Session: 04-01-01 Biomedical Fluid Mechanics 1

Paper Number: 183784

183784 - Wall Shear Stress and Oxygen Transport Characteristics in Separated and Reattached Flow Regions of Human Blood 

Abstract: 

Separated flows are frequently encountered in cardiovascular circulatory systems and biomedical applications, e.g. artificial organs, rotary blood pumps, heart valves, stents, catheters, and probes. They are of practical importance and fundamental interest from a fluid mechanics point of view.

The rheological characteristics of blood are of fundamental and clinical interest. Proper characterization of blood rheology is a very critical component in blood flow modeling. Microcirculation and tissue oxygenation are very important factors strongly linked to hemorheology, especially in cardiovascular patients, and their alterations could cause impairment, or initiate cardiovascular pathologies.

Previous hemorheological studies quantified and emphasized the yield stress non-Newtonian characteristic of unadulterated human blood. Hematocrit is one of the major factors determining the blood viscosity at high shear rates while red blood cell aggregation plays a significant role at low shear rates. Yield stress plays a dominant role at low shear rates, typically encountered in separated flow regions. In addition to possessing a yield stress, due to RBC aggregation, human blood was also found to be pseudoplastic or shear-thinning, another non-Newtonian characteristic, i.e., blood is a viscoplastic non-Newtonian fluid. Viscoplastic non-Newtonian rheology was found to have a dramatic impact on the global characteristics of separated and reattached flow regions as well as the extent and intensity of flow recirculation.

This study investigates impacts of the blood rheology model choice and flow constriction on the resulting wall shear stress (WSS) distribution and oxygen transport behavior in separated and reattached flow regions of human blood. Wall-bounded separating flows are encountered in biological applications dealing with blood flows through arteries and prosthetic devices. Separated flow regions have been associated in the past with the most common arterial disease, atherosclerosis. Clinical evidence suggests that local WSS patterns influence the site and the progression of atherosclerotic lesions. The findings of the study will improve our understanding of the mechanisms linking human blood rheology, wall shear stress distributions, and flow and mass transfer behavior to atherosclerosis.

Newtonian and non-Newtonian hemorheological models that account for the yield stress and shear-thinning characteristics of blood are used. Three rheological models of blood will be considered: yield shear-thinning, shear-thinning, and Newtonian. Flow constriction ratios that are representative of moderate to severe stenosis are investigated. The conservation of mass, momentum, and species equations as well as the Herschel-Bulkley constitutive equation are numerically solved using a finite-difference scheme.

Presenting Author: Khaled Hammad Central Connecticut State University

Presenting Author Biography: Prof. Khaled J. Hammad received his Ph.D. degree in Mechanical Engineering from New York University Polytechnic School of Engineering and did his postdoctoral work at the Pacific Northwest National Laboratory. He joined the Department of Engineering at Central Connecticut State University (CCSU) in August 2011 after working more than 12 years for Dantec Dynamics. He chaired the ASME Fluids Engineering Division Executive Committee (2018-2019). His technical expertise and research interests include Laser Diagnostics, Fluid Flow, Heat, and Mass Transfer in Single and Multiphase Systems, Non-Newtonian Fluids, and Energy Conversion Systems. Prof. Hammad is a contributing author to over 95 peer reviewed publications.

Authors:

Khaled Hammad Central Connecticut State University