The distribution of red blood cells (RBCs) in a confined channel flow is inhomogeneous and shows a marked depletion near the walls due to a competition between migration away from the walls and shear-induced diffusion resulting from interactions between particles. We investigated the lift of RBCs in a shear flow near a wall and measured a significant lift velocity despite the tumbling motion of cells. We also provide values for the collective and anisotropic shear-induced diffusion of a cloud of RBCs, both in the direction of shear and in the direction of vorticity. A generic down-gradient subdiffusion characterized by an exponent 1/3 is highlighted.

The current paper aims to provide numerical and experimental flow data relevant for physical modelling of human fricative sound production due to the interaction of airflow with the teeth. A simplified upper incisor-palate geometry is derived from typical morphological features. The geometry is inserted in a rectangular channel for which the width-to-height ratio yields 4. The obstruction degree due to the presence of the simplified upper incisor yields 70%. Numerical flow data are obtained from large eddy simulations. Experimental flow data are gathered from single-sensor anemometry on a rigid plaster print of the computational grid. Transverse velocity profiles are obtained downstream in the constricted area, i.e., from x = 0 up to x/h = 1.5 with h denoting the aperture height. The Reynolds number is set to 4000. The mean velocity profiles derived on simulated and measured data exhibit a strong asymmetry due to the presence of the obstruction. Nevertheless, significant differences appear with respect to the jet development, as e.g., quantified by the downstream evolution of the jet width or the appearance of significant turbulence intensities (>10%) at the teeth edge in the measured data whereas the simulated flow remains laminar.