Reflecting Travelling Waves at the Onset of Oscillatory Convection in Ethanol/Water Mixtures

Recently Cross has proposed that the oscillatory transients seen at the onset of convection in binary fluid mixtures can be explained in terms of convective rolls which travel across the experimental cell, growing exponentially as they move, and which are reflected with loss from the cell walls. By varying the length of our convection cell, we have tested several predictions of this theory. We find that the exponential growth length is proportional to the cell length L and that the temperature difference at the onset of convection has a component which is inversely proportional to L. The amplitude of this effect is in quantitative agreement with the theory. We also launch pulses of oscillatory convection, which are observed to travel back and forth across the cell.