Eulerian Multiphase 🌶️

Eulerian Multiphase 🌶️

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Eulerian Multiphase

As for the simulation of multiphase flow without using multiphysics, I know that the FEM codes ABAQUS and SHELLS are using such a phase field based modelling approach to do multiphase CFD simulations. I don’t know any a multiphase CFD solver that does not use these approaches.

If I understand your description correctly, the phase field model you describe is basically a derivative of the physical based multiphase phase field function. So it is the same approach as the physical based multiphase phase field function. Therefore, I think that it is also within the domain of Multiphysics. How do you feel about this statement? I think that this will change how Multiphysics is used in the future.

I created the M-S model (MS stands for Multiphysics) to make it possible to use the Multiphysics interface to create multiphase simulations. If you use M-S simulation in COMSOL Multiphysics, than the physics interface of COMSOL should respect your mathematical model. For Multiphysics version 6, it is now possible to write your own multiphase force model instead of using the default physics implementation.

Now you make it clear what is meant with Multiphysics. So it is possible to use the Multiphysics interface and in addition to the multiphase solvers and the multiphase force model, you can use the multiphase physics interface as well. Because the physics interface is a kind of an Application Program Interface (API), it is possible to use it for all Multiphysics objects. This is useful if you need the multiphase interface for a new concept that you are studying for a thesis, but you don’t have time to write the specific physics interface for the new concept yourself. In the FEM user guide you can find a section that explains that it is possible to use the multiphase interface to define multiphase physical quantities.

A major application of multiphase flow modeling is the simulation of mixing, which can include the study of diverse multiphase flow, for instance, dispersed-bubble fluids, dispersed-droplet fluids, and dispersed-solid-particle fluids. A typical multiphase flow system consists of a mixture of many components such as gases, liquids, and solid particles that can be modeled in different forms. The multiphase flow systems can be divided into three main categories: non-mixed systems, simple systems with only two phases, and complex systems with many phases. The non-mixed multiphase flow systems are typically used to simulate systems with two or three phases of simple constituents; examples of these systems include oil-water systems and gas-liquid systems.
Fluid systems with two or more than two phases require the coupling of flow and interface models, often via the level set method. Multiphase systems in which the interface is between two or more phases become more involved and computationally demanding, and include such types of systems as droplet-bubbble, emulsion-bubble, foam, or foam-bubble. Solid particles are often used in multiphase flow systems; examples include multiphase flows and granular systems. Multiphase flow systems composed of solid particles are typically encountered in petroleum engineering, for example, the study of oil-water mixtures with sand emulsions or sand streams in an open channel, and multiphase flow systems with heterogeneous mixtures of solid particles. Multiphase flow systems composed of a continuous phase and a dispersed phase with solid particles or bubbles are also encountered in multiphase systems. Examples of these flow systems include dispersed bubble fluids, dispersed droplet fluids, and dispersed granular fluids. The term Eulerian refers to the fact that the configuration is defined in space, while Lagrangian refers to the fact that the flow of particles or fluid is defined in space. The level set methods provide a non-linear, discontinuous interface between the two phases of a fluid system, which is more accurate than the used in the non-multiphase Eulerian method. The level set method is typically used for such flow system categories as dispersed-bubble fluids, emulsion-bubble systems, and thin film and foam. Multiple methods are available for achieving accurate and efficient Eulerian fluid domain discretizations. The physical methods for Eulerian fluid flow can be broadly divided into two categories: methods that use only the velocities of the fluids and other methods that use both the velocities of the fluids and the stresses on the particles. In the former category, the methods are of two types: point-based methods and volume-of-fluid methods, while the latter category includes fictitious domain methods, finite-volume methods, meshless methods, meshfree methods, and methods using the phase-field method. A class of domain-based methods can be used to generate particle-laden flows on Eulerian grids; examples include particle-laden fluid methods, geometric methods, and adaptive mesh refinement methods.

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