Recent studies have highlighted that oscillatory and time-dependent shear flows might help increase the flowability of dense suspensions. While most focus has been on cross-flows we here study a simple two-dimensional suspensions where we apply simultaneously oscillatory and stationary shear along the same direction. We first show that the dissipative viscosities in this set-up significantly decrease with an increasing shear-rate magnitude of the oscillations and given that the oscillatory strain is small, in a similar fashion as found previously for cross-flow oscillations. As for cross-flow oscillations, the decrease can be attributed to the large decrease in the number of contacts and an altered microstructure as one transitions from a steady shear to an oscillatory shear dominated rheology. As subresults we find both an extension to the $\mu \left(J\right)$ rheology, a constitutive relationship between the shear stresses and the shear rate, valid for oscillatory shear flows and that shear-jamming of frictional particles at oscillatory shear dominated flows occurs at higher packing fractions compared to steady shear dominated flows.

中文翻译：

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致密悬浮液从稳态剪切流变到振荡剪切流变

最近的研究强调振荡和时间相关的剪切流可能有助于增加致密悬浮液的流动性。虽然大多数注意力都集中在横流上，但我们在这里研究了一个简单的二维悬架，在该悬架中，我们沿同一方向同时施加了振动和静态剪切力。我们首先证明耗散在这种情况下，粘度随振荡的剪切速率幅度的增加而显着降低，并且鉴于振荡应变较小，其方式与以前对横流振荡的发现类似。至于横流振荡，这种下降可归因于随着从稳态剪切转变为振荡剪切为主的流变学，接触数量的大幅减少和微观结构的改变。作为子结果，我们发现对$\mu （Ĵ）$ 流变学是剪切应力与剪切速率之间的本构关系，对振荡剪切流有效，并且与稳定剪切占优势的流相比，在振荡剪切占主导的流中摩擦颗粒的剪切堵塞发生在较高的填充率下。