Unsteady parallel flows of an elasto-visco-hypoplastic fluid with oscillating boundary

In the present study, an evolution equation for the Cauchy stress tensor is proposed to take elastic, viscous and plastic characteristics of complex fluids simultaneously into account. In particular, hypoplasticity is incorporated to account for the plastic features. The stress model is applied to investigate time-dependent flows of an elasto-visco-plastic fluid driven by an oscillating boundary with/ without an additional stationary boundary to study the cyclic responses and the model performance. Numerical simulations show that while different degrees of elastic and viscous effects can be captured by varying the model parameters, plastic deformation plays a significant role in the velocity distribution, and can be simulated appropriately by use of hypoplasticity. The stress model is capable of accounting for the combined elastic, viscous and plastic features of complex materials in transient motions, and applications may be found in geomorphic fluid motions like granular and debris flows, and flows involving polymers.