Dear Kareemulla, The study of multiphase flows with mathematical modeling may be done at several scales. The classic domains of structural analysis, heat transfer, fluid flow, mass transport, and electromagnetic potential are typical issue areas of interest. For non-Newtonian fluids, you can use the generic yet predefined rheology models for viscosity, such as Power Law, Carreau, Bingham, HerschelBulkley or Casson for easy model setup. It is difficult yo help you with this specific model without seeing the actual model. Stay tuned as we continue our discussion of multiphase flow simulation on the blog! I had to dig quite deeper into the literature to figure out the tuning of such parameters and I have found out that simulation results are highly dependent on these parameters especially for cases where the motion of contact lines is simulated. A questions I had: How to choose the best mesh deformation constraint? Colloidal suspensions may exhibit shear thickening behavior, where viscosity increases substantially with shear rate. Pipes and channels connected to 2D/3D fluid domains with nonisothermal flows, for both laminar and turbulent flows. In a Pipe I have 2 inlets and 1 outlet. They are therefore preferred when there is a relatively small number of particles of a dispersed phase in a continuous fluid. The main objective of FSI analysis is the computation of stress and strain in the structure as well as the velocity and pressure field of the fluid flow. (COMSOL) simulation and the experimental one for a single phase on smooth and All of these pairs are listed in the Pair Selection section of the Fluid-Structure Interaction, Pair feature. These scales can span about eight orders of magnitude, where the largest length scale may be a hundred million times larger than the smallest scales. Two-phase flow with water and air in a reactor modeled using the level set method in combination with the k-e turbulence model. The configuration is shown in Figure 2. We will surely take this into account for the next release. COMSOL 6.1 ; COMSOL 6.0 . There are three different interface tracking methods in the COMSOL Multiphysics software for separated multiphase flow models: Level set Phase field Moving mesh The level set and phase field methods are both field-based methods in which the interface between phases is represented as an isosurface of the level set or phase field functions. The isosurface of the phase field function represents the free surface. Multicomponent transport and reactions in diluted and concentrated mixtures, using the mixture-averaged model or Fick's law. When we have a few (tens of thousands but not billions) very small bubbles, droplets, or particles suspended in a continuous fluid, we may be able to use EulerLagrange models to simulate a multiphase flow system. What is your opinion? Please contact our technical support for help. Depending on the type of interaction, it can be either unidirectional (a one-way coupling) or bidirectional (a two-way coupling). This implies that it is numerically impossible to resolve multiphase flows from the smallest to the largest scales using the same mechanistic model throughout the whole range of scales. The multiphysics coupling node provides the coupling between the fluid and the solid structure by accounting for the moving mesh and the deformation of the material as well as for transferring fluid forces to the structure. In separated multiphase flow systems, you can use surface tracking methods to model and simulate the behavior of bubbles and droplets, as well as free surfaces. The fluid flow interfaces generate a number of default plots to analyze the velocity and pressure fields. When you run the application, there are options to change the pipe length, pipe diameter, the number of flow controllers, etc. The CFD Module provides rotating machinery interfaces that formulate the fluid flow equations in rotating frames, available for both laminar and turbulent flow. The Level Set method tracks the interface position by solving a transport equation for the level-set function. Best regards, So, when do we use the different methods? Simulate Single-Phase and Multiphase Flow. Additionally, discontinuous Galerkin formulations are used to conserve momentum, mass, and energy over internal and external boundaries. There is no boundary condition for the free surface using the phase field method. The model is set up based on an example from Lafon et al. Simulation Apps (74) Uncertainty Quantification (0) User Interface (9) Versions. This brings the fins closer to each other, leading to the compression of the fluid between them and expansion of the fluid outside. For the curved boundaries, mesh is allowed to move freely in tangential direction, but the normal components of the solid motion have to be transferred to the moving mesh boundaries. The deformed structure, in turn, acts as a moving wall boundary for the fluid and changes the flow field. Using COMSOL Multiphysics, you can simulate FSI in systems exhibiting different types of dynamics. The Pipe Flow Module is an optional ad d-on package for COMSOL Multiphysics designed to model and simulate fluid flow, heat, and mass transfer in pipes and channels. Model transonic and supersonic flows of compressible fluids in both laminar and turbulent regimes. The effects that need to be taken into account are heat transfer, transport of water vapor, and fluid flow. Multiphase flow may involve the flow of a gas-liquid, liquid-liquid, liquid-solid, gas-solid, gas-liquid-liquid, gas-liquid-solid, or gas-liquid-liquid-solid mixture. