Influence of yield stress on the fluid droplet impact control

Influence of the yield stress level and intensity of inertia on the transient and final stages of drops impact were studied. It was shown how the increasing yield stress dictates the drop formation and also led to an emphasis of the inhibition of spreading and the weakening of retraction in the case of high inertial impacts. It was also noticed that the magnitude of the gravitational subsidence observed for the low impact velocities, is governed by the initial non-spherical shape of droplets. Dimensionless numbers were defined in the case of yield stress fluids, allowing us to compare the effects of forces present in the process and better understand the phenomena observed. Wall slip of gels on the PMMA substrate was characterized. Its influence on the drop spreading has been discussed.