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Modeling blood flow in larger vessels using lattice-Boltzmann methods comeswith a challenging set of constraints: a complex geometry with walls andinlet/outlets at arbitrary orientations with respect to the lattice,intermediate Reynolds number, and unsteady flow. Simple bounce-back is one ofthe most commonly used, simplest, and most computationally efficient boundaryconditions, but many others have been proposed. We implement three othermethods applicable to complex geometries (Guo, Zheng and Shi, Phys Fluids(2002); Bouzdi, Firdaouss and Lallemand, Phys. Fluids (2001); Junk and YangPhys. Rev. E (2005)) in our open-source application \HemeLB{}. We use these tosimulate Poiseuille and Womersley flows in a cylindrical pipe with an arbitraryorientation at physiologically relevant Reynolds (1--300) and Womersley (4--12)numbers and steady flow in a curved pipe at relevant Dean number (100--200) andcompare the accuracy to analytical solutions. We find that both theBouzidi-Firdaouss-Lallemand and Guo-Zheng-Shi methods give second-orderconvergence in space while simple bounce-back degrades to first order. The BFLmethod appears to perform better than GZS in unsteady flows and issignificantly less computationally expensive. The Junk-Yang method shows poorstability at larger Reynolds number and so cannot be recommended here. Thechoice of collision operator (lattice Bhatnagar-Gross-Krook vs.\ multiplerelaxation time) and velocity set (D3Q15 vs.\ D3Q19 vs.\ D3Q27) does notsignificantly affect the accuracy in the problems studied.

Choice of boundary condition for lattice-Boltzmann simulation of moderate Reynolds number flow in complex domains