Highlights• Systematic analysis of a LB-IB model for arbitrarily shaped particle.• The model is validated towards benchmark numerical results.• The near wall dynamics of a single particle in linear laminar flow is analysed.• The effect of particle shape on the angular velocity distribution is analysed. AbstractModelling the vascular transport and adhesion of man-made particles is crucial for optimizing their efficacy in the detection and treatment of diseases. Here, a Lattice Boltzmann and Immersed Boundary methods are combined together for predicting the near wall dynamics of particles with different shapes in a laminar flow. For the lattice Boltzmann modelling, a Gauss-Hermite projection is used to derive the lattice equation; wall boundary conditions are imposed through the Zou-He framework; and a moving least squares algorithm accurately reconstructs the forcing term accounting for the immersed boundary. First, the computational code is validated against two well-known test cases: the sedimentation of circular and elliptical cylinders in a quiescent fluid. A very good agreement is observed between the present results and those available in the literature. Then, the transport of circular, elliptical, rectangular, square and triangular particles is analyzed in a Couette flow, at Re=20. All particles drifted laterally across the stream lines reaching an equilibrium position, independently of the initial conditions. For this large Reynolds number, the particle shape has no significant effect on the final equilibrium position but it does affect the absolute value and periodicity of the angular velocity. Specifically, elongated particles show longer oscillation periods and, most interestingly, larger variations in angular velocity. The longest particles exhibit a zero angular velocity for almost the whole rotational period. Collectively, this data demonstrates that the proposed approach can be efficiently used for predicting complex particle dynamics in biologically relevant flows. This computational strategy could have significant impact in the field of computational nanomedicine for optimizing the specific delivery of therapeutic and imaging agents.

Modeling the transport of deformable capsules under different flow regimens is crucial in a variety of fields, including oil rheology, blood flow and the dispersion of pollutants.The aim of this study is twofold. Firstly, a combined Lattice Boltzmann -Immersed Boundary (LBM -IB) approach is developed for predicting the transport of inertial deformable capsules. A Moving Least Squares (MLS) scheme has been implemented to correlate the pressure, velocity and force fields of the fluid domain with the capsule dynamics. This computational strategy has been named LBM -Dynamic IB. Secondly, this strategy is directly compared with a more conventional approach, named LBM -Kinematic IB, where capsules move with the same velocity of the surrounding fluid.Multiple test cases have been considered for assessing the accuracy and efficiency of the Dynamic over Kinematic IB scheme, including the stretching of circular capsules in shear flow, the transport in a plane Poiseuille flow of circular and biconcave capsules, with and without inertia. By monitoring the capsule geometry over time, the two schemes have been documented to be in excellent agreement, especially for low Capillary numbers (Ca ≤ 10 -2 ), in the case of non-inertial capsules. Despite a moderate increase in computational burden, the presented LBM -Dynamic IB scheme is the sole capable of predicting the dynamics of both non-inertial and inertial deformable capsules.The proposed approach can be efficiently employed for studying the transport of blood cells, cancer cells and nano/micro capsules within a capillary flow. 3 INTRODUCTIONThe coupling between fluid and structure dynamics is of great relevance in different disciplines. Biophysicists are investing increasingly more efforts into modeling the flow of complex fluids, such as whole blood, to better understand the mechanisms underlying the development of diseases and their possible cure. [1][2][3][4] In a wide range of engineering problems, there is a growing demand to investigate the rheology of active fluids, oils, polymeric suspension, or colloidal mixtures moving into tortuous channels, with either fixed or variable geometries. This is specifically the case of enhanced oil recovery, trickle bed reactors, and microfluidics devices. [5][6][7][8][9][10][11][12] Regardless of the application, it is easy to recognize that immersed structures may be dragged away downstream by large distances, far from their original locations, or significantly deformed due to an incoming flux. On this premise, it is crucial to have access to computational tools capable of efficiently handle the variation in time of immersed geometries without any loss of accuracy. [13][14][15][16] One of the most suitable computational technique to deal with the motion and deformation of particles into fluids is the Immersed Boundary (IB) method, which was originally developed by Peskin in 1972 to simulate cardiac mechanics [17]. This technique prescribes the evolution of the fluid on an Eulerian Cartesian grid, which is not conforming to the geomet...

dynamics of particles with arbitrary geometries and surface properties and represents a fundamental tool in the rational design of particles for the specific delivery of therapeutic and imaging agents.