Spreading of granular pastes: from the particle to end use properties

颗粒状浆体作为高度浓缩的颗粒悬浮体，如石膏浆体和新拌混凝土，在建筑、化工和食品工业的不同产品的制造中发挥着重要的作用。这些材料是非牛顿流体，其复杂的流变性(屈服应力、触变性)需要用基于物理的模型来理解和描述，以优化这些产品与其配方相关的最终用途特性。优化浆体流动性能的一种可能性是应用机械振动来有针对性地控制其粘度。在这个合作项目中，我们将结合实验和数值工具来研究振动影响下颗粒浆体的流动行为。在微观尺度上，可以得到微观过程的特征参数以及相间相互作用(颗粒-颗粒、颗粒-流体、颗粒-壁面和流体-壁面)。利用离散单元法(DEM)对颗粒进行数值模拟。为了考虑液体和颗粒之间的微观相互作用，DEM将与CFD方法相耦合。这些模型将在粒子过程工程研究所(德国凯泽斯劳滕大学)开发。它们将通过在LEMTA实验室(法国南希洛林大学)进行的流变学实验进行验证。基于实验和数值结果，我们将能够识别剪切流、颗粒输运和能量耗散的机制，为宏观尺度的物理模型提供参数。借助于开发的多尺度模型，可以获得振动过程中微观过程对颗粒浆体宏观流动行为影响的详细信息。这可用于控制配方的粒状浆体铺展性能的优化。

Granular pastes as highly concentrated particle suspensions, such as gypsum pastes and fresh concretes, play an important role in the manufacturing of different products in the construction, chemical and food industries. These materials are non-Newtonian fluids whose complex rheological properties (yield stress, thixotropy) need to be understood and described with physical based models to optimize the end-use properties of these products in connection with their formulation. One possibility to optimize the flow behavior of the pastes is to apply mechanical vibration for targeted control of their viscosity. In this cooperation project, we will combine the experimental and numerical tools to investigate the flow behavior of granular pastes under influence of vibration. On the microscale the characteristic parameters of the micro processes and the interactions between phases (particle-particle, particle-fluid, particle-wall and fluid-wall) will be obtained. The particles will be simulated with the help of the Discrete Element Method (DEM). To consider the micro interactions between the liquid and particles the DEM will be coupled with a CFD approach. These models will be developed at the Institute of Particle Process Engineering (University of Kaiserslautern, Germany). They will be validated with the rheological experiments performed at LEMTA laboratory (University of Lorraine, Nancy, France). Based on the experimental and numerical results we will be able to identify the mechanisms of the shear flow, particle transport and energy dissipation to provide the parameters that can be used in physical models on the macroscale. With the help of a developed multiscale model, it will be possible to obtain detailed information about the influence of the microprocesses on the macroscopic flow behavior of the granular pastes during vibration. This can be used for the optimization of the spreading properties of granular paste with controlled formulation.