Measurements of unconfined fresh concrete flow on a slope using spatial filtering velocimetry

Numerical Modelling of Multiphase Flow With Application to Industrial Processes

10.23889/suthesis.58693 ◽

2021 ◽

Author(s):

◽

Ashutosh Bhokare

Keyword(s):

Numerical Modelling ◽

Multiphase Flow ◽

Multiphase Flows ◽

Oil And Gas ◽

Fresh Concrete ◽

Industrial Applications ◽

Fluidised Bed ◽

Bingham Model ◽

Drag Models ◽

Concrete Flow

Multiphase ﬂows are witnessed often in nature and the industry. Simulating the behaviour of multiphase ﬂows is of importance to scientists and engineers for better prediction of phenomena and design of products. This thesis aims to develop a multiphase ﬂow framework which can be applied to industrial applications such as placement of concrete in construction and proppant transport in oil and gas. Techniques available in literature to model multiphase ﬂows are systematically introduced and each of their merits and demerits are analysed. Their suitability for diﬀerent applications and scenarios are established. The challenges surrounding the placement of fresh concrete in formwork is investigated. Construction defects, the physics behind these defects and existing tests used to monitor fresh concrete quality are evaluated. Methods used to simulate fresh concrete ﬂow as an alternative to experiments are critically analysed. The potential beneﬁts of using numerical modelling and the shortcoming of the existing approaches are established. It is found that the homogeneous Bingham model is currently the most widely used technique to model fresh concrete ﬂow. Determining the Bingham parameters for a given concrete mix remains a challenge and a novel method to obtain values for them is demonstrated in this work. The Bingham model is also applied to a full-scale tremie concrete placement procedure in a pile. Knowledge on the ﬂow pattern followed by concrete being placed using a tremie is extracted. This is used to answer questions which the industry currently demands. The need for a more sophisticated model is emphasised in order to obtain an even greater understanding of fresh concrete ﬂow behaviour. A CFD-DEM framework in which the multiphase nature of concrete is captured is developed. To validate this framework a new benchmark test is proposed in conjunction with the ﬂuidised bed experiment. A comparative study of the drag models used in CFD-DEM approaches is performed to systematically assess each of their performances. CFD-DEM modelling is then applied to model fresh concrete ﬂow and its potential to model defect causing phenomena is demonstrated. A model to capture more complex behaviours of concrete such as thixotropy is introduced and demonstrated.

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