Fluid mechanics of fibre suspensions related to papermaking - DiVA
Fluid mechanics of fibre suspensions related to papermaking - DiVA
Fluid mechanics of fibre suspensions related to papermaking - DiVA
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2.1. TWO-PHASE FLOW 13<br />
or as a mass coupling measure–the number <strong>of</strong> particles in a unit volume and<br />
the probability <strong>of</strong> collisions.<br />
The forces acting on the particle are subdivided in<strong>to</strong>: (a) body forces, such<br />
as gravity or electrostatic forces, and (b) surface forces, due <strong>to</strong> drag and lift<br />
forces, and result in a momentum coupling between the two phases. In general,<br />
the surface forces depend on particle shape and orientation, though also on the<br />
flow parameters such as the viscosity, Reynolds number, turbulence intensity<br />
etc. One fundamental example is S<strong>to</strong>kes flow around a non-rotating sphere<br />
falling in a liquid under the influence <strong>of</strong> gravity at low Reynolds number, for<br />
which the drag force varies linearly and inversely with Reynolds number.
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