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In this paper, three different regimes including annular, stratified and homogeneous in the range of 5%-90% void fraction, were simulated by Mont Carlo N-Particle (MCNP) Codes. In simulated structure, a cesium 137 source and two Nal detectors were used to record received photons. In this study, the Fast Fourier Transform (FFT) was applied to the registered signals from two detectors in order to analyze in the frequency domain. Several features of signals in the frequency domain were extracted using average value of fast Fourier transform, the amplitude of dominant frequency, kurtosis, Standard Deviation (STD), RMS (Root Mean Square) and Variance. The same features were extracted from analyzed signals of both detectors in order to find the best separation patterns. These extracted features were used as inputs of artificial neural networks (ANNs) to increase the efficiency of two-phase flowmeters. Two multi-layer perceptrons (MLP) neural networks were implemented in MATLAB software in order to classify flow regimes (annular, stratified and homogeneous) and predict the void fraction. All of the training and testing data were obtained correctly and the mean relative error percentage of the predicted void fraction was 1/15 %.

In this paper, the convection-diffusion process in a two-phase air-water flow is investigated. Two-phase flows of air and water are important and are widely used in the industrial applications. Simulation of such a flow needs a proper understanding of the interface between two phases where there is a change in the fluid properties. Smoothed Particle Hydrodynamics (SPH) is a fully Lagrangian and meshless method which can simply detect the interface of multiphase flows. Here, we develop the open-source SPHyiscs2D code into two phase and implement the convection-diffusion equation by looking carefully at surface tension forces. To validate, first the still-water problem is investigated to ensure that the hydrostatic pressure at the interface is predicted and then the dam-break problem on an infinite bed is compared with the available experimental data. Results show that the combination of surface tension formulations and an additional artificial force gives a better result. Finally, the convection-diffusion process and the concentration distribution are shown for the air-bubble rising problem for different diffusive coefficients. It will be shown that the SPH method is a useful tool for studying multiphase flows and convection-diffusion processes. [ABSTRACT FROM AUTHOR]