Affiliations: Department of Mechanical Engineering, University of Calgary, Calgary, AB, Canada
Note: [] Address for correspondence: PhD Andrew Walker, Department of Mechanical Engineering, University of Calgary, 2500 University Dr. N.W., Calgary, Alberta, Canada, T2N 1N4. Tel.: +1 403 210 7593; Fax: +1 403 282 8406; E-mail: walkeram@ucalgary.ca
Abstract: BACKGROUND: Although a blood analog of aqueous glycerol and xanthan gum was found to replicate the viscoelastic behavior of blood, measurements were restricted to laminar flow. OBJECTIVE: To expand the characterization of a non-Newtonian blood analog of aqueous glycerol and xanthan gum to transitional Reynolds numbers to quantify its behavior as a function of both natural and shear-layer-induced mechanisms. METHODS: A Newtonian analog and a shear-thinning aqueous glycerol, xanthan gum solution were circulated through an in vitro flow loop replicating both a straight and obstructed artery where transition was initiated through natural and shear-layer-induced mechanisms respectively. Steady and pulsatile pressure drop measurements for both fluids were acquired across a range of Reynolds numbers up to 7600 and Womersley numbers of 4 and 6. RESULTS: In steady and pulsatile straight flow, the non-Newtonian analog presented with reduced pressure drops and prolonged laminar flow to Reynolds numbers of 3200 and 3800 respectively. Upon blockage inclusion, non-Newtonian minor losses were comparable to Newtonian in steady flow and greater in pulsatile flow suggesting an elongation of downstream non-Newtonian recirculation. Although non-Newtonian total system pressure drops in both straight and obstructed flows were lower, the ratio of pressure drop difference between the two fluids decreased through shear-layer-induced transition. CONCLUSIONS: These findings not only demonstrated the suitability of using a xanthan gum analog to model blood flow in transitional regimes, but also presented the respective differences in analog behavior as a function of transition mechanism.
Keywords: Blood analog fluids, viscoelastic fluids, natural transition, shear-layer-induced transition
DOI: 10.3233/BIR-14009
Journal: Biorheology, vol. 51, no. 4-5, pp. 275-291, 2014
