A moving mesh interface tracking method for 3D incompressible two-phase flows

An interface tracking method using an unstructured moving mesh has been developed for simulating three-dimensional, incompressible, and immiscible two-phase flows. The interface mesh is moved in a Lagrangian fashion. A local mesh adaptation method is used to capture the changing interface curvature, maintain good mesh quality, and deal with large deformation. The interface is of zero thickness, so the jump and continuity conditions across the interface are implemented directly, without any smoothing of the properties of the two fluids. This is theoretically beneficial compared to other methods that allow the fluids' properties to continuously vary in an interface region. The curvature for interfacial tension calculation is geometrically computed by a least squares parabola fitting method. A mesh separation scheme for interfacial flows is employed to handle topological transition. The numerical technique is tested and validated by several cases, which include a two-layer Couette flow, an oscillating droplet surrounded by gas, and a droplet in shear flow. The results obtained from numerical simulations are found to be in excellent agreement with analytical solutions and experimental results. A collapsing ligament in a quiescent gas flow and a modulated jet pinching are simulated to show the robustness of the method.