Instability of stationary and uniformly moving cylindrical fluid bodies—II. Viscoelastic threads and experimental observations

The instability analysis of Part I is extended to the breakup of viscoelastic threads in fluid media (also possibly viscoelastic). Critical Growth rates and wave-numbers are calculated in terms of the viscosity ratio, the Ohnesorge numbers (continuous and dispersed phases), and elasticity numbers for each of the respective phases. Comparisons with results for Newtonian systems indicate viscoelastic threads to be less stable than Newtonian threads under similar conditions. Also, the critical wave-numbers observed with viscoelastic threads can differ significantly from those observed with Newtonian systems, particularly if the relative magnitudes of elasticity of the dispersed and continuous phases are quite different. Systems with similar magnitudes of elasticity in each phase exhibit wave-numbers similar to Newtonian systems of similar viscosities.Experimental results obtained from observations of fluid thread breakup in a Taylor four-roller device provide a basis for checking the predictions of the lineararized theory for both Newtonian and viscoelastic systems. In general, the agreement is good and the theoretical predictions of Parts I and II seem to be reasonable representations of experimental fact.