# Detection of Gas-Solid Two-Phase Flow Based on CFD and Capacitance Method
## 1 Introduction
[PERSON] [10] studied numerical simulation of a dense solid particle flow inside a cyclone separator. The two-phase gas-solid particles flow was modeled using a hybrid Euler-Lagrange approach, which accounts for the four-way coupling between phases. Compared to experimental data collected at the in-house experimental rig, the cyclone pressure drops evaluated numerically under-predicted the measured values. [PERSON] [11] studied gas-solid two-phase flow via CFD. Simulations and experimental studies on the relevant phenomena in pipes were carried-out in the study. The pipes' diameters were 26 and 9.5 m, respectively; Volume of Fluid (VoF) multiphase flow model was used in the simulation. Compared to the results in the experiment, a quantitative agreement between calculations and experimental data for the elongated bubble length and the time variation of the liquid hold-up are indicated. Some researchers have also made efforts on the method and model in numerical simulation. [PERSON] [12], in Singapore, studied a new model based on Euler-Lagrange Equations, called Lagrangian algebraic slip mixture model. This model implements the contact between Euler model and the Lagrangian models. This new model was validated by comparing the experiment and simulation in the Two-Fluid model. [PERSON] et al. [13] studied the erosion rate of the horizontal pipe by two-phase flow analyses. They proposed a forecasting model for the pipeline erosion rate based on the discrete stochastic model. The simulation results and experimental data were compared,and particle impact angle and velocity were assessed. The new model can estimate erosion rates more accurately, especially in the gas and small particle flow. There are also lots of studies about the liquid film. [PERSON] [14] studied circumferential liquid film distribution in annular two-phase flow, he used the conductance probe detected thickness distribution in an air-water horizontal annular two-phase flow. He found the thickness of the liquid film was influenced by the superficial liquid velocity. At the higher superficial gas velocity, a more uniform liquid film thickness distribution is commonly found. Moreover, compared to the available experimental data, the correlation has a good capability to predict the circumferential liquid film thickness distribution. [PERSON] [15] studied droplet impact on a flowing liquid film in annular two-phase flow via simulation. A novel control volume finite element method with adaptive unstructured meshes was employed here to study three-dimensional droplet deposition process in the annular two-phase flow. The results in simulation agree with the experimental observations demonstrating the capability of the present method. [PERSON] [16] studied flow structure and flowed regime in large diameter pipes. In his study, adiabatic air-water two-phase flow experiments were been conducted to investigate flow regimes and their transitions. The Probability Density Function (PDF) and Cumulative Probability Density Function (CPDF) of area-averaged void fraction signals were utilised as the indicators for Self-Organised Neural Network (SONN) method to identify horizontal and vertical downward flow regimes, respectively. The results show that the flow regime maps agree well with that of 101.6 mm, but do not agree well with that of smaller diameter pipes (25.4 mm and 50.8 mm). A set of new transition criteria have been developed for downward flow regime transitions in large diameter pipes, which provide more accurate predictions for downward flow regime transitions in large diameter pipes. [PERSON] [17] studied gravitational effects in horizontal annular liquid-gas flow in the simulation. There are three different sets of conditions in the annular and stratified-annular flow regimes in the simulation. A simple model is developed that helps to characterise the dynamics of the liquid annulus and aids in understanding the effect of secondary gas flow on the circumferential motion of the film. [PERSON] et al.