Diving into shear-thickening
| When |
Oct 05, 2021
from 03:00 to 04:00 |
|---|---|
| Where | Online |
| Attendees |
Philippe Bourrianne |
| Add event to calendar |
vCal
iCal
|
Colloidal suspensions are ubiquitous in our daily life. Micrometric particles dispersed in a solvent are indeed present in common liquids such as paints, inks or even food products. Colloidal suspensions exhibit a wide range of rheological behaviors from shear-thinning to yield stress fluids.
By dispersing fumed silica particles into polypropylene glycol, we obtain a model suspension exhibiting a variety of controllable rheological regimes from shear-thinning, yield stress to shear-thickening at low volume fraction due to the geometry of the particles. We will describe how particle surface roughness and chemistry affect the rheology of the suspension. We will specifically show how we can tune the shear-thickening transition and thus understand the interactions involved in this behavior.
Due to this enhanced dissipation under high stress, shear-thickening fluids are known for their remarkable ability to absorb energy during collisions. When a solid object impacts a bath of shear-thickening fluid, the initial velocity determines the different settling regimes that are observed. We will describe these different regimes in relation to the rheological properties of the shear-thickening liquid and the characteristics of the impacting object. A few surprising observations could be noticed. First, a high velocity is not always the best way to penetrate such suspensions. Under such conditions, an appropriately-shaped fast-moving object can also bounce during the impact due to the shear-thickening behavior. By comparing the deceleration of an object into a viscous Newtonian and a shear-thickening liquid, we will explain the spectacular properties of shear-thickening during a collision.