Fluid Mechanics Research Group

Two phase modelling for industrial applications

Prof A.E.Holdø & R.K.Calay

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A case study

• Multiphase flows • Investigation into gravity based oil-

water separator • Using IPSA model• Parametric studies• A design tool

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A typical separator

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Flow mechanisms

• Liquid/liquid flow• Density difference

Gravitational force• Viscosity difference

Viscous shear

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CFD Model

Solid blockages

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Boundary conditions

• Inlet: water:oil 50:50• Velocity for the mixture =-.25m/s• Symmetry boundary conditions

along y-z plane at x=0• Outlets: free• All other walls as no-slip walls

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Mesh models

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Comparison of velocity profiles for different mesh models• Variation of velocity at outlet2

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.0 0.3 0.6 0.9 1.2 1.5

Height, m

Velo

cit

y, m

/s

28160

42240

63360

95040

172800

360000

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Variation of oil volume fraction at outlet2

Variation of oil fraction at outlet-2 w.r.t. y-axis

0.92

0.94

0.96

0.98

1.00

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Height, m

Vo

lum

e fr

acti

on

28160

42240

63360

95040

172800

360000

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Results:Distribution phase volume fraction at x=0, y-z plane

Inlet velocity = -0.25m/s

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Velocity contours at y-z mid plane

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Velocity-vectors at mid y-z plane

Inlet velocity =-0.25m/s, particle =1mm

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Velocity at various locations along the z-axis

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Streamlines

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Parametric comparisons

variation of velocity along z-axis at y=0.628m, x=0

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0 3 6 9 12Z, m

Ve

l.m/s

1mm

2mm

3mm

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Water volume fraction for particle size; .25mm and 1mm

Inlet velocity = -0.25m/s

Inlet velocity = -0.25m/s, particle =1mm

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Different inlet velocity:

0.25m/s ; 0.5m/s

Inlet Velocity = -0.5m/s, particle =1mm

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Oil volume fraction 0.25m/s; 0.5m/s

Inlet Velocity =-0.5m/s

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Changing the weir height

0.5m; 0.805m

IPSA4_7,h=0.5m, v=0.5m/s

Inlet Velocity =-0.5m/s

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Conclusions

• Convergence is difficult compared to single phase

• Mesh, relaxation factor, initialisation affect the solution

• Good results for preliminary investigations

• Data needed for validation

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Further Modifications

• Transient simulation • Models for emulsification,

coagulation and bubble formation• Effect of solid particles