Volume of Fluid

Modeling Multi-Phase Flows

Multi-phase flows are common in many important engineering problems, from internal nozzle flow in a gasoline injector to liquid sloshing in a tank, from dip-lubricated gearboxes to jets in a crossflow.

However, numerically modeling multi-phase flows can be challenging because of the large density difference between phases. Additionally, resolving a sharp interface, especially over a long period of time, can incur a prohibitively high computational cost. CONVERGE’s volume of fluid (VOF) method is an Eulerian-Eulerian approach for modeling multi-phase flows that is capable of accurately capturing the interface. Combined with autonomous meshing, the VOF method efficiently simulates multi-phase flows, even in complex geometries with moving boundaries.

Adaptive Mesh Refinement: Void Fraction

In CONVERGE, you don’t have to trade speed for accuracy. You can accelerate your simulation by coupling CONVERGE’s VOF method with Adaptive Mesh Refinement (AMR) to automatically increase grid resolution at the fluid-fluid interface based on the local void fraction. AMR reduces numerical diffusion and helps you resolve the interface at a reasonable computational cost, even over a long period of time, by adding cells only when and where you need them.

Interface Capturing Schemes

Sometimes it is essential to obtain a sharp resolution of the fluid-fluid interface in your multi-phase simulations. CONVERGE offers two powerful options for interface reconstruction. The High-Resolution Interface Capturing (HRIC) scheme maintains a balance between accuracy and stability and can be used with both compressible and incompressible fluids. For incompressible flows, the Piecewise-Linear Interface Calculation (PLIC) can maintain a sharper interface than HRIC and can accurately resolve topological changes. 

VOF-Spray One-Way Coupling

The VOF method is ideal for detailed multi-phase modeling of internal flow in injectors, but resolving the ensuing spray breakup phenomena using the Eulerian-Eulerian model is computationally expensive. VOF-spray one-way coupling in CONVERGE allows you to simulate the internal and near-nozzle regions of the injectors with the VOF method, then initialize an Eulerian-Lagrangian spray model using the VOF data. The VOF model captures differences between nozzles due to surface effects and needle motion, and the Lagrangian parcel simulation incorporates spray breakup, collision, drag, and evaporation in a model that runs more efficiently.