Journal of Ultrasound in Medicine, Vol 13, Issue 6 467-472, Copyright © 1994 by American Institute of Ultrasound in Medicine
Development of turbulence in steady flow through models of abdominal aortic aneurysms
R. A. Peattie, T. Schrader, E. I. Bluth and C. E. Comstock
Department of Biomedical Engineering, Tulane University, New Orleans, LA 70118.
As part of a general examination of the effects of blood flow patterns on
the risk of rupture of abdominal aortic aneurysms, we have investigated
steady flow through a series of polyvinyl chloride models of fusiform
aneurysms. A series of steady flow rates between 460 ml/min and 2.0 l/min
have been delivered through the models, and the resulting flow patterns
have been evaluated by color Doppler flow imaging. At low volume flow
rates, the pattern of flow through the model is smooth and laminar. At
higher flow rates, however, this is replaced by an irregular, fluctuating,
and apparently turbulent motion. This finding is consistent with previous
clinical observations. Turbulence appears initially at the distal end of
the model aneurysm and then spreads proximally to fill the whole model only
if the flow rate continues to increase. The onset of irregular, turbulent
flow is found to be governed by both the overall flow rate through the
model and the model diameter. Critical conditions for the appearance of
turbulence are presented and discussed, and the critical value of the
Reynolds number for both the initial distal transition and the final full
transition is shown to decrease as the size of the model aneurysm
increases.
