Photoelastic modulators have been used to study the anisotropies that the flow of viscous fluids, especially molten polymers, create. These specialized rheology techniques were developed in the laboratory of Dr. Gerald Fuller at Stanford University.
The heart of the experimental setup is a special flow cell that subjects a layer of the viscous fluid to time-dependent shear stresses. A laser beam, modulated by a photoelastic modulator, passes through the fluid at right angles to the shear stresses. The laser beam is then analyzed to determine birefringence and/or linear dichroism characteristics induced by the optical anisotropy of the sheared fluid.
S.J. Johnson, P.L. Frattini and G.G. Fuller, “Simultaneous Dichroism and Birefringence Measurements of Dilute Colloidal Suspensions in Transient Shear Flow”, J. Coll. Interfac. Sci. 104 (2) (1985) 440-45.
G.G. Fuller, S.J. Johnson and A.J. Salem, “Optical Rheometry of Dispersions”, Proceedings of the Tenth U.S. National Congress of Applied Mechanics, 1987.
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