Claudia Pfeiler

Importance of Melt Flow in Solidifying Mushy Zone

A mixture solidification model is employed to study the interaction between the melt flow and the growing mushy zone. The goal is to address the importance of considering the melt flow and flow pattern (laminar or turbulent) in the growing mushy zone. A simple 2D benchmark with parallel flow passing by/through a vertically growing mushy zone is considered. Parameter studies with different velocities and flow patterns are performed. It is found that the flow velocity and flow pattern in and near the mushy zone plays an extremely important role in the formation of the mushy zone. The mushy zone thickness is dramatically reduced with the increasing melt velocity. Simulations with/without considering turbulence show significantly different results. The turbulence in the mushy zone is currently modeled with a simple assumption that the turbulence kinetic energy is linearly reduced with the mush permeability.

Application of Different Turbulence Models to Study the Effect of Local Anisotropy for a Non-Premixed Piloted Methane Flame

Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications, especially for the steel and refractory industry. Accurate turbulent flow and temperature fields are of major importance in order to predict details on the concentration fields. The performances of the realizable k-ɛ and the RSM turbulence model are compared. Detailed chemistry is included with the GRI-Mech 3.0 mechanism in combination with the laminar flamelet combustion model. The combustion system selected for this comparison is a piloted non-premixed methane flame surrounded by co-flowing air. The simulation results are compared with experimental data of the “Sandia Flame D” published by the international TNF workshops on turbulent flames. For simplification a lot of steady-state flame simulations are performed axisymmetrical in 2D. Simple RANS models do not account for the local anisotropy in turbulent flows. To consider this effect a 3D calculation and the application of the RSM turbulence model, which accounts for these anisotropy, is necessary. In axially symmetric 2D flame simulation the realizable k-ɛ and in 3D the RSM give unexpected similar results. But still the predicted turbulence and temperature field shows some differences to the experimental data. A modification of a single empirical model constant for the turbulence helped to get better results in both, 2D and 3D.

Experimental and numerical modelling of the flow field in a CuxSny direct chill caster

Abstract To investigate the influence of the casting speed on the flow field and the shape of the solidification front in an industrial bronze caster, numerical calculations have been performed and experimental flow field measurements were used to validate the numerical model. Both numerical and experimental model represented 1:1 the real caster geometry of 820 × 250 × 800 mm3. A steady-state calculation, considering solidification and turbulent flow, was performed. Furthermore, a 1:1 water model of the industrial bronze caster has been built and combined with a Particle Image Velocity (PIV) setup to measure the apparent flow fields. Amongst other parameters, the numerical model provided information on the influence of the casting speed on the solidification front shape. The water model gave the experimentalist the facility to adjust the shape of the solidification front to the one predicted by the numerical model and compare the resulting flow field with the numerical prediction. This work presents a comparison of the results of both numerical and experimental models for different casting speeds with the same numerical parameters and boundary conditions.