The time evolution of the distance between two identical
spheres falling in a viscoelastic fluid has been analyzed exper-
imentally. The working fluid was a dilute solution of polyacry-
lamide in an aqueous solution of glycerin. Several concentra-
tions of polyacrylamide and glycerin have been used in order to
analyze fluids with different viscoelastic properties. Two experi-
mental configuration allow analyzing the effect of the boundary
conditions. A CCD camera was used to record the movement of
the spheres allowing the computation of evolution of the space
separation between them. It has been found that beyond cer-
tain critical initial elapsed time (tdc) the distance between the
spheres grows in time, while the distance decrease for elapsed
times smaller than the tdc. Reduction of the shear-thinning ef-
fect tends to eliminate the repulsion interaction.
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.