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Lift Force
Lift Force on a Particle Touching a Plane
Leighton and Acrivos (1985) obtain the expression for the lift on
the spherical particles resting on a plane substrate
as shown in Figure 3. They found
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(10)
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| Calculation Model |
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Lift Force
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which is always pointing away from the wall. Note that the Saffman expression given by Equation 1 may be restated as
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(11)
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Equation 6 with IL given by Equation 7 reduces to Equation 10 for K=1,^G=-1.
For small particles in turbulent flows, using
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(12)
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where u* is the shear velocity, equations 10 and 11 become
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(13)
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(14)
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where
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(15)
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Experimental studies of lift force were preformed for generally larger particles in the range of 100 to several hundred
µm. Hall (1998) found
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(16)
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Mollinger and Nieuwstadt (1996) found
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(17)
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Figure 4 compares the model predictions with the experimental data of Hall. It is seen that the experimental data is
generally much higher than the theoretical models.
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