Solid particles focusing, orienting, and de‐focusing in planar Poiseuille flow

Three‐dimensional, time‐dependent lattice‐Boltzmann simulations of neutrally buoyant particles in planar Poiseuille flow have been performed. The particles are spherical or cylindrical (the latter with a length over diameter ratios in the range 1/3 to 2) and have volume fraction ranging from virtually zero (one particle) to 0.15. The channel's Reynolds number is in the range of 15 to 150. We first show agreement with earlier studies for single particle behavior in terms of lateral migration and orientation. We then show for the higher solids loadings to what extent particle–particle interactions influence focusing of particles and how—for cylinders—their orientations get distributed. The observed, and often strongly inhomogeneous, particle distributions as well as pronounced orientation distributions have an apparent impact on the flow resistance of the suspensions. We interpret the latter with help of the particle and liquid shear stress profiles over the height of the channel.