Propriétés rhéologiques et écoulement dans des microcanaux de suspensions de microalgues. A detailed characterization of plane micro-channel flows of Chlorella suspensions with various volume fractions in a wide range of driving pressures drops reveals flow

Colloque avec actes et comité de lecture. Internationale.International audienceA systematic study of the rheological properties of solutions of non-motile microalgae (Chlorella vulgaris CCAP 211-19) in a wide range of volume fractions is presented. As the volume fraction is gradually increased, several rheological regimes are observed. At low volume fraction the suspension display a Newtonian rheological behavior. For intermediate values of the volume fraction a shear thinning behaviour is observed. For the largest values of the volume fraction investigated an apparent yield stress behaviour is observed. Increasing and decreasing stress ramps within this range of volume fraction indicate a thixotropic behaviour as well. To gain a deeper insight into the emergence of the shear thinning and yield stress regimes, the microscopic organization of individual cells is observed simultaneously with the macroscopic rheological measurements. Thus, the emergence of the shear thinning behavior is explained by the presence of flocs of individual cells and the yield stress behavior is explained by the formation of large scale cell aggregates which behave like rigid plugs. A detailed characterization of plane micro-channel flows of Chlorella suspensions with various volume fractions in a wide range of driving pressures drops reveals flow patterns consistent with the rheological regimes observed during the macroscopic rheological measurements