Understanding of pore scale displacement processes for Newtonian and complex fluids through the interaction of fluid properties and pore geometry.

该项目的目的是了解非牛顿流体在多孔介质(微流体模型系统)中的驱替行为。这种驱替行为是由(复杂的)流体性质(如润湿性、剪切速率相关的粘度和弹性)以及几何参数(如流道的大小和形状)的相互作用决定的。剪切速率相关的流体性质会导致恒定(全局)体积流量下非均质多孔介质内粘度分布的“几何相关”，以及局部弹性效应。为了了解复杂流体性质对孔隙尺度不稳定性的影响，从而对整体驱替行为的影响，我们将比较复杂流体的整体驱替行为和局部驱替行为，以及具有相同零剪切粘度的牛顿流体的驱替行为。应通过确定流场来估计发生的与几何形状相关的局部剪切率以及由此产生的局部粘度。实验将在不同的孔隙空间几何形状和不同的流速下进行，包括润湿和非润湿的侵入(复杂)流体。速度的选择方式是毛细作用力、粘性作用力和可能的弹性作用力占主导地位，而惯性作用力可以忽略。通过使用两个不同放大倍率的相机，可以同时观测到整体位移图案和快速的局部弯月面不稳定性。通过数值图像分析确定不同局部失稳的频率，并用来解释导致不同整体位移模式的不同位移模式。全局模式将通过各种统计描述符来量化，例如手指宽度。通过比较所有获得的数据，可以确定剪切稀化粘性和弹性对某些局部不稳定性的发生以及最终对整体位移行为的润湿影响。

The aim of this project is to understand the displacement behavior of non-Newtonian fluids in porous media (microfluidic model systems). This displacement behavior is determined by the interplay of (complex) fluid properties such as wettability, shear rate dependent viscosity and elasticity as well as geometric parameters such as size and shape of flow channels. The shear rate dependent fluid properties can lead to a "geometry dependent" viscosity distribution within a heterogeneous porous medium at a constant (global) volume flow, as well as to local elasticity effects. In order to understand the influence of complex fluid properties on the pore-scale instabilities and hence on the global displacement behavior, the global and local displacement behavior of the complex fluids will be compared with each other, as well as with the displacement behavior of Newtonian fluids with the same zero shear viscosity. The occurring geometry-dependent local shear rates and thus local viscosities shall be estimated by determining the flow fields. The experiments will be carried out for different pore space geometries and different flow velocities, for both wetting and a non-wetting invading (complex) fluids. The velocities are chosen in such a way that capillary, viscous and possibly elastic forces dominate, while inertial forces can be neglected. By using two cameras with different magnification optics, the global displacement patterns as well as the fast local meniscus instabilities will be observed simultaneously. The frequency of different local instabilities will be determined by numerical image analysis and used to explain the different displacement modi that lead to different global displacement patterns. The global patterns will be quantified by various statistical descriptors such as finger width. By comparing all the data obtained, the wetting-dependent influence of shear-thinning viscosity and elasticity, respectively the combination of both non-Newtonian properties, on the occurrence of certain local instabilities and thus ultimately on the global displacement behavior shall be determined.