触变流体常见于日常生活中，如：油漆、粘土、血液和原油等。触变流体表现出受外界流动时间历程影响的流变性质。由于存在内部微观结构，在外界流场作用下触变流体微观结构发生演变，产生复杂的流变现象，典型的触变现象包括应力过冲、应力迟滞环、屈服应力等。对于触变流体的研究目前主要包括宏观本构模型和微观结构演变两方面，两方面研究相对独立，相关性研究较少。本项目拟基于耗散粒子动力学方法，构建触变流体微观结构，对其流变微元进行模拟，考察微观结构演变规律，对触变流体本构模型的结构参数动力学方程和本构方程进行修正，提出基于微观结构演变规律的宏观本构模型。通过流变仪实验，验证修正的本构模型对应力过冲、迟滞环和屈服应力等现象的精确模拟。本项目拟进一步研究片状颗粒悬浮液的触变特性及微观结构演变，掌握颗粒形状和柔性等因素的影响规律，推广本构模型，最终为粘土、氧化石墨烯悬浮液等触变流体的工业应用提供理论支撑。

Thixotropic fluid is common in our daily life, such as paint, clay, blood, crude oil, etc. The rheological behavior of thixotropic fluid is influenced by the flow history. Due to evolution of microstructure under the imposed flow field, the rheological behavior of thixotropic fluid is quite complex, and typical phenomena include stress overshoot, stress hysteresis loop and yield stress. Current researches of thixotropic fluid can be divided into two aspects, i.e., bulk constitutive model and evolution of microstructure. While researches of these two aspects are quite independent on each other, and there are few studies on the correlation of these two aspects. In this project, the microstructure of thixotropic fluid is constructed and the rheological cell is simulated by using dissipative particle dynamics method. By investigating the microstructure evolution of the rheological cell, the bulk constitutive model, including the kinetic equation of structure parameter and constitutive equation, is improved. This new constitutive model is validated with experiment of rheometer in the prediction of stress overshoot, hysteresis loop and yield stress. In this project, the suspension with plate shape colloids is further studied and the effects of particle shape and flexibility are investigated. The bulk constitutive model is extended to predict the thixotropic behavior of suspension with plate shape colloidal. The output of this project will provide theoretical support for the engineering application of thixotropic fluid, such as clay, graphene oxide, etc.