Thixotropy is a reversible time-dependent phenomenon in fluids, in which an internal structure grows due to flocculation and breaks down under shear action. Numerous fluids are thixotropic, e.g. concretes and cementitious suspensions. Pumping of concrete is an important application. Since current approaches omit thixotropic effects, we aim to develop a simple theoretical model to evaluate or understand the significance of thixotropy on the concrete pumping behaviour. We therefore extended Poiseuille flow for thixotropic concretes and reformulated it in a dimensionless form to gain insights. After a validation, the results and significance are elaborated and concluded. Results showed that for increasing thixotropy and decreasing flow rates, the plug radius, wall shear rate and pumping pressure loss increase. Even though all thixotropy mechanisms may not be covered, a simple model is delivered to interpret or predict the effect of thixotropy on the pumping behaviour of cementitious suspensions. The dimensionless formulations via the Bingham number Bn and related discharge diagrams are sufficiently elegant for computational implementation and very insightful to distinguish a thixotropic flow regime. The model could be extended for more complicated thixotropies, irreversible time-dependent effects or even other pumping related phenomena.

中文翻译：

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Poiseuille流动扩展技术对触变混凝土泵送的见解

触变性是流体中一种可逆的时变现象，其内部结构由于絮凝而增长，并在剪切作用下分解。许多流体是触变性的，例如混凝土和水泥悬浮液。泵送混凝土是重要的应用。由于当前的方法忽略了触变效应，因此我们旨在建立一个简单的理论模型来评估或理解触变对混凝土泵送性能的重要性。因此，我们将触变混凝土的泊瓦流扩展为无量纲形式，并对其进行了重新表述，以获取更多见识。验证后，将详细阐述和总结结果和意义。结果表明，随着触变性的增加和流速的降低，旋塞半径，壁面剪切速率和泵压损失增加。即使可能无法涵盖所有​​触变性机理，也可以提供一个简单的模型来解释或预测触变性对水泥质悬浮液泵送行为的影响。通过Bingham数Bn和相关的排放图的无量纲公式对于计算实现而言足够优雅，并且对于区分触变流态非常有见地。该模型可以扩展为更复杂的触变性，不可逆的时变效应甚至其他与抽运相关的现象。通过Bingham数Bn和相关的排放图的无量纲公式对于计算实现而言足够优雅，并且对于区分触变流态非常有见地。该模型可以扩展为更复杂的触变性，不可逆的时变效应甚至其他与抽运相关的现象。通过Bingham数Bn和相关的排放图的无量纲公式对于计算实现而言足够优雅，并且对于区分触变流态非常有见地。该模型可以扩展为更复杂的触变性，不可逆的时变效应甚至其他与抽运相关的现象。