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CFDModuleUsersGuide.pdf
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No Flux

The No Flux feature defines the condition that there is no flow across boundaries. Fluid does not move across impervious boundaries. This effect is represented with the No Flux boundary condition:

n u = 0

where n is the vector normal to the boundary.

Also, the No Flux boundary enforces zero gradient of fluid content across the selected boundary

n c1 = 0

This is the default boundary condition.

B O U N D A R Y S E L E C T I O N

From the Selection list, choose the boundaries to apply a no-flow condition.

Pressure and Saturation

The Pressure and Saturation feature makes it possible to specify the pressure and fluid volume fractions on a boundary. In many cases the distribution of pressure and saturation are known as numbers, distributions, or expressions involving time, t, for example.

B O U N D A R Y S E L E C T I O N

From the Selection list, choose the boundaries to specify the pressure and fluid saturation.

P A I R S E L E C T I O N

If Pressure and Saturation is selected from the Pairs menu, choose the pair to define. An identity pair has to be created first. Ctrl-click to deselect.

P R E S S U R E A N D S A T U R A T I O N

Enter a value or expression for the Pressure p (SI unit: Pa), and for the Saturation fluid 1 s1 (a dimensionless number between 0 and 1). The default values are 0. The saturation of Fluid 2 is then calculated as s2 = 1 s1.

T H E TW O - P H A S E D A R C Y ’ S L A W I N T E R F A C E | 337

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