Dynamic scaling behavior of a growing self-affine fractal interface in a paper-towel-wetting experiment

The dynamic scaling behavior of a growing self-affine fractal interface is examined in a simple paper-towel-wetting experiment. A sheet of plain white paper towel is wetted with red food dye solution, and the evolution of the interface is photographed with a 35-mm camera as a function of time. Each snapshot is scanned and digitized to obtain the interface height h(x,t) as a function of time and position. From these the interface width w(L,t) is determined as a function of time t and system size L. It is found that the interface width scales with system size L as w(L,t)∼${\mathit{L}}^{\mathrm{\alpha }}$ with α=0.67±0.04 and scales with time as w(L,t)∼${\mathit{t}}^{\mathrm{\beta }}$ with β=0.24±0.02. It is also found that average height of the interface scales with time as 〈h〉∼${\mathit{t}}^{\mathrm{\delta }}$ with δ=0.33±0.02. These results are assessed in comparison with the predictions of theoretical models and the results of other relevant experiments. © 1996 The American Physical Society.