We have studied the flow induced by a macroscopic spherical particle sett領(lǐng) in a Laponite suspension that exhibits a yield stress, thixotropy, and shear thinning. We show that the fluid thixotropy or aging induces an increase with time of both the apparent yield stress and shear-thinning properties but also a breaking of the flow fore-aft symmetry predicted in Hershel-Bulkley fluids yield-stress, shear-thinning fluids with no thixotropy. We have also varied the stress exerted by the particles on the fluid by using particles of different densities. Although the stresses exerted by the particles are of the same order of magnitude, the velocity field presents utterly different features: whereas the flow around the lighter particle shows a confinement similar to the one observed in shear-thinning fluids, the wake of the heavier particle is characterized by an upward motion of the fluid negative wake, whatever the fluids age. We compare the features of this negative wake to the one observed in viscoelastic shear-thinning fluids polymeric or micelle solutions. Although the flows around the two particles strongly differ, their sett領(lǐng) behaviors display no apparent difference which constitutes an intriguing result and evidences the complexity of the dependence of the drag factor on flow field. 德國LaVision PIV/PLIF粒子成像測速場儀 Imager pro X PIV相機 用于粒子成像測速(PIV)的熒光示蹤粒子