论文标题
锥形几何形状中复杂流体的粘性指法不稳定
Viscous Fingering Instability of Complex Fluids in a Tapered Geometry
论文作者
论文摘要
储层计算是预测湍流的有力工具，其简单的架构具有处理大型系统的计算效率。然而，其实现通常需要完整的状态向量测量和系统非线性知识。我们使用非线性投影函数将系统测量扩展到高维空间，然后将其输入到储层中以获得预测。我们展示了这种储层计算网络在时空混沌系统上的应用，该系统模拟了湍流的若干特征。我们表明，使用径向基函数作为非线性投影器，即使只有部分观测并且不知道控制方程，也能稳健地捕捉复杂的系统非线性。最后，我们表明，当测量稀疏、不完整且带有噪声，甚至控制方程变得不准确时，我们的网络仍然可以产生相当准确的预测，从而为实际湍流系统的无模型预测铺平了道路。
Viscous fingering (VF) is an interfacial instability that occurs in a narrow confinement or porous medium when a less-viscous fluid pushes a more viscous one, producing finger-like patterns. Controlling the VF instability is essential to enhance the efficiency of various technological applications. However, the control of VF instability has been challenging and so far focused on simple Newtonian fluids of constant viscosity. Here, we extend to complex yield-stress fluids and examine the controlling feasibility by carrying out a linear stability analysis using a radial cell with a converging gap gradient. We avoid making the major assumption of a small Bingham number, Bn << 1, i.e., a negligible ratio of the yield to shear stress, and instead provide a new stability criterion predicting apparent complex VF. This criterion depends on not only the complex fluid's rheology, interfacial tension, and contact angle to the wetting wall, but also the gap gradient, the radius, gap-thickness, and velocity at the fluid-fluid interface. Finally, we compare this theoretical criterion to our experimental data with nitrogen pushing a complex yield-stress fluid in a taper and find good agreement.
