Anisotropic Stokes drag and dynamic lift on spheres sedimenting in a nematic liquid crystal
Joel B Rovner1, Daniel H Reich, Robert L Leheny
1Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, United States.
Abstract:
The motion of silica spheres with homeotropic anchoring sedimenting within nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) has been studied at low Ericksen number. The magnitude of the spheres' velocity depends on the angle θ between the far-field nematic director and the gravitational force, indicating an anisotropic Stokes drag. When the director is oriented at an oblique angle to the gravitational force, the velocity also acquires a component normal to the force, demonstrating the existence of a lift force generated by the fluid. The magnitude and direction of the velocity as functions of θ quantitatively obey theoretically predicted forms.
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