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Numerical Modeling of Inclined Negatively Buoyant Jets
Presentation by: Hossein Kheirkhah
Graduate Student in Civil Engineering
Dep. of Civil Engineering University of Ottawa
CANADA
ICDEMOS April2014
Outline
• Introduction • Objectives • Definitions • Numerical Details • Results • Conclusions • Future Work • References
Numerical Modeling of Inclined Negatively Buoyant Jets
Hollywood sewage outfall
Introduction
Effluent (USEPA Definition): Wastewater, treated or untreated, that flows out of a
treatment plant, sewer, or industrial outfall. Generally refers to wastes discharged into surface waters.
Effluent Sources • Desalination Plants (arid and semi-arid countries) • Nuclear Power Plants • Municipal Effluents
From: http://www.cbc.ca Al Ghubrah desalination plant (biggest in Oman). (photo by
Hamdi Al-Barwani)
St. Lawrence River. From: EC
Numerical Modeling of Inclined Negatively Buoyant Jets
Introduction (Cont’d)
Effluent Discharges into the water body: 1. Surface Discharges 2. Submerged Discharges
From: www.sciencephoto.com
From: www.sciencephoto.com
Numerical Modeling of Inclined Negatively Buoyant Jets
Introduction (Cont’d)
Submerged Discharges a. Negatively Buoyant Jets b. Positively Buoyant Jets
Numerical Modeling of Inclined Negatively Buoyant Jets
Objectives
• Evaluating the performance of numerical model
• Finding the appropriate numerical model/solver
• Implementations in the base-code
• Evaluation of various turbulence models
• Finding the stable numerical schemes
Numerical Modeling of Inclined Negatively Buoyant Jets
Definitions
• Dilution a
a
CCCCS
−−
= 0 C0: Concentration at Source Ca: Ambient Concentration C: Concentration at Mesh Grid
Numerical Modeling of Inclined Negatively Buoyant Jets
Definitions (Cont’d)
Outer-half
inner-half
Numerical Modeling of Inclined Negatively Buoyant Jets
Numerical Details Governing Equations
Cont.
Mom.
Temp.
0=∂
∂
j
j
xu
)(kk
effj
j
xT
xk
xTu
tT
∂∂
∂∂
=∂
∂+
∂∂
Heat transfer coefficient Effective kinematic viscosity teff υυυ += 0
0
0
PrPrυυ
+=t
teffk
Con. )(kkj
j
xC
xD
xCu
tC
∂∂
∂∂
=∂
∂+
∂∂
ρρυ
ρ∆
−∂∂
∂∂
+∂∂
−=∂∂
+∂∂
ij
ieff
jiij
j
i gxu
xxPuu
xtu )(1)(
Millero and Poisson (1981)
Numerical Modeling of Inclined Negatively Buoyant Jets
Numerical Details (Cont’d) OF toolbox
The OpenFOAM (OPEN Field Operation And Manipulation) CFD Toolbox is a free, open source CFD software package produced by OpenCFD Ltd (2011). Advantages: • Open Source
• Finite Volume Method
• Working on LINUX OS
• Variety of Utilities and Applications
Numerical Modeling of Inclined Negatively Buoyant Jets
Numerical Details (Cont’d) Solver
Solver: mypisoFoam A transient solver for incompressible flow Transport Eqns. for U, S and T are solved implicitly P is solved explicitly in PISO algorithm Density varies with S and T (Millero and Poisson, 1981)
Numerical Modeling of Inclined Negatively Buoyant Jets
Numerical Details (Cont’d)
Simulation process priority in OF
Numerical Modeling of Inclined Negatively Buoyant Jets
Seven RANS Turbulence Models:
Numerical Details (Cont’d) Turbulence Modeling
Four LEVMs
Standard k-ε
RNG k-ε realizable k-ε SST k-ω
Two RSMs Launder-Gibson
LRR
One NLEVM: nonlinear k-ε Buoyant wall jet study
Inclined dense jet study
Numerical Modeling of Inclined Negatively Buoyant Jets
Results
45° inclined dense jet, LRR turbulence model
Numerical Modeling of Inclined Negatively Buoyant Jets
Numerical test cases
Case Inclined Angle
ϴ
Initial Inlet
Height y0
(mm)
D (mm)
U0 (m/s)
Δρ/ρ0 (%)
Fd Lm (mm)
y0/Lm
1 30.00 11.17 6.50 1.00 1.98 28.10 172.00 998.20
2 45.00 12.92 6.00 1.17 1.98 34.30 193.00 999.97
Results (Cont’d)
Numerical Modeling of Inclined Negatively Buoyant Jets
Results (Cont’d)
Normalized terminal rise height as a function of initial discharge angle
Numerical Modeling of Inclined Negatively Buoyant Jets
Results (Cont’d)
Minimum dilution at the return point as a function of initial discharge angle
Numerical Modeling of Inclined Negatively Buoyant Jets
Results (Cont’d)
Comparison of numerical and experimental coefficients for 45° inclined jets
Avg=1.62
Avg=3.08
Avg=1.48
Avg=1.48
Avg=1.80
Avg=0.44
Numerical Modeling of Inclined Negatively Buoyant Jets
Results (Cont’d) Inclined dense jet
Normalized concentration profiles at various downstream cross-sections for a 30° jet
Numerical Modeling of Inclined Negatively Buoyant Jets
Results (Cont’d) Inclined dense jet
Comparison of concentration spread width along the trajectory. Lower bc Comparison of concentration spread width along the trajectory. Upper bc
Numerical Modeling of Inclined Negatively Buoyant Jets
• Numerical results of selected turbulence models show good agreement for the velocity and concentration fields between both experimental and numerical studies.
