“Pulsatile Flow Phenomena in Models of Curved Arteries”

Abstract:

Pulsatile flow, unsteady phenomena, coherent vortical structures, and transitional or turbulent flows
occurring at low Reynolds numbers are common in cardiovascular flows. Examples of pathological
blood flow in which unsteadiness, separation and turbulence are important include regurgitant heart
valves, stenoses or blockages, stents, and arterial branches and bifurcations. The overall goal of our
research program is to understand secondary flow structures in arteries and to assess their potential
impact on vascular health and disease progression. Our overarching motivation for studying
cardiovascular flow is to facilitate evaluation and design of treatment interventions and for surgical
planning, i.e. to enable physicians to assess the outcomes of surgical procedures by using faithful
computer simulations. Experiments were performed using multi-harmonic, physiological, carotid
artery-based inflow conditions (Womersley number = 4.2). A 180-degree curved test section with
curvature ratio (1/7) was used as an idealized, rigid geometry for curved arteries. Our rigid arterial
model is relevant to the aged population and to cardiovascular diseases such as atherosclerosis and
renal artery stenoses that are strongly associated with arterial stiffness. Magnetic resonance
velocimetry (MRV) and particle image velocimetry (PIV) techniques were implemented
independently to investigate evolution of spatio-temporal secondary flow structures. Newtonian blood
analog fluids were used for both MRV and PIV experiments. The MRV-technique offers the
advantage of four-dimensional velocity field acquisition without requiring optical access or flow
tracers. A novel wavelet decomposition-based approach that is autonomous and does not require a
user-set threshold was applied to PIV- and MRV-data to identify and analyze coherent secondary flow
structures. The richness of morphologies and physics of these vortical structures and their formation
and subsequent loss of coherence during deceleration phases suggests implications related to the blood
flow in diseased, stented and stent-fractured conditions. Complementary companion Computational
Fluid Dynamics (CFD) studies were also performed to provide further insight and to reveal wall shear
stress distribution and its relation to the flow structures

Biosketch:

Dr. Michael W. Plesniak is Professor and Chair of the Department of Mechanical & Aerospace Engineering at
the George Washington University. He was formerly Professor of Mechanical Engineering at Purdue University
and Eugene Kleiner Professor for Innovation in Mechanical Engineering at Polytechnic University in Brooklyn,
NY. He served as the Director of the Fluid Dynamics & Hydraulics program at the National Science Foundation
from 2002-2006. Prof. Plesniak earned his Ph.D. degree from Stanford University, and his M.S. and B.S degrees
from the Illinois Institute of Technology; all in Mechanical Engineering. Dr. Plesniak is a Fellow of AIAA,
ASME, the American Physical Society (APS), the American Institute for Medical and Biological Engineering
(AIMBE) and the Association for the Advancement of Science (AAAS). He has authored over two hundred fifty
refereed archival publications, conference papers and presentations. He has presented numerous invited seminars
and keynote addresses. His research group is currently studying the physics of phonation and cardiovascular
flows. Dr. Plesniak is the Director of GW’s Center for Biomimetics and Bioinspired Engineering. Prof. Plesniak
was a recipient of the 2011 NASA DC Space Grant Consortium’s Outstanding STEM Faculty Award, awarded to
faculty that make an outstanding contribution to STEM that goes above and beyond the classroom. Dr. Plesniak
was also named the American Institute for Aeronautics and Astronautics, National Capital Section Engineer of
the Year 2010-2011 for his work on contaminant transport in aircraft, service to the fluid dynamics community
and public policy advocacy.