# Asymmetric Magnetohydrodynamic Propulsion for Oil-Water Core Annular Flow Through Elbow
## 4 Discussion
### Regulatory Factors  
Under the above parameter setting, the oil-water ring can stably pass through the bent pipe section. Through a series of the specific analysis results above, this design of a differential MHD thick oil flow stabilizing gas pedal is able to achieve the stable transport of the elbow oil-water ring. To better combine the practical applications and investigate the effects of regulatory factors in the device, which include voltage, current, conductivity, and gravitational direction, on the development of the oil-water interface, this article will use the control variable method to conduct relevant research. Current, voltage, and conductivity are explored according to the control mode of the device. At the present stage, the industrial voltage in the world is mostly 200 V or 380 V. When studying voltage and current effects on the development of the oil-water interface, the main focus is to explore the stable current ranges of the oil-water ring stabilizing through the elbow pipe under both 220 V and 380 V voltages. First and foremost, maintaining the electrode plate voltage in the accelerator at 220 V, the conductivity of the water phase electrolyte solution at 5 m\(\cdot\)s\({}^{-1}\), and keeping other setup parameters unchanged, the coil current in the device is set to 4 A, 6 A, 8 A, 10 A, 12 A, 14 A, 16 A, and 18 A in that order. The stable shape of the oil-water annular flow in each case and the change rule of the fluid flow rate with the current at the selected position (at the center of the elbow) are obtained through simulation. Here, the longitudinal section of the oil-water volume fraction under the set current parameters of 4-18 A is shown in Figure 6a. The velocity curve drawn from the data recorded by the velocity probe and the correlated pipe cross-section is shown in Figure 6b. Combined with Figure 6a,b, the current range of 4-18 A is divided into three intervals: below 6 A, 6 A-14 A, and above 14 A. When the coil current is less than 6 A, in the case of 4 A, the oil-water rings cannot pass through the elbows properly, and a rupture is produced at the elbow and the outlet. The reason for the rupture phenomenon is that the Lorentz force provided by the electromagnetic device is insufficient to keep the oil-water ring stable past the elbow section, resulting in the rupture phenomenon of the oil-water stratification. Simultaneously, the breaks of the oil-water ring result in the mixing of oil and water in the pipeline, thereby decreasing the speed as observed at the probe monitoring point. Under 220 V voltage, the oil-water ring can pass through the elbow stably in the current range of 6 A-14 A (take the current of 10 A as an example) without the rupture phenomenon, and the oil-water rings at the cross-section show a clear toroidal shape. In this range of current parameters, the magnitude of the velocity recorded at the probe shows a trend of increasing with current. After the coil current is higher than 14 A, taking 16 A and 18 A as an example, the oil-water ring can pass through the elbow stably. However, the fluctuation at the entrance of the pipeline and the rupture after passing through the elbow indicate that the excessive current harms the maintenance of the oil-water ring shape. The reason for the rupture of the oil-water ring caused by the excessive current is that the Lorentz force provided by the electromagnetic device is oversized, which makes the oil-water ring form a vortex at the elbow and makes the center of the oil-water ring shift downward, the oil phase coming into contact with the wall of the lower pipe, destroying the form of the oil-water ring. The velocity recorded by the probe also decreased with the rupture of the oil-water ring. Subsequently, the voltage of the electrode plate in the device is adjusted to 380 V, and the coil current is set sequentially according to the 220 V simulation (the conductivity of the water phase electrolyte solution remains at 5 m\(\cdot\)s\({}^{-1}\), and the other parameter settings are kept unchanged).