Turbulence modelingTurbulence modeling Simulation setups...

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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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