Spatio-temporal features of oil-air interface for stratified-wavy two phase flow in horizontal pipes with a 6-inch diameter

Interfacial wave characteristics have been studied experimentally in stratified-wavy configuration for oil-air two-phase flow at Tulsa University Fluid Flow Projects (TUFFP) 6-inch low pressure flow loop. Flow rates of each test fluid are adjusted such that the superficial liquid and gas velocities vary between 0.01m/s ≤ υSL ≤ 0.02m/s and 10m/s ≤ υSG ≤ 16m/s, respectively, in horizontal pipe configuration.
During the course of the investigation, the cross-sectional distributions of void fraction are synchronously obtained at two different streamwise locations of the pipe by using two wire mesh sensors, each with a 32 x 32 grid resolution. The spatial distribution of the phases, obtained by analyzing the measured void fractions, reveal several instantaneous quantities of the flow configuration at each cross-section such as interface geometry, liquid holdup, wetted pipe area and liquid height. The sequential acquisition of the void fractions reveal the temporal evolution of these quantities within the planes of measurement. In addition, the cross-correlation of the data from both of the wire mesh sensors enable the characterization of important surface wave parameters such as wave celerity, and structural frequency.
The instantaneous information on the liquid holdup, wetted pipe area and liquid height are the advantages of the current experimental technique over conventional methods employing quick closing valves, and high-speed flow visualization. In order to understand the effect of sensor grid resolution on these quantities, the results have also been re-arranged using coarser mesh configurations by analyzing the same data also on 24 x 24, and 16 x 16 grid sizes. Furthermore, the analysis on the grid size is enriched by the comparison with the results obtained by using other methods for similar flow conditions in other experiments.
The wave celerity is observed to increase with superficial liquid and gas velocities, which is in good agreement with the previous studies. Spectral analyses performed on each element of the data matrix reveal the distribution of the dominant wave numbers within the pipe cross-section. In addition, a unique void fraction reconstruction technique is employed to quantitatively visualize the phase distributions passing through the wire mesh sensor in a three-dimensional fashion. This type of visualization is shown to be effective on the identification of the important wave structures and their spatial distributions within the pipe cross-section. This is a strong advantage over the window crossing method, due to the accuracy in spectral analysis, and over the capacitance sensors due to the global cross-sectional information.