## 4 Flow Pattern Recognition Results and Discussion  
### Data Processing  
The high-speed camera's video recording of the flow pattern reveals that the primary types of flow include stratified flow, slug flow, annular flow, and bubbly flow. Due to the insufficient memory of the high-speed camera system, ECT tomography equipment was used to record and present the flow pattern transformation process. In the M-type jumper, Figure 13 depicts the distribution characteristics of the four gas-liquid two-phase flow patterns. A distinct gas-liquid phase partition interface, also known as stratified flow, can be seen between the gas and liquid phases in Figure 13a when the apparent flow velocities of the liquid and gas phases are preserved at the same value of 1 m/s. The apparent gas velocity remained unchanged, and the apparent liquid velocity gradually increased. During this period, the liquid level gradually increased, but it was still stratified flow, shown by the changes from 1 to 2 in Figure 14. However, it is different from the straight pipe. Under the influence of the complex structure of the subsea jumper and many elbows, there will be a part of the reflux flow pattern, and the stratification cannot be maintained all the time. As the apparent velocity of the liquid increases, a liquid plug filling the entire flow area of the pipe appears, as shown in Figure 14(3). As the apparent liquid velocity eventually reaches 4 m/s, the airflow pushes the liquid wave to the top of the pipe, blocking the entire flow area and causing a blockage. At the same time, because there is a bend across the subsea jumper, liquid flow to the bend forms a flow around, affecting the flow pattern of the monitoring point. Figure 13b depicts the slug flow in place of the stratified flow at this point. The primary characteristic of the gas phase--which takes the shape of a gas elastic in the tube and travels uniformly along the main flow direction with the liquid phase--is its adherence to the top section. By adjusting the apparent liquid flow rate to 1.6 m/s and the apparent gas flow rate to 2.5 m/s, the flow was stabilized. A layer of the liquid film was discovered to be present along the pipe wall. The majority of the liquid goes forward along the pipe wall as film, as shown in Figure 13c, while the gas rapidly entrains the center of the pipe wall and passes through the pipe as foam. At that point, the flow is annular flow. Different from bubble flow and slug flow, annular flow is less affected by the structure of the subsea jumper, and the flow pattern remains unchanged basically. The next step is to change the flow of gas and liquid at the entrance into a bubble flow. Gradually reducing the liquid flow and gas flow, we can see from the viewable window that there are some obvious bubbles in the mixture, as the gas phase diffuses into the liquid phase as distributed tiny bubbles. This was discovered by diminishing the apparent gas-liquid flow. Almost allthe tiny bubbles are attached to the upper wall surface of the channel. Since the mixture's average flow rate is low and the bubbles' rising speed exceeds the liquid flow rate, this flow type is referred to as a bubbly flow, as seen in Figure 13d. From the flow pattern changes of 6 to 10 in Figure 14, it can be seen that the foam in the annular flow is ensnared in the high-speed water flow and appears green in the ECT image. The bubbles in the bubbly flow are larger and more pronounced, and appear blue in the ECT image. After the steady development of the flow pattern, the ECT tomography system was used to collect about 125 s flow pattern pictures, the frame number was set at 8 fps, and about 1000 flow pattern pictures were collected. The ECT images acquired by capacitance tomography were screened in the ITS Toolsuite equipped with the system, and 650 photos with obvious features, clear images, and less noise were selected from the 1000 data acquired  
Figure 14: ECT image of flow pattern change. Figure 13: Observation of flow patterns with a high-speed camera. for each flow type.