The study aims at quantifying the effect of fluid elasticity on frictional pressure drop for the flow of viscoelastic fluid through a helical coil. Aqueous solutions of polyacrylamide (PAA) in the concentration range 0.25 %–0.5 % (wt/vol.) were used as test fluids. The fluids were characterized using dynamic rheometer under rotational and oscillatory modes. The rheological study depicts that th...

– The onset of surface waves in a vibrated layer of a viscoelastic fluid is investigated theoretically. For vibration frequencies close to the inverse relaxation time of the non-Newtonian fluid, surface waves respond harmonically instead of being subharmonic as is usually the case in Newtonian fluids. This prediction has been made on the basis of the Maxwell model for viscoelastic fluids, but t...