimentation layer, are affected by the geometry
of the tank. There are some ways to decrease the size of these dead
zones, which would increase the performance. One of the ways is to
use a suitable baffle configuration. In this study, the presence of
baffle with different position has been investigated by a finite volume
method, with VOF (Volume of Fluid) model. Besides, the k-ε
turbulence model is used in the numerical calculations. The results
indicate that the best position of the baffle is obtained when the
volume of the recirculation region is minimized or is divided to
smaller part and the flow field trend to be uniform in the settling
zone.", keywords = "Sedimentation tanks, Baffle, Numerical Modeling,
VOF, Circulation Zone", volume = "5", number = "10", pages = "588-6", }