Mixing and transport of particles and droplets co-suspended in a liquid-continuous phase

每天我们都会遇到含有液滴和粒子的系统。喷墨打印机需要两者的结合；沙拉酱或酸奶等许多食品的口感和稳定性也依赖于它们，许多药物的制备也是如此。在这些情况下，颗粒相对于液滴的大小非常小，因此它们聚集在液滴表面，形成使液滴高度稳定的“盔甲”。在粒子比液滴大的情况下，系统的行为可能完全不同，实际上还不能很好地预测。在涉及流动或混合的系统中尤其如此。一些不同的例子包括混合/反应过程，它为我们提供了许多我们使用的常见塑料，以及在生产含有水滴和沙子的原油中。在某些条件下，颗粒有助于液滴的分解，即液滴将比无固体条件下的液滴小。这可能会使将液滴与携带液滴的液体分离变得更加困难。此外，液滴的存在会使颗粒的运输变得更加困难，无论是在所需的能量方面，还是在阻止它们沉淀的能力方面。颗粒聚集会导致管道腐蚀和失效，因为沉淀后的颗粒会将水困在管壁附近。目前，对液滴和较大颗粒之间的相互作用进行建模--甚至理解--的能力极其有限。一个问题是，几乎没有人对这些系统进行过基础研究。此外，尽管人们很好地理解了液滴单独的行为或单独沉淀颗粒的行为，但两者的组合似乎并不遵循相同的规则。这项研究计划旨在解决一些关键的知识差距。在短期内，目标是确定(1)液滴的存在如何影响颗粒的沉降特性，以及(2)颗粒的存在如何引起液滴尺寸的变化。在一系列实验中，相同的液滴和颗粒系统将在管流、定制的剪切单元(两个同心圆筒，通过旋转内筒产生流动)和混合罐中进行测试。在每种情况下，都将测量有和没有液滴使颗粒悬浮所需的功率。将进行第二系列测试，测量添加到混合物中的能量(考虑罐中的混合速度或管道中的速度)、颗粒大小和浓度对液滴大小的影响。最终目标是建立颗粒沉降和液滴大小的模型，该模型将适用于任何类型的混合或运输过程。广泛的行业都需要这些成果：例如更清洁、更节能的石油生产和精炼工艺，以及从植物中生产生物燃料。

Every day we encounter systems containing droplets and particles. The combination of the two is needed for inkjet printers; the mouth-feel and stability of many food products, like salad dressing or yogurt also depend on them, as does the preparation of many medicines. In these cases, the particles are very small relative to the size of the droplets, so they collect on the droplet surfaces, forming "suits of armour" that make the droplets highly stable. In cases where the particles are larger than the droplets, the behaviour of a system can be totally different, and in fact cannot yet be well predicted. This is especially true in a system where flow or mixing is involved. Some diverse examples include the mixing/reaction process that provides us with many of the common plastics we use, and in the production of crude oil containing water droplets and sand. Under some conditions, the particles contribute to droplet break-up, i.e. the droplets will be smaller than they would be under solids-free conditions. This can make it much more difficult to separate the droplets from the liquid that carries them. Also, the presence of the droplets can make it more difficult to transport the particles, both in terms of the energy required and the ability to keep them from settling. Particle accumulation can lead to pipeline corrosion and failure, since the settled particles trap water near the pipe wall. Currently, the ability to model - or even to understand - the interactions among droplets and larger particles is extremely limited. One problem is that almost no fundamental research has been done on these systems. Also, despite the fact that the behaviour of droplets alone or settling particles alone is reasonably well understood, the combination of the two does not seem to follow the same rules. This research program is designed to address some key knowledge gaps. In the short term, the goal is to determine (i) how the presence of the droplets affects the settling characteristics of the particles and (ii) how the presence of the particles produces changes in the droplet sizes. In one series of experiments, identical systems of droplets and particles will be tested in a pipe flow, a custom-built shearing cell (two concentric cylinders, with flow between them produced by rotating the inner cylinder) and in a mixing tank. In each case the power needed to suspend the particles with and without droplets will be measured. A second series of tests will be conducted where the effects of energy added to the mixture (think mixing speed in a tank or velocity in a pipe), particle size and concentration on droplet size will be measured. The ultimate goal is to produce models of particle settling and droplet size, which would apply to any type of mixing or transportation process. The results are needed in a wide range of industries: examples include cleaner, more energy efficient processes for oil production and refining, and to produce biofuels from plants.