STABILIZATION MECHANISMS OF SHORT WAVES IN STRATIFIED GAS-LIQUID FLOW

Interfacial waves grow in a cocurrent, stratified gas-liquid flow by e xtracting energy from the main flow. The most unstable mode typically has a wavelength comparable to or less than the liquid depth. Experime nts show that these short waves can saturate at small amplitude with n o generation of long-wave or transverse modes. By decomposing the typi cal Stuart-Landau analysis into three components, it is found that sat uration usually occurs by cubic self-interaction of the fundamental mo de but quadratic resonant interaction with the first overtone is also possible. Interaction with mean flow modes is usually much less import ant. Experiments confirm the predictions of weakly nonlinear theory. T he measured overtone is found to be O(\A(1)\(2)) and is phase-locked w ith the fundamental except near a 1-2 resonance point where the fundam ental and the overtone have comparable speeds. Near this resonance, th e amplitudes are of the same order and the phase angle between them is observed to jump irregularly as predicted by modern dynamical systems theory for intermittent chaos near a heteroclinic cycle. The phase an d magnitude of the overtone interaction specify the shape, chaotic dyn amics and symmetry of the waves across resonance which are analyzed an d confirmed experimentally. (C) 1997 American Institute of Physics.