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The thixotropic behaviour of dense cohesive sediment suspensions
Toorman, E.A. (1995). The thixotropic behaviour of dense cohesive sediment suspensions. Katholieke Universiteit Leuven (KUL): Heverlee. iii, 69 pp.

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Keywords
    Cohesive sediments; Mathematical models; Thixotropy

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  • Toorman, E.A., more

Abstract
    Because of changes in the flocculated structure in cohesive sediment (e.g. clay) suspensions, the rheological properties are a function of time. The dependence can be characterized by a structural parameter, which for a certain shear rate only varies with time.
    A theoretical framework has been constructed based on the structural kinetics theory. The Moore model has been investigated in depth. The proposed five parameter model allows the constant structure curves to be constructed with the data of the equilibrium flow curve alone. A model calibration procedure is proposed. The model has been extended to include the often observed static yield stress, which may be attributed to a secondary structure. The model has been validated using two constant structure data sets and two transient behaviour data sets found in the literature. The capability of the model to reproduce these data satisfactorily is very encouraging. The model well predicts hysteresis behaviour. The model has been implemented into a numerical model for the simulation of the flow in the gap of a concentric cylinder viscometer. The results provide better insight into the interpretation of rotational viscometer data. The relevance of many published viscometric data is again questioned in the light of the likely occurrence of a wall depletion layer which causes slip.

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