The flow features in branching networks are fundamental for the understanding of transport processes in respiratory and cardiovascular systems. Specifically for tumor embolization, the ability to predict the fate of finite-size particles in bifurcating vessels is highly desirable for improving embolization efficacy. Most past studies focused on very dilute regimes in which particles are not expected to interact with each other. In the present study, we use particle tracking velocimetry to investigate the spatial distribution, velocity, acceleration, and dispersion of finite-size particles in a four-generation bifurcating model. We consider a regime especially relevant to vascular embolization: a physiologic range of bulk flow Reynolds number and a suspension of neutrally buoyant particles with a diameter about 10 times smaller than the parent vessel diameter, reaching solid volume fractions up to 2%. We investigate how particles distribute among the distal branches and the influence of the release location. In addition, the effect of particle volume fraction is studied through Lagrangian statistics of the particle trajectories. Our results show the remarkable influence of particle concentration on particle transport in several ways. The particle traveling speed, acceleration, and dispersion are inhibited by the increasing particle volume fraction due to interparticle interactions. Importantly, the particles travel preferentially to the medial branches rather than to the lateral ones despite the uniform distribution of the distal volumetric flow rate. The findings provide insights relevant to the optimization of targeted drug delivery in embolization settings.

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• Biological fluid dynamics
• Multiphase flows
• Particle-laden flows
• Physiological flows