Effect of lattice defects on Hele-Shaw how over an etched lattice

We examine the patterns formed by injecting nitrogen, gas into the center p f a horizontal, radial Hele-Shaw cell filled with paraffin oil. We use smoo th plates and etched plates with lattices having different amounts of defec ts (0-10 %). hi all cases, a quantitative measure of the pattern ramificati on shows a regular trend with injection rate and ce:ll gap, such that the d imensionless perimeter scales with the dimensionless time. By adding defect s to the lattice, we observe increased branching in the pattern morphologie s. However, even in this case, the scaling behavior persists. Only the pref actor of the scaling function shows a dependence on the defect density. For different lattice defect densities, we examine the nature of the different morphology phases. [S1063-651X(99)12508-X].