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version These models allow you to simulate a wide range of steady and transient turbulent flows. The reason why level set may be preferable for convection dominated problems is because it is a less computationally expensive method, and if there is a lot of convection, then the surface tension effect may be smaller compared to other forces (relatively). What would the most suitable boundary condition be for that free surface? ); I am wondering if the same advantage being able to work with more than one accelerated dispersed phase can be leveraged in Euler-Euler modeling too. The figure above shows the principal difference between the two approaches for separated and dispersed multiphase flow models. The mixture model used to model 5 different sizes of bubbles as the multiphase flow mixture is forced through an orifice. Requires the Structural Mechanics Module, MEMS Module, or Multibody Dynamics Module, Requires the Chemical Reaction Engineering Module, Battery Design Module, or Fuel Cell & Electrolyzer Module. The rising bubble verification problem. Two weeks ago I led a webinar on fluid-structure interaction (FSI) using COMSOL Multiphysics. I am looking forward to the second part! Saul, Dear Saul, Best regards, Modeling Incident Radiation in Radiative Heat Transfer, Model Balanced Heat Transfer, Bake a Better Apple Pie, How to Compute the Projected Area of a CAD File in COMSOL. By choosing appropriate mesh deformation constraints, our aim is to transfer the motion of solid parts to moving mesh. However, it defines one set of NavierStokes equations for each phase. The course covers: Laminar and turbulent flow using finite element analysis The governing equations of mass, momentum and energy Flow for Newtonian and non-Newtonian fluids Meshing requirements In such cases, the system geometry would have to be in an assembly state in order to cope with the large relative movements at the assembly boundaries. Ed. Using a simple numerical method as an expository example, the individual steps of scientific computing are presented: the derivation of the mathematical model; the . In the COMSOL Multiphysics Reference Manual, see Table 2-4 for links to common sections such as Discretization, Consistent Stabilization, Inconsistent Stabilization, and Advanced Settings sections, some of them accessed by clicking the Show button () and choosing the applicable option.You can also search for information: press F1 to open the Help window or Ctrl+F1 to open the Documentation window. At this point, the original phase boundary has to be divided into several boundaries. Left: On the boundaries highlighted, all components of the solid motion are transferred to the adjacent moving mesh boundaries. Thank you for sharing this. As the faces of the elements and the node points are not the same, this may at times affect the accuracy, especially when the relative element sizes across the pair are very different. Here, as the mechanism moves forward along the x-axis, the mesh undergoes stretching in the direction of motion. To this end, we performed finite element simulations with COMSOL Multiphysics, conducted . These models are usually also nice from a numerical point of view. Simulate the Flow of Non-Newtonian Fluids The Polymer Flow Module is an add-on to the COMSOL Multiphysics software that is used for defining and solving problems involving non-Newtonian fluids with viscoelastic, thixotropic, shear thickening, or shear thinning properties. Are there plans to include this functionality in coming Comsol versions. As shown in the figure below, this is possible through the Create pairs check box in the Settings window, which creates identity pairs between pairs of adjacent boundaries. The Free and Porous Media Flow model couples flow in porous domains with laminar or turbulent flow in free domains. We start by giving a brief overview of the latest features and functionality in this module. The motion of the mechanism is initiated by a prescribed rotation of the fins about the central body in a time-dependent manner. The Wet Surface feature is used to implement the source term for the water vapor and to Read More, This non-conventional model of porous media flow utilizes creeping (Stokes) flow in the interstices of a porous media. Ed, Thanks for the great overview. In this archived webinar, learn how to use the COMSOL Multiphysics software and add-on Particle Tracing Module to model the motion of particles in a fluid when they are subjected to an external force. It is possible to introduce interactions between dispersed phases and