# Asymmetric Magnetohydrodynamic Propulsion for Oil-Water Core Annular Flow Through Elbow
## 1 Introduction
[14] examined the capability of a VOF model to simulate horizontal oil-water two-phase flow with matched density and a medium viscosity ratio under flow rates corresponding to different flow patterns, namely, core annular flow, oil plugs in water, oil bubbles in water, and dispersed flow. [PERSON] et al. [25] used CFD simulations to find the hydrodynamic conditions under which the flow in the core annulus becomes unstable and the oil wave comes into contact with the pipe wall, and they obtained a series of relevant conclusions. [PERSON] et al. [30] used simulation to develop a quasi-three-dimensional numerical model of the axial pressure gradient, interface height, water content, and flow field in an oil-water two-phase stratified pipe flow, which solves the governing equations of steady axial momentum and mass conservation equations and solves a low-Reynolds-number k-\(\epsilon\) turbulence model of vortex viscosity in a bipolar coordinate system, which facilitates the description of the curved interfaces and the mapping of the physical domain. [PERSON] et al. [32] used the computational fluid dynamic (CFD) method to study and analyze the effects of the inlet water fraction, the oil-water property, and geometric parameters on hydrodynamic performance in the development of core annular flow (CAF), and the results could provide a reference for the design of 90\({}^{\circ}\) elbow structures and the optimization of flow parameters. [PERSON] et al. [33] used numerical simulation to compare the interface fluctuations and energy-saving performance of oil-water annular flow under different pipeline structures, flow parameters, and fluid properties, which provide a reference for the design of heavy oil transportation pipelines, the analysis of interface fluctuation, and the energy-saving evaluation of oil-water annular flow. The CFD simulation was also used by [PERSON] et al. [34] to study the axisymmetric, laminar-laminar oil-water core annular flow in a pipe (radius 14.2 mm) without the gravitational effect under three different channel conditions: vertically upward flow, vertically downward flow, and without considering the gravitational effect. Although the above studies apply numerical simulation methods to study the influence of parameters (such as density, viscosity, and others) in oil-water characteristics on the stability of oil-water annulus flow in pipelines and provide references for the design of pipes and the optimization of oil-water flow parameters in actual production, some limitations still exist. The range requirements of oil-water characteristics, transport parameters, and other related parameters make oil-water annular flow transport have certain restrictions. For elbows where the rupture of the oil-water ring is more serious, the oil-water parameters and design of the elbows need to be set more accurately to ensure the oil-water ring passes through stably, which significantly limits the development and practical application of oil-water annular flow. To ensure the smooth passage of the oil-water ring through the elbow without the restriction of pipe flow parameters, a universal and independent method urgently needs to be developed to stabilize the oil-water ring annular flow in elbows. Here, we present an asymmetrical magnetohydrodynamic (MHD) propulsion method to utilize the significant difference between the conductivity of heavy oil and an electrolyte solution to achieve the accelerating driving effect on the outer water ring. Without changing the design of the pipeline, the device can break through the range requirements of oil-water properties and oil-water ring conveying parameters by changing the voltage, current, or water ring conductivity and achieve the perfect conveying of the oil-water ring.