Network science insights into rheology of dense suspensions

What is it about?

Some dense particle suspensions exhibit unusual behavior; they flow like liquids at rest but become thick or even solid when stirred rapidly. This puzzling behavior, known as discontinuous shear thickening, occurs when particles get close enough to form the frictional contact network. Here, we use network science tools to unravel the microscopic underpinnings of this phenomenon. We find that the number of third-order loops, which are the minimally rigid structures, is key to understanding why and how suspensions become more viscous when sheared.

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Photo by engin akyurt on Unsplash

Photo by engin akyurt on Unsplash

Why is it important?

Dense particle suspensions—like concrete, toothpaste, or mud—are common in both industry and nature, yet their flow behavior remains notoriously difficult to predict. A long-standing question that has puzzled engineers and physicists is why these materials suddenly become much more viscous—or even solid—when pushed hard. Our study shows that the answer lies in the structure of the frictional contact network between particles. In particular, we identify the number of third-order loops as the key element. This insight provides a simple yet elegant explanation for a complex phenomenon, potentially guiding the design of materials and processes across various fields, including manufacturing, geophysics, and beyond.

Perspectives