AUGMENTATION OF AXIAL-DISPERSION BY INTERMITTENT OSCILLATORY FLOW

The efficiency of axial gas dispersion during ventilation with high-fr equency oscillation (HFO) is improved by manipulating the oscillatory flow waveform such that intermittent oscillatory flow occurs. We there fore measured the velocity profiles and effective axial gas diffusivit y during intermittent oscillatory flow in a straight tube to verify, t he intermittency augmentation effect on axial gas transfer The effecti ve diffusivity was dependent on the flow patterns and significantly in creased with an increase in the duration of the stationary phase. It w as also found that the ratio of effective diffusivity to molecular dif fusivity is two times greater than that in sinusoidal oscillatory flow . Moreover, turbulence during deceleration or at the beginning of the stationary phase further augments axial dispersion, with the effective diffusivity being over three limes as large, thereby proving that the use of intermittent oscillatory flow effectively augments mini disper sion for ventilation with HFO.