Stokes’s equation

Equations 9.6 and 9.8 were derived by Stokes and are known as Stokes s equations for steady creeping flow round a sphere. 

To highlight the difference from the classical Stoke s equation, the density difference in the latter is (ps—pt), where ps is the skeletal density of the rigid particle. Now, it is easy to illustrate the analogy to a porous particle. A porous particle can be viewed as an aggregate,... 

The radius R is related to the friction constant F in sedimentation by Stokes s equation ... 

Only the billowing have t>een lonnd to enhance the settling ol emulsions lime. heat, lorced coalescence, chemical aids and centrifuges I hese are the things which modify the parameters in Stoke s equation. 

Forced coalescence. Referring again to Stoke s equation. notice that the panicle radius occurs taken to (lie second power. II the particle can Ik- increased, the settling velocity increases by the square ol this change. Particle size then becomes the overriding parametei in the separation process. 

Equation (26) is called the Stoke s equation and is applicable to the fall of spherical bodies in all types of liquid media, provided the radius of the falling body r is large compared to the size of the solvent molecule. If the difference Is not large, the body tends to drop instead of falling with a constant velocity. 

Stokes s equation is limited to particle Reynolds numbers smaller than 0.1, but has often been used for particle Reynolds Numbers as large as 1 (based on sphere diameter dj. 

Richards (1908) demonstrated that Stokes s equation is inaccurate for particles with a diameter larger than 0.2 mm (0.00787 in, mesh 70) and conducted extensive tests for... 

Figure C.ll NaCl at 298 K. Curve (a), Onsager s equation curve (b), Robinson and Stokes s equation (a = 4 x 10" ° m)...

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