Viscoelastic effects in patterns between miscible liquids

Water injected into aqueous solutions of polyethylene oxide in a Hele-Shaw cell shows a wide variety of patterns as four control parameters are independently varied. Despite the strong variation of patterns, both the initial unstable length scale and the mean and standard deviation of Fourier modes of averaged late-time patterns show a smooth variation with a dimensionless number constructed from the ratio of the imposed shear time scale to the polymer-relaxation time