Objectives:
To understand the behavior of concentrated nanosuspensions and capillary nanosuspensions under the conditions of high extensional and shear rates.
Expected Results:
– Evolution of liquid bridge shape as a function of time and strain rate
– The rheological properties from the elongation and breakup of liquid drops
– Comparison with the measurement results in WP1 and WP3 of nanoPaInt
– Pinch-off dynamics, such as time and length
– Dynamics of dewetting and fingering instabilities
Samples tested:
1. Newtonian liquids
2. Nanofluids
3. Dense nanosuspensions
4. Nanoemulsions
5. Capillary nanosuspensions
- Extensional Rheology and Dewetting of Nanosuspensions
The stretching of a liquid bridge is governed by inertia and the internal stresses which are determined by the liquid rheological properties. Some details on the flow, breakup, and flow instabilities can be found in our publications [1],[2][3]. A liquid bridge stretching setup capable of accelerating up to 20G is built specifically for this project. The phenomena are very fast and often fascinating.
A recent review article titled “Forced flows in liquid bridges” is now available for open access in the journal of Current Opinion in Colloid and Interface Science.
- Drop Impact Viscometry (DIV): Drop Impact on a Spherical Target
A novel method to measure viscosity has been developed by ESR05 using drop impact on a spherical target shown in the sketch below. It relies on high-speed imaging and analysis of the fluid mechanics using a theory developed specifically for this problem. A water drop impact example is shown in the video below. The method is currently being upgraded to study nanosuspensions and nanoemulsions.
- Effect of nanoparticles on the splashing of nanofluids
Liquid droplet splashing on various surfaces, including complex ones, is a widely studied topic in fluid mechanics. Recently, there has been growing interest in using nanofluids, which are created by adding nanoparticles to regular fluids, for applications like spray cooling. Despite the fact that a small nanoparticle addition doesn’t alter the fluid’s viscosity, it has a significant effect on splashing behavior. This means that we need to combine insights from studying nanosuspension rheology with this complex problem, as we deal with a seemingly simple material in a complex flow.
ESR05 is on a mission to explore the role of nanoparticles in the elongation and breakup of drops during the splashing of nanofluids. Below is a preliminary results video of a nanofluid drop splashing on a flat smooth surface. More details are published in the initial perspective paper “Role of Nanoparticles in Nanofluid Droplet Impact on Solid Surfaces” in Langmuir.