Multiflow is a term used to describe the flow of multiple phases (solid, liquid, or gas) in a system. In Ansys Fluent, you can define multiflow by choosing one of the available multiphase models, depending on the type and behavior of the phases involved. Some of the multiphase models in Ansys Fluent are:
- Volume of Fluid (VOF) model: This model is suitable for tracking the interface between two or more immiscible fluids, such as water and air. You can use this model to simulate problems such as sloshing tanks, breaking waves, or bubble columns¹²³.
- Eulerian model: This model is suitable for simulating dispersed multiphase flows, such as solid particles in a gas or liquid stream. You can use this model to simulate problems such as fluidized beds, cyclone separators, or pneumatic conveying⁴⁵.
- Mixture model: This model is suitable for simulating dilute multiphase flows, where the phases are well mixed and have similar velocities. You can use this model to simulate problems such as sediment transport, spray drying, or blood flow⁴⁵.
To define multiflow in Ansys Fluent, you need to follow these steps:
- Go to Models > Multiphase and select the desired multiphase model from the drop-down list.
- Specify the number and type of phases in your system.
- Define the properties and interactions of each phase, such as density, viscosity, surface tension, drag force, etc.
- Set the boundary conditions and initial conditions for each phase.
- Solve the problem and visualize the results.
For more details and examples on how to define multiflow in Ansys Fluent, you can watch some of the video tutorials available online¹²³. I hope this helps you with your problem. 😊
Source: Conversation with Bing, 10/18/2023
(1) #ANSYS FLUENT - Multiphase Flow Tutorial - YouTube. https://www.youtube.com/watch?v=TLx8UemITgY.
(2) ANSYS Fluent Tutorial | Multiphase flow in an Inclined Pipe | Two Phase Flow in an Inclined Pipe VOF. https://www.youtube.com/watch?v=22dGJtp0CQY.
(3) Ansys Fluent Tutorial for beginners | Multiphase Flow | Three Phases | Ansys Workbench. https://www.youtube.com/watch?v=QgQTaXuPmbI.
(4) Introduction to Multiphase Flow Modeling using Ansys Fluent | Ansys .... https://www.youtube.com/watch?v=Uwu4QRmRstk.
(5) Multiphase Flow Modeling Using ANSYS FLUENT | LearnCAx. https://www.learncax.com/courses/by-software/multiphase-flow-modeling-using-ansys-fluent-detail.
(6) ANSYS FLUENT 12.0 User's Guide - 7.3.11 Outflow Boundary Conditions - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node247.htm.
(7) Ansys Fluent Multiphase Flow Simulation | Ansys Training. https://www.ansys.com/training-center/course-catalog/fluids/ansys-fluent-multiphase-flow-modeling.
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How do I choose the right multiphase model for my problem?
Choosing the right multiphase model for your problem depends on several factors, such as:
- The type and behavior of the phases involved (solid, liquid, or gas)
- The volume fraction and distribution of each phase
- The degree of interphase coupling and interaction
- The computational cost and accuracy of the model
(1) ANSYS FLUENT 12.0 Theory Guide - 16. Multiphase Flows - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node288.htm.
(2) ANSYS FLUENT 12.0 Theory Guide - 16.2 Choosing a General Multiphase Model. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node292.htm.
(3) ANSYS FLUENT 12.0 Theory Guide - 16.2.1 Approaches to Multiphase Modeling. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node293.htm.
(4) Ansys Fluent Multiphase Flow Simulation | Ansys Training. https://www.ansys.com/training-center/course-catalog/fluids/ansys-fluent-multiphase-flow-modeling.
Sure, I can give you some examples for each multiflow model in Ansys Fluent. Here are some of them:
- Volume of Fluid (VOF) model: This model is suitable for tracking the interface between two or more immiscible fluids, such as water and air. You can use this model to simulate problems such as sloshing tanks, breaking waves, or bubble columns¹²³. For example, you can use the VOF model to simulate the flow of water and air in a 135 degree inclined pipe with a small opening at one face and a large outlet³. You can watch a video tutorial on how to set up and solve this problem using Ansys Fluent [here](^3^).
- Mixture model: This model is suitable for simulating dilute multiphase flows, where the phases are well mixed and have similar velocities. You can use this model to simulate problems such as sediment transport, spray drying, or blood flow⁴⁵. For example, you can use the mixture model to simulate the flow of water, air, and oil in a three-phase separator⁵. You can watch a video tutorial on how to set up and solve this problem using Ansys Fluent [here](^2^).
- Eulerian model: This model is suitable for simulating dispersed multiphase flows, such as solid particles in a gas or liquid stream. You can use this model to simulate problems such as fluidized beds, cyclone separators, or pneumatic conveying⁴⁵. For example, you can use the Eulerian model to simulate the flow of air and coal particles in a coal combustion chamber⁵. You can watch a video tutorial on how to set up and solve this problem using Ansys Fluent [here](^4^).
I hope these examples help you understand the different multiflow models in Ansys Fluent. 😊
Source:
(1) ✅ #ANSYS FLUENT - Multiphase Flow Tutorial. https://www.youtube.com/watch?v=TLx8UemITgY.
(2) Ansys Fluent Tutorial for beginners | Multiphase Flow | Three Phases | Ansys Workbench. https://www.youtube.com/watch?v=QgQTaXuPmbI.
(3) ANSYS Fluent Tutorial | Multiphase flow in an Inclined Pipe | Two Phase Flow in an Inclined Pipe VOF. https://www.youtube.com/watch?v=22dGJtp0CQY.
(4) ANSYS Fluent Tutorial | Multiphase flow in an Inclined Pipe | Two Phase Flow in an Inclined Pipe VOF. https://www.youtube.com/watch?v=22dGJtp0CQY.
(5) Introduction to Multiphase Flow Modeling using Ansys Fluent | Ansys .... https://www.youtube.com/watch?v=Uwu4QRmRstk.
(6) ANSYS FLUENT 12.0 Theory Guide - 16. Multiphase Flows - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node288.htm.
(7) Ansys Fluent Tutorial for beginners | Multiphase Flow | Three