Simulating multiphase flows using an unstructured moving mesh interface tracking method.

摘要

An interface tracking method using an unstructured moving mesh has been developed for simulating three-dimensional incompressible and immiscible two-phase flow. 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 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 evaluated 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 a number of cases, which include a two-layer Couette flow, an oscillating droplet in a gaseous flow, 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 due to surface tension is simulated in order to show the capability of the method to successfully deal with large deformation. A droplet accelerated by a gaseous flow is computed to investigate the drag coefficient and deformation factor. A modulated jet pinching is simulated to show the robustness of the mesh separation scheme for two-phase flows.