Stress Distribution in Creeping Flow around a Falling Sphere and Its Drag Force: —Measurement by flow birefringence technique—

Distributions of the primary normal stress difference and shear stress in creeping flow around a falling sphere were measured by the transmission light flow birefringence technique. Both distributions measured were found to be reasonable qualitatively and were considerably different in the neighborhood of the sphere from exactly analyzed values for a Newtonian fluid with the same value of viscosity, because of the elastic effect. The drag force acting on the sphere was calculated and used for quantitative evaluation of the measured values. The value calculated from the measured stress distributions was found to be close to the directly measured value, if suitable correction is made. It may be concluded that the transmission light flow birefringence technique can be employed for analyzing the stress distributions in axisymmetric flow fields with double refractive indices rising to the axis.