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Slump flow test
Test setup and Geometry
This section presents results of slump flow simulations. It is a typical test usually used in industry to check the consistency of a concrete. The mould called slump cone is filled with concrete and then is lifted up. Conrete slump down and in dependence of type of the concrete, one can measure residual height or spreading diameter. As a geometry, Abrams cone was choosen (see the picture below).
Computational Model
The problem is modeled in axisymmetric setting due to the rotational symmetry of the problem. The scheme of computational domain with description of boundary conditions and used materials is on the next picture. The whole problem is modeled as a two-phase flow problem. Since the fluids (concrete and air) are immiscible, problem can be resolved finding position of the interface between both fluids in each time step. This is done using Level Set Method []. Air is modeled as a newtonian fluid, Bingham model is used for concrete. Parameters were following:
- density 2300 kg/m3,
- yield stress 40 Pa,
- viscosity 20 Pa.s.
The simulations were performed for different type of friction conditions assumed on horizontal plate. The full slip as well as different friction coefficients has been considered. The friction coefficient is sequentially equal to 0.0, 0.01, 0.1 and 5.0. Significant difference in flows for different friction coefficient can be observed.
The mesh is shown on the next picture. It is refined near the botom surface to improve accuracy of the interface capturing. It is solved using linear triangular elements (linear both in velocity and pressure field). Since that element is not satisfying LBB condition, PSPG stabilization is used for preventing oscilations in pressure field. SUPG stabilization improving accuracy in connection with non-linear convective term is also used. For further information, see [1].
Example input file is here: slump_beta0.01_tau40.0_mu20.0_oofem.in
Description of input file can be found here: Input File Description
Results
On the next four videos, the influence of boundary condition on the flow is shown. The friction coefficient is sequentially equal to 0, 0.01, 0.1 and 5. Parameters of the concrete are always yield stress 40 Pa and plastic viscosity 20 Pa.s. Density is 2300kg/m3.
On the next figure, influence of friction is shown. Final spreading shape of SCC is plotted for different values of friction. Comparison with analytical solution of simplified problem is made (for further reference, see: [1]
References
[1] ROUSSEL N COUSSOT P, “Fifty-cent rheometer” for yield stress measurements : from slump to spreading flow, Journal of Rheology, 49(3) (2005) 705-718.)