• Realizable k-ε and LRR turbulence models performed best amongst the
seven models investigated.
• Geometrical characteristics of inclined dense jets have been predicted fairly well.
• Cross-sectional U & C profiles follow the Gaussian pattern better in outer-half of the jet as well as closer area to source than the inner-half.
Conclusions
Numerical Modeling of Inclined Negatively Buoyant Jets
• Improved mesh grid system: unstructured, non-conformal, etc.
• Improved turbulence models
• More advanced numerical schemes
• Ambient water characteristics: cross-flow, stratification, wave, etc.
Future Work
Numerical Modeling of Inclined Negatively Buoyant Jets
References Bleninger, T., and Jirka, G. H. (2008). “Modeling and environmentally sound
management of brine discharges from desalination plants.” Desalination, 221:585–597.
Huai, W., Li, Z. Qian, Z., Zeng, Y., & Han, J. (2010). ”Numerical Simulation of
Horizontal Buoyant Wall Jet.” J. of Hydrodynamics, 22(1):58-65. Kheirkhah Gildeh, H., Mohammadian, M., Nistor, I., and Qiblawey, H. (2012).
“Numerical modeling of turbulent buoyant wall jets in stationary ambient water.”, Submitted to J. Hydraul. Eng., ASCE.
Kheirkhah Gildeh, H., Mohammadian, M., Nistor, I., and Qiblawey, H. (2013).
“Numerical modeling of 30° and 45° inclined dense turbulent jets in stationary ambient.”, Submitted to J. Environ. Fluid Mech., Springer.
Law, A. W., and Herlina. (2002). “An experimental study on turbulent circular wall
jets.” J. Hydraul. Eng., 128(2):161-174. OpenCFD Limited. (2011). OpenFOAM - Programmer’s Guide, Version 2.1.1. Shao, D., nad Law, A. W. (2010). “Mixing and boundary interaction of 30 and 45
inclined dense jets.” J. Environ. Fluid Mech., Springer 10:521-553. Sharp, J. J. (1975). “The use of a buoyant wall jet to improve the dilution of a
submerged outfall.” Proc. Instn. Civ. Engrs, Part 2, 59:527-534, London, UK.
Numerical Modeling of Inclined Negatively Buoyant Jets
Thank you!
Numerical Modeling of Inclined Negatively Buoyant Jets
Thank you!
Numerical Modeling of Turbulent Wall Jets in Stationary Ambient Water
Definitions General
• Densimetric Froude #
• Momentum Length Scale
• Source Length Scale
Dimensional Analysis
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Numerical Details
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Numerical Modeling Procedure
Mathematical Model (PDEs, BC)
Descritization Method (FDM, FVM, FEM)
Finite Approximation (Numerical Schemes)
Solution Method
Convergence Criteria (Stopping Condition)
Numerical Details (Cont’d) FVM
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Numerical Details (Cont’d) Other Properties
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Numerical Schemes: 1st and 2nd order schemes div(phi,S) Gauss upwind;
Gaussian Integration Interpolation Scheme
Numerical Solution Preconditioned bi-conjugate gradient
Diagonal incomplete-LU
Numerical Details (Cont’d) Turbulence Modeling
NS RANS Take Average
jiuuρ
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Algebraic Models: An algebraic Eqn. for turbulent viscosity
?
1 Eqn. Models: A transport Eqn. is solved (for turbulent kinetic energy)
2 Eqn. Models: Two transport Eqn. is solved (e.g. for k & ε)
Reynolds Stress Velocity Boussinesq assumption
RSM: A transport Eqn. for Reynolds stress tensor
Centerline trajectory. Fr # about 12
Results (Cont’d) Buoyant wall jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Centerline trajectory. Fr # about 20
Comparison of the maximum velocity decay
Results (Cont’d) Buoyant wall jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Spanwise w-velocity profiles at y=ym for case # 3
Results (Cont’d) Buoyant wall jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Streamwise temperature profiles for case # 3
Results (Cont’d) Buoyant wall jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Spanwise temperature profiles for case # 3
Results (Cont’d) Buoyant wall jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Comparison of the maximum temperature decay
Results (Cont’d) Buoyant wall jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Results (Cont’d) Inclined dense jet
Normalized centerline trajectory for 30° inclined dense jet Normalized centerline trajectory for 45° inclined dense jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Results (Cont’d) Inclined dense jet
Normalized vertical location of centerline peak as a function of initial discharge angle
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Results (Cont’d) Inclined dense jet
Normalized horizontal location of return point as a function of initial discharge angle
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Results (Cont’d) Inclined dense jet
Normalized variation of dilution along the inlet height level for a 30° jet Normalized variation of dilution along the inlet height level for a 45° jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Results (Cont’d) Inclined dense jet
Comparison of normalized centerline max velocity decay for a 30° jet Comparison of normalized centerline max velocity decay for a 45° jet
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Results (Cont’d) Inclined dense jet
Cross-sectional C distribution at various downstream locations
Numerical Modeling of Thermal/Saline Discharges in Coastal Waters
Results (Cont’d) Inclined dense jet
Normalized velocity profiles at various downstream cross-sections for a 30° jet