title: The characterization of a non-Newtonian blood analog in natural- and shear-layer-induced transitional flow.
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.
authors.affiliation: Department of Mechanical Engineering, University of Calgary, Calgary, AB, Canada.
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Mechanical Engineering, University of Calgary, Calgary, AB, Canada.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Walker
authors.affiliation: Department of Mechanical Engineering, University of Calgary, Calgary, AB, Canada.
authors.forename: David E
authors.initials: DE
authors.lastname: Rival
mesh_terms: D001783:Blood Flow Velocity; D001809:Blood Viscosity; D004548:Elasticity; D005990:Glycerol / Q000737:chemistry; D006801:Humans; D008955:Models, Cardiovascular; D011135:Polysaccharides, Bacterial / Q000737:chemistry; D011673:Pulsatile Flow / Q000502:physiology*; D012212:Rheology / Q000379:methods; D013314:Stress, Mechanical; D014783:Viscosity
chemical_list: D011135:Polysaccharides, Bacterial; D005990:Glycerol; C002563:xanthan gum
keywords: Blood analog fluids; natural transition; shear-layer-induced transition; viscoelastic fluids