title: A unified method for estimating pressure losses at vascular junctions.
abstract: In reduced-order (0D/1D) blood or respiratory flow models, pressure losses at junctions are usually neglected. However, these may become important where velocities are high and significant flow redirection occurs. Current methods for estimating losses rely on relatively complex empirical equations that are only valid for specific junction geometries and flow regimes. In pulsatile multi-directional flows, switching between empirical equations upon reversing flow may introduce unrealistic discontinuities in simulated haemodynamic waveforms. Drawing from work by Bassett et al. (SAE Trans 112:565-583, 2003), we therefore developed a unified method (Unified0D) for estimating loss coefficients that can be applied to any junction (i.e. any number of branches at any angle) and any flow regime. Discontinuities in simulated waveforms were avoided by extending Bassett et al.'s control volume-based method to incorporate a 'pseudodatum' supplier branch, an imaginary effective vessel containing all inflow to the junction. Energy exchange between diverging flow streams was also accounted for empirically. The formulation was validated using high resolution computational fluid dynamics in a wide range flow conditions and junction configurations. In a pulsatile 1D simulation exhibiting transitions between four different flow regimes, the new formulation produced smooth transitions in calculated pressure losses.
authors.affiliation: Biomedical Simulation Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.|Heart Research, Clinical Sciences, Murdoch Childrens Research Institute, Parkville, VIC, Australia.|Department of Paediatrics, University of Melbourne, Parkville, VIC, Australia.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Mynard
authors.affiliation: Biomedical Simulation Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada.|Center for Biomedical Computing, Simula Research Laboratory, Lysaker, Norway.
authors.forename: Kristian
authors.initials: K
authors.lastname: Valen-Sendstad
mesh_terms: D000465:Algorithms; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D003198:Computer Simulation; D008955:Models, Cardiovascular; D011673:Pulsatile Flow / Q000502:physiology*
keywords: bifurcation; blood flow; loss coefficient; lumped parameter model; one-dimensional model; respiratory flow