Pajic-Lijakovic Ivana, Milivojevic Milan, McClintock Peter V E
Faculty of Technology and Metallurgy, Department of Chemical Engineering, University of Belgrade, Belgrade, Serbia.
Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK.
J Biol Eng. 2024 Apr 8;18(1):24. doi: 10.1186/s13036-024-00415-6.
Inertial effects caused by perturbations of dynamical equilibrium during the flow of soft matter constitute a hallmark of turbulence. Such perturbations are attributable to an imbalance between energy storage and energy dissipation. During the flow of Newtonian fluids, kinetic energy can be both stored and dissipated, while the flow of viscoelastic soft matter systems, such as polymer fluids, induces the accumulation of both kinetic and elastic energies. The accumulation of elastic energy causes local stiffening of stretched polymer chains, which can destabilise the flow. Migrating multicellular systems are hugely complex and are capable of self-regulating their viscoelasticity and mechanical stress generation, as well as controlling their energy storage and energy dissipation. Since the flow perturbation of viscoelastic systems is caused by the inhomogeneous accumulation of elastic energy, rather than of kinetic energy, turbulence can occur at low Reynolds numbers.This theoretical review is focused on clarifying the role of viscoelasticity in the appearance of low-Reynolds turbulence. Three types of system are considered and compared: (1) high-Reynolds turbulent flow of Newtonian fluids, (2) low and moderate-Reynolds flow of polymer solutions, and (3) migration of epithelial collectives, discussed in terms of two model systems. The models considered involve the fusion of two epithelial aggregates, and the free expansion of epithelial monolayers on a substrate matrix.
软物质流动过程中动态平衡的扰动所引起的惯性效应构成了湍流的一个标志。这种扰动归因于能量存储和能量耗散之间的不平衡。在牛顿流体流动过程中，动能既可以被存储也可以被耗散，而粘弹性软物质系统（如聚合物流体）的流动会导致动能和弹性能的积累。弹性能的积累会导致拉伸的聚合物链局部变硬，这可能会使流动不稳定。迁移的多细胞系统极其复杂，能够自我调节其粘弹性和机械应力的产生，以及控制其能量存储和能量耗散。由于粘弹性系统的流动扰动是由弹性能量的不均匀积累而非动能引起的，所以在低雷诺数下也可能出现湍流。这篇理论综述的重点是阐明粘弹性在低雷诺数湍流出现过程中的作用。我们考虑并比较了三种类型的系统：（1）牛顿流体的高雷诺数湍流流动，（2）聚合物溶液的低雷诺数和中等雷诺数流动，以及（3）上皮细胞聚集体的迁移，这是根据两个模型系统进行讨论的。所考虑的模型包括两个上皮聚集体的融合，以及上皮单层在基质上的自由扩展。
