THE EFFECT OF FLUID DECOUPLING ON VISCOUS MIXING

Flow in a three-dimensional channel with a sinusoidally-wavy, vertical wall is examined for the case of applied down- and cross-channel velo city components. An important parameter for the analysis of the nature of laminar mixing in the flow field occurs when the changes in the do wnstream direction can be decoupled from the changes in the cross-chan nel direction, thereby allowing for a two-dimensional solution of the system of equations. This paper shows the effect on the nature of lami nar mixing when the decoupling of the momentum equations from a fully three-dimensional case to one where a two-dimensional solution can be performed. Experiments are performed on a channel with sinusoidally va rying vertical walls that cover the range of decoupling criteria. Sili cone pigmented either white or black was run in the apparatus, cured, and cross-sectioned. The cross sections embody a local, detailed histo ry of the state of mixing as it proceeds down the mixer. The amount of mixing is presented as a function of position at each cross section f or the different channel configurations. The nature of mixing changes from a linear growth rate in the amount of interfacial area to an expo nential rate as the amplitude of the wave is increased. Results demons trate the existence of chaos, islands, and the factors affecting the m ixing behavior.