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Turbulence modeling Turbulence modeling
Cavitation modeling (VOF)
Mass Transfer Modeling
Simulation setups
C i l d i d id i d d Computational domain and grid independency
Results Results
Conclusion
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Turbulence modeling
Multiphase Modeling (VOF)(VOF)
Mass Transfer Modeling
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Incompressible OEEVM LES
LES i t t ith RANS h LES in contrast with RANS approaches
The large energy-containing structures(resolve)and the smaller, more isotropic sub-gridand the smaller, more isotropic sub gridstructures(are modeled)
Applying low-pass filtering, using a pre-definedfilter kernel function G = G(x,Δ)( , )
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Filtered Navier-Stokes and continuity equation are usuallyprovided by convolving all dependent variables whit G =G( Δ)G(x,Δ)
Eliminate eddies smaller than the filter width (Δ)( )
B is the SGS stress tensor Onl B needs to be modeled Only B needs to be modeled
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eddy or sub grid viscosity modelseddy or sub grid viscosity models
One-Equation Eddy-Viscosity Model (OEEVM) :q y y ( )
K (SGS kinetic energy)
AND
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volume fraction, α one fluid two-phase mixture one fluid, two-phase mixture
Transport equation:p q
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Sauer model
necessary to supply some parameters to the model
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Kunz model vaporization occurs when the pressure is below vaporization occurs when the pressure is below
the vapor pressure
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Only at the free surfaces
Fs, is the surface tension
openFoam structure l openFoam structure Big library Applications
Solvers
U ili i MultiPhaseSolvers
interPhaseChangeFoam
Utilities
interPhaseChangeFoam
Cl k Y h d f il i h 8 d AOA ( 0 8 R 7 105 ) Clark-Y hydrofoil with a 8 degree AOA ( = 0.8 و Re=7×105 )
= 0 8 و Re=7×105 0.8 و Re 7×10
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Structured Mesh(gambit) Structured Mesh(gambit)
y+ is about 2 y is about 2
There is 290 cell on the upper wall and there is about There is 290 cell on the upper wall and there is about 120000 cell in the total domain
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There are 4 Grids:
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structured quadrilateral meshes structured quadrilateral meshes 130 cells on the upper wall of the hydrofoil and 87 cells on the lower wall 2.8×106 cells in the total domain y+ around 2
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The cavitation shape with experimental(right) and numerical results(left)
t/T=0.11
t/T=0.43
t/T=0.8
t/T=1
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Start Point Of CavitationKunz model 10 mmSauer model 13.9 mmexperiment 14 mm
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Velocity profile (dashed line is from experiments)
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Variation of Cl in a period of time for σ=0.8 Average amounts of C و C Average amounts of CL و CD
methodmethod
2D - simmulation 0.149 0.835
E i t 0 12 0 76Experiment 0.12 0.76
Error (%) 24 9
method
3D simmulation 0 15 0 83D - simmulation 0.15 0.8
Experiment 0.12 0.76
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Error (%) 25 5
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Cavitatig flow simulation using LES/VOF and Kunz mass transfer modeltransfer model
Agreements between experimental and numerical results Agreements between experimental and numerical results
hydrodynamic coefficientsy ycavitation shapecavitation dynamic LES in contrast with RANS
2D and 3D similarities
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Thank youThank you
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