Numerical simulations are a powerful tool for resolving non-measurable variables, for making predictions about the material behaviour of complex materials or for running complex large-scale flow processes purely virtually. In order to be able to use these advantages in the context of modern building materials, the numerics Working Group of SPP 2005 is working on the development, implementation and validation of state-of-the-art numerical methods. The range of methods used extends from particle-based methods to continuum models and complex coupled approaches, with the spectrum of flow processes considered ranging from simple shear flows to complex pumping processes.
The goal of the Working Group is to extend existing numerical methods and develop new numerical approaches for describing complex non-Newtonian suspensions such as concrete. These models are intended to generate knowledge that cannot be obtained by experimental methods and to predict the behaviour of fresh concrete in different flow situations. Some key points are summarised here:
Haustein, M. A., Zhang, G., Schwarze, R., Segregation of granular materials in a pulsating pumping regime, Granular Matter, 2019
Secrieru, E., Mohamed, W., Fataei, S., Mechtcherine, V., Assessment and prediction of concrete flow and pumping pressure in pipeline, Cement and Concrete Composites, 2020
12 September 2019
22 October 2019
23 October 2019
02 July 2020
03 August 2020
Benchmark straight Pipe Flow
The Working Group has collaborated on a comprehensive benchmark to compare different simulation methods for modelling suspensions. The associated article “Benchmark Simulations of Dense Suspensions Flow Using Computational Fluid Dynamics” has been published in the journal “Frontiers in Materials” and compares the numerical methods Finite Volume Method (FVM), Finite Element Method (FEM) and Smoothed Particle Hydrodynamics (SPH). Complex material models, as they are necessary for a physical description of the flow behaviour of fresh concrete, often exhibit discontinuities that require special numerical treatment. The Bingham model used in the benchmark is characterised by a yield stress that leads to an unsheared plug in the centre of the pipe. The transition between the sheared and unsheared regions must be treated numerically separately, e.g. using the bi-viscous or Papanastasiou model as done in the benchmark.
Comparison of the velocity-profiles for the different software packages with the constant velocity boundary condition. The regularization with the bi-viscous model is shown on the left side, and the Bingham-Papanastasiou model is shown on the right. The plugflow region is also shown enlarged for u = 0.39 − 0.41 m/s.
CFD-Benchmark: Comparison of different software packages for a velocity profile of a non-Newtonian fluid after a pipe-bend.
DEM-Benchmark: Development of integrated potential and kinetic energy of all particles in a slump flow.
Benchmark Curved Flow
Following on from the first funding period, work is being done on a joint benchmark. The focus of the current work is the consideration of a curved pipe flow, as often occurs in practice when conveying concrete. Different numerical methods and implementations are to be investigated and compared with real measurements on a laboratory scale. An extension of the single-phase approaches from the first funding period to two-phase models taking into account separate liquid and solid phases is being aimed at. The intention of this work is to provide a comprehensive overview of possible methods and their quality for modelling flow processes with building material suspensions.
A numerical discipline that promises great potential in the modelling of fresh concrete is the coupling of particle and fluid simulations. The individual solid particles and their movement within the fluid phase are resolved and the mutual influence of both phases is taken into account. The numerics group of the SPP 2005 is working on the implementation and experimental validation of such modern coupled methods.
Frontiers in Materials 144 (2022)