the continuous phase as well as between the bubbles, droplets, and particles in the dispersed phases. The bubbly flow, mixture, and EulerLagrange multiphase flow models can be combined with all turbulence models in COMSOL Multiphysics. With this model, the formation process of the anode spot is exhibited and demonstrates the non-bipolar flow theory in practice. The test functions are designed to stabilize the hyperbolic terms and the pressure term in the transport equations. One of the most severe problems in power plants, petroleum and petrochemical industries is the accurate determination of phase fractions in two-phase flows. As mentioned in the post, these are certain scenarios where you can use Fluid-Structure Interaction, Pair feature to model the system dynamics. The geometrical changes happening in the fluid domain due to its interaction with the neighboring solid domain are modeled through the arbitrary Lagrangian-Eulerian (ALE) formulation mentioned above. Hello guys, I hope you are all fine and staying safe. As for transferring the motion of the solid elements to the spatial frame, two different types of moving mesh boundary conditions are used, as shown in the figure below. The Read More, This model is intended as a first introduction to simulations of fluid flow and conjugate heat transfer. Which model should I use? Particle Tracing for Fluid Flow (287) Porous Media Flow (400) Chemical (1451) Battery Design (356) . The fluid flow can be modeled with one of the single-phase flow or multiphase flow interfaces. The dispersed phase is allowed to accelerate, and there is no real limit in the volume fractions for the different phases. The COMSOL software provides an easy solution for this problem with the Fluid-Structure Interaction, Pair multiphysics coupling, available as of version 5.4. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' (or the latest version After adding the multiphysics interface, the Model Builder looks like the figure below. For more information about different mesh boundary conditions, you can refer to COMSOL Multiphysics Reference Manual, Deformed Geometry and Moving Mesh chapter. At this moment I am modelling a multiphase problem myself; spreading of a droplet of water (surrounded by air) between two flat plates. I do not completely understand your question. Is there a possibility that using this Accumulator feature could help me to achieve density-based separation? Every business and every simulation need is different. The COMSOLMultiphysics software provides a powerful set of built-in functions and operators, such as functions for uniform and Gaussian random distributions and a very useful sum operator. Computational Fluid Dynamics (CFD) Blog Posts . Two-Phase Flow with Fluid-Structure Interaction, Natural Convection Cooling of a Vacuum Flask. The geometrical changes in the fluid domain are incorporated in the model by assigning a deforming domain to the fluid part. Oussamane. The DES models are applicable to 3D, time-dependent, incompressible single-phase flows. Find examples and demonstrations on the COMSOL Blog. Compressible hydraulic transients and acoustic waves can also be modeled using the Water Hammer interface and Pipe Acoustics interface, respectively. I use the level-set method to track the liquid-liquid interface, and use the TDS module to study the mass transfer process. Currently, I am working with two-phase liquid -liquid slug flows in microchannels with an aim of studying the internal circulations within them using level set . Nonisothermal PEM Fuel Cell. Best regards, Computational Fluid Dynamics (CFD) Blog Posts . The CFD Module provides four different (in principle) models: The bubbly flow model is obviously used for gas bubbles in liquids. Thank you. To achieve that the wall must me moved with the final steady state bubble velocity. The temperature profile is obtained by coupling Heat Transfer and Navier-Stokes Modules of COMSOL Multiphysics. I need to simulate the non-isothermal fluid flow of a water/gas mixture in a heated pipe. The mixture model is able to handle any combination of phases and is also computationally inexpensive. Generally, when a solid object is placed in the path of a fluid, the fluid applies pressure and viscous forces on the boundaries of the structure, leading to its deformation. Such models may be referred to as separated multiphase flow models in the COMSOL software. Best regards, Or could you point to an example where this is added manually (maybe via support!?)? I want to simulate a biological Methanation process. Both the mixture model and the bubbly flow model assume that the dispersed phase is in equilibrium with the continuous phase; i.e., the dispersed phase cannot accelerate relative to the continuous phase. Methods used to describe such models are usually referred to as surface tracking methods. First of all, Great tutorial! Any multiphysics problem where a solid and fluid are coupled to influence the behavior of each other falls under the class of fluid-structure interaction (FSI).

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