Numerical Simulations of Two-Phase Flow in a Dorr-Oliver Flotation Cell Model
Abstract: Two-phase (water and air) flow in the forced-air mechanically-stirred Dorr-Oliver machine has been investigated using computational fluid dynamics (CFD). A 6 m 3 model is considered. The flow is modeled by the Euler-Euler approach, and transport equations are solved using software ANSYS-CFX5. Unsteady simulations are conducted in a 180-degree sector with periodic boundary conditions. Air is injected into the rotor at the rate of 2.63 m 3 /min, and a uniform bubble diameter is specified. The effects of bubble diameter on velocity field and air volume fraction are determined by conducting simulations for three diameters of 0.5, 1.0, and 2.0 mm. Air volume fraction contours, velocity profiles, and turbulent kinetic energy profiles in different parts of the machine are presented and discussed. Results have been compared to experimental data, and good agreement is obtained for the mean velocity and turbulent kinetic energy profiles in the rotor-stator gap and in the jet region outside stator blades.
Modelling Velocity Distributions and River
Bed Changes Using Computer Code SSIIM below
Sills Stabilizing the Riverbed
The aim of this study was risk assessment regarding the local scours below sills that stabilize the Warta riverbed below Jeziorsko Reservoir. The studied river sills were constructed due to the reduction of riverbed erosion that took place downstream behind the dam reservoir. The research area embraced two reaches: in the vicinity, sills No. 3 (km 480+902) and No. 4 (km 479+225) were built in order to reduce local and general riverbed erosion resulting from the construction of the reservoir. The current article presents the methodology of the conducted field research and a short description of the applied mathematical model SSIM (a three-dimensional numerical model for simulating sediment movements in water intakes with multiblock options). Based on field geometry measurements of the local scour holes, the distribution of water velocity, and the water levels in the period 20062010, calculations of velocity distributions at the sill have been carried out using SSIIM software. The computer simulations have shown that the calculated water velocity profiles did not differ significantly from the measured ones.
Water model and CFD studies of bubble dispersion and inclusions removal in continuous casting mold of steel
A water model study was undertaken to investigate bubble dispersion and inclusions removal by bubble adhesion in continuous casting mold. The water flow rate was varied in the range of 37-74 L/min, which is equivalent to 1.0-2.0 m/min of the casting speed in continuous casting process. The gas flow rate was varied in the range of 0-2.5 L/min. Silver coated hollow glass beads (SCHG) and plastic particles were used to imitate the inclusions and to investigate the effect of wettability, i.e., contact angle of the inclusions with liquid, on inclusion removal by bubble adhesion. Effect of gas and water flow rates on bubble dispersion in the mold was systematically determined. Inclusion removal at different gas and water flow rates was quantitatively determined. It was identified that the wettability of inclusions with liquid was a decisive factor in inclusion removal: with low wettability, i.e., high contact angle, removal efficiency increased with increasing gas and liquid flow rates, whereas removal efficiency was hardly affected by gas flow rate with high wettability, i.e., low contact angle. To interpret the results of the water model experiments, various computational fluid dynamics (CFD) models which had been reported were applied. None of them was able to represent the experimental results within an acceptable discrepancy. Two new CFD models, which employed a modified Reynolds number and force field theory around the bubble, were developed to simulate bubble dispersion and inclusion removal, respectively. The results indicated that these models could simulate bubbles dispersion and inclusion removal and showed reasonable agreement with results of water model in continuous casting mold.