[Crib-list] COMPUTATIONAL RESEARCH in BOSTON SEMINAR -- Friday, 11/04/2005 (fwd)

[Shirley Entzminger]

 			COMPUTATIONAL RESEARCH IN BOSTON SEMINAR


DATE:		FRIDAY, NOVEMBER 4, 2005
TIME:		12:30 PM
LOCATION:	Building 32, Room 144 (Stata Center)

(Pizza and beverages will be provided.)

TOPIC:	TRANSITIONAL FLOW IN STENOSED CAROTID ARTERY

SPEAKER:  SEUNG E. LEE
  Department of Mechanical Engineering
  Massachusetts Institute of Technology


ABSTRACT:

Patients with severely stenotic arteries are at potential health risks such as 
ischemia, heart attack, and stroke. However, the study of hemodynamics within 
severe stenosis has been limited due to its complex flow nature. A number of 
studies employed numerical and experimental tools to study the transitional 
nature of the blood using simplifying assumptions (idealized geometries, 
turbulence model, or 2D model), and significant insights have been gained from 
them. Nevertheless, it is evidently clear from these reports that the use of 
the patient-specific flow conditions and geometries are essential in order to 
fully characterize the three-dimensional nature of the post-stenotic 
transitional flow, which can possibly help evaluate the patient-specific 
vulnerability from the determined flow pattern. In this paper, we report a 
direct numerical simulation result of the transitional flow in 
patient-specific-severely-stenosed carotid bifurcation using flow conditions 
obtained directly from the patient as the boundary conditions. The Spectral 
Element Method (SEM) software used for this study has been previously validated 
through comparison with experimental results of transitional flows.

Two sites of high frequency vortex shedding were observed during the 
deceleration phase of the systole. One vortex shedding was located downstream 
of the stenosis, and the other was located right in the stenosis, which broke 
off from the apex. The vortex shedding frequency was within the audible range, 
which the physicians listen for in search of stenosis-induced turbulence in 
their simple non-invasive diagnosis. The throat of the stenosis was subjected 
to very high shear stress, which was suggested to cause plaque rupture or 
platelet activation. Oscillatory flow reversal and low pressure were observed 
just distal of the stenosis, which may fatigue the calcified plaque or cause 
the formation of the thrombosis. This study provides a quantitative means of 
characterizing the post-stenotic flow field, and may help elucidate the 
mechanistic insights of plaque vulnerability.


Massachusetts Institute of Technology
Department of Mathematics
Cambridge, MA  02139


http://www-math.mit.edu/crib

For information on CRiB, contact:
Alan Edelman:  edelman at math.mit.edu
Steven G. Johnson:  stevenj at math.mit.edu
Jeremy Kepner:  kepner at ll.mit.edu