## 4 Results and Discussion  
The arrangement of pipeline pressure measuring points in the experiment is shown in Figure 6. The slug flow state in the pipe can be obtained by establishing the pressure model of the slug flow at the above four moments. The pressure of point A and \(p_{1}\), \(p_{2}\), \(p_{3}\), and \(p_{4}\) in the slug flow pressure model established in Section 3 can be measured in the experiment. Therefore, the pressure difference between point A and \(p_{1}\), \(p_{2}\), \(p_{3}\), and \(p_{4}\) at different times is used as the method of model verification. According to the pressure difference between measuring point A at different times and the measuring point on the inclined pipe, the state of slug flow in the pipe can be judged, which has a guiding significance for identifying the flow in the pipe. To verify the correctness of the slug flow pressure model, the model value is calculated and compared with the measured pressure value. In the experiment, at the gas velocity is 9.89 m/s and an inclination of 5\({}^{\circ}\), slug flow does not occur when the liquid accumulation is 50 mL. However, at the same speed and angle, the slug flow occurs when the liquid accumulation volume is 80 mL, 100 mL, 200 mL, and 300 mL. The experimental and model calculation results of slug flow pressure difference under different liquid accumulation conditions are displayed in Figure 7.  
It can be seen from Figure 7 that the error between the experimental and model calculated values is within \(\pm\)20%. In general, the calculated value of the model is slightly larger than the experimental value. The main reason is that the slug flow completes a periodic movement continuously and rapidly in the experiment, and it is difficult to accurately divide every moment, which leads to the deviation of the measured pressure value. The secondary cause is the error caused by sensor measurement and experimental equipment. The pressure difference in Figure 7 is divided into two stages, falling and rising. The pressure difference from t1 to \(t_{3}\) is decreased, the reason is that the elbow is blocked by liquid accumulation, and the pressure at point A increases sharply due to the gas being compressed. While the pressure of the inclined pipe does not change much because it is connected to the outside, so the pressure difference is large. Figure 6: Pipeline pressure detection distribution. Figure 7: Verification of slug flow pressure model with an inclination of 5\({}^{\circ}\). Figure 8a-d are the slug flow movement images with the liquid accumulation of 300 mL. It can be seen that the liquid accumulation volume at point A decreases gradually from \(t_{1}\) to \(t_{3}\), while the liquid accumulation volume at point \(P_{4}\) increases from \(t_{1}\) to \(t_{2}\), and decreases to the minimum at \(t_{3}\). When the moment is \(t_{3}\), the slug in the pipe is partially discharged, and the gas in the pipe is interlinked at this time, so the pressure difference at \(t_{3}\) is the smallest. With the increase in the pressure difference from \(t_{3}\) to \(t_{4}\), the backflow of the liquid in the pipe makes the liquid accumulation pressure at point A increase again. However, the direction of the liquid backflow in the inclined pipe is opposite to the gas, and the impact of the two fluids causes the pressure to rise, which makes the pressure difference of \(t_{4}\) less than \(t_{1}\). At \(t_{4}\), the liquid accumulation at A accumulates again, and the fluid amount at \(P_{4}\) is also more than \(t_{3}\), as shown in Figure 8d. As the inclination of the pipe increases to \(10^{\circ}\), the error range of the pressure difference between the experiment and the model calculation is also within \(\pm 20\%\). The trend of pressure difference is also divided into two stages, falling first and then rising as shown in Figure 9. The pressure difference of \(10^{\circ}\) has little change compared with that of \(5^{\circ}\).