Unsteady behavior of flow in a scaled-up vocal folds model.
Measurements of the fluid flow through a scaled-up model of the human glottis are presented to determine whether glottal flow may be approximated as unsteady. Time- and space-resolved velocity vector fields from digital particle image velocimetry (DPIV) measurements of the flow through the gap between two moving, rigid walls are presented in four cases, over a range of Strouhal numbers: 0.010, 0.018, 0.035, 0.040, corresponding to life-scale f(0) of 30, 58, 109, and 126 Hz, respectively, at a Reynolds number of 8000. It is observed that (1) glottal flow onset is delayed after glottal opening and (2) glottal flow shutoff occurs prior to closure. A comparison between flow through a fully open, nonmoving glottis and that through the moving vocal folds shows a marked difference in spatial structure of the glottal jet. The following features of the flow are seen to exhibit strong dependence on cycle frequency: (a) glottal exit plane velocity, (b) volume flow, (c) vortex shedding rates, and (d) vortex amplitude. Vortex shedding appears to be a factor both in controlling flow resistance and in cycle-to-cycle volume flow variations. All these observations strongly suggest that glottal flow is inherently unsteady.
Krane
Michael
M
Center for Advanced Information Processing, Rutgers University, Piscataway, New Jersey 08854, USA.
Barry
Michael
M
Wei
Timothy
T
D001696:Biomechanical Phenomena; D005931:Glottis / Q000033:anatomy & histology / Q000502:physiology*; D006801:Humans; D008953:Models, Anatomic; D008954:Models, Biological; D009038:Motion; D010699:Phonation; D011312:Pressure; D012212:Rheology; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D014827:Vocal Cords / Q000033:anatomy & histology / Q000502:physiology*