Multiphase flows are ubiquitous both in nature and industry. A broad range of interfacial scales, ranging from fine dispersions to large segregated interfaces, is often observed in such flows. Standard multiphase models rely on either the interface-averaging approach, which is suitable for the modelling of dispersed flows, or on the interface-resolving approach, which is ideal for large segregated interfaces. This results in the inability of such models to deal with complex multiscale flows, and different generalized hybrid modelling approaches having been proposed to overcome this shortcoming. This work presents a novel generalized multifluid modelling approach where large segregated interfaces are identified in the multifluid field from the local interface topology and resolution, avoiding the need for a-priori thresholds of the local volume fraction used in the majority of the models available in the literature. Interface compression and suitable modelling closures for drag and surface tension are activated in the large interfaces regions, whilst the model reverts to a standard multifluid formulation in the regions of small/dispersed interfaces. An assessment against different benchmark cases shows that the approach is as accurate as one-fluid interface-resolving techniques for large/segregated interfaces, while successfully recovering the expected multifluid behaviour for fully dispersed flows. Further, a prototypical multiscale flow has been simulated to demonstrate that the model can effectively switch between large-interface and dispersed-interface mode based on the local flow conditions and mesh size. It is concluded that the present approach represents a promising step towards the development of a comprehensive multiphase model capable of simulating complex multiscale flows of industrial interest.

在自然界和工业界，多相流都是无处不在的。在此类流动中，通常会观察到范围广泛的界面垢，从细分散物到大的隔离界面。标准的多相模型依赖于适用于分散流建模的接口平均方法，或依赖于适用于大型隔离接口的接口解析方法。这导致这种模型无法处理复杂的多尺度流，并且已经提出了不同的广义混合建模方法来克服该缺点。这项工作提出了一种新颖的广义多流体建模方法，该方法从本地接口拓扑和分辨率中在多流体字段中识别出较大的隔离接口，避免了现有文献中大多数模型中使用的局部体积分数的先验阈值。在大的界面区域中激活了界面压缩以及用于阻力和表面张力的合适的建模闭合，而在小/分散界面区域中，模型恢复为标准的多流体配方。针对不同基准案例的评估表明，该方法与用于大型/隔离界面的单流体界面解析技术一样准确，同时可以成功地恢复完全分散的流体的预期多流体行为。此外，已对原型多尺度流进行了仿真，以证明该模型可以根据局部流条件和网格大小有效地在大界面模式和分散界面模式之间切换。