| The overall objectives of the research program are to develop a data base and predictive numerical methods for describing the bubbly, two-phase flow structure and its transitions through 90° elbow in horizontal configurations. To achieve these objectives, the research program is divided into two major tasks, namely, Numerical Model Development and Experimental Program. The knowledge of the interfacial parameters such as the local void fraction and the interfacial area concentration is quite limited due to considerable difficulties in experimental measurements and complexity of the two-phase flow field in terms of the predictive methods.The internal flow structure development and its transitions of gas-liquid, bubbly two-phase flow in horizontal configurations have been numerically investigated by using an integrated Computational Fluid Dynamics (CFD) method. To simulate this complex phenomenon, customized functions are incorporated into the mixture multi-phase flow model in the FLUENT 6.1 code. For the purpose of verifying and validating the CFD simulations with those of experimental observations, the preliminary CFD predictions compared with those of experimental observations of air-water two-phase flow through 90° elbow in horizontal configurations. The experimental data range was extended at Jf = 3.7, 4.0 and 4.3 m/s with increasing gas superficial velocities to J g = 0.1, 0.25, 0.50, 0.75 and 1.0 m/s. The results were documented in terms of the local and area-averaged void fraction, interfacial area concentration and bubble velocities at a location of 0.48 m upstream and 0.91m, 2.21m, 6.17m downstream of the 90° elbow in 50.3 mm transparenced tubings.In the CFD simulation, 3-D two-phase mixture model was used to analyze the internal flow structure development of the gas-liquid in horizontal configurations. The local and area-averaged void fractions of the both the CFD predictions and experimental observations are directly compared for a 90° elbow flow transitions. The CFD predictions of those interfacial characteristics are encouraging in verifying the experimental local measurements. The experimental measurements validate the phenomenological models and the interfacial transport equations that were incorporated into the code. Considering the complexity of the two-phase flow fields, the predictions are satisfactory as validated by the carefully designed experimental measurements. |
