The dynamics of model colloidal gels under a steady shear flow is studied by means of a Brownian dynamics (BD) simulation while applying orthogonal superposition rheometry, which superimposes a small amplitude oscillatory flow orthogonal to the main flow direction. Orthogonal dynamic frequency sweep (ODFS) curves are obtained at various magnitudes of the main flow, which shows shear thinning behavior of the colloidal gel. The viscoelastic spectra of the ODFS can be superimposed onto a master curve by the horizontal shift factor, which is equivalent to particle viscosity. That is, the shear rate controls a single master clock for all viscoelastic spectra of the ODFS in the form of a time–shear rate superposition, which bears an analogy with the time–temperature superposition of polymeric systems. In the low-frequency region of the master curve, both orthogonal moduli are well superimposed onto a single master curve, whereas the loss modulus deviates slightly from the master curve in the high-frequency region, which coincides with the experimental findings. We observe spatial and time-varying structural properties in both low- and high-frequency regions on the ODFS curves by decomposing the pair distribution function. It is verified that each flow condition shifted onto the same stress level on the master curve shows identical spatial orthogonal moduli at all radial distances despite the differences in the aggregate size and average particle connectivity.

中文翻译：

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正交叠加流变学的布朗动力学模拟：胶体凝胶的时剪速率叠加

借助布朗动力学（BD）模拟，同时应用正交叠加流变法研究模型胶体凝胶在稳定剪切流下的动力学，该正交叠加流变仪将与主流动方向正交的小振幅振荡流叠加。在各种主流流量下获得正交动态频率扫描（ODFS）曲线，该曲线显示了胶体凝胶的剪切稀化行为。ODFS的粘弹性谱可以通过水平移动因子叠加到主曲线上，该水平移动因子等效于颗粒粘度。也就是说，剪切速率以时间-剪切速率叠加的形式控制ODFS的所有粘弹性谱的单个主时钟，这类似于聚合物系统的时间-温度叠加。在主曲线的低频区域，两个正交模均很好地叠加在一条主曲线上，而损耗模量在高频区域与主曲线略有偏离，这与实验结果相吻合。通过分解对分布函数，我们在ODFS曲线的低频和高频区域都观察到了空间和时变的结构特性。可以验证的是，尽管聚集体尺寸和平均颗粒连通性有所不同，但在主曲线上转移到相同应力水平的每个流动条件在所有径向距离上都显示出相同的空间正交模量。通过分解成对的分布函数，我们在ODFS曲线的低频和高频区域都观察到了空间和时变的结构特性。可以验证的是，尽管聚集体尺寸和平均颗粒连通性有所不同，但在主曲线上转移到相同应力水平的每个流动条件在所有径向距离上都显示出相同的空间正交模量。通过分解成对的分布函数，我们在ODFS曲线的低频和高频区域都观察到了空间和时变的结构特性。可以验证的是，尽管聚集体尺寸和平均颗粒连通性有所不同，但在主曲线上转移到相同应力水平的每个流动条件在所有径向距离上都显示出相同的空间正交模量。