Tanaka G, Ueda Y, Tanishita K
Institute of Biomedical Engineering, Faculty of Science and Technology, Keio University, Yokohama, Japan.
J Biomech Eng. 1998 Jun;120(3):405-15. doi: 10.1115/1.2798008.
The efficiency of axial gas dispersion during ventilation with high-frequency oscillation (HFO) is improved by manipulating the oscillatory flow waveform such that intermittent oscillatory flow occurs. We therefore measured the velocity profiles and effective axial gas diffusivity during intermittent oscillatory flow in a straight tube to verify the intermittency augmentation effect on axial gas transfer. The effective diffusivity was dependent on the flow patterns and significantly increased with an increase in the duration of the stationary phase. It was also found that the ratio of effective diffusivity to molecular diffusivity 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 times as large, thereby proving that the use of intermittent oscillatory flow effectively augments axial dispersion for ventilation with HFO.
通过操控振荡流波形使间歇性振荡流出现，可提高高频振荡（HFO）通气期间轴向气体弥散的效率。因此，我们测量了直管中间歇性振荡流期间的速度剖面和有效轴向气体扩散率，以验证间歇性增强对轴向气体传输的影响。有效扩散率取决于流动模式，并随着静止期持续时间的增加而显著增加。还发现，有效扩散率与分子扩散率之比比正弦振荡流中的大两倍。此外，减速期间或静止期开始时的湍流进一步增强轴向弥散，有效扩散率超过三倍大，从而证明使用间歇性振荡流可有效增强HFO通气的轴向弥散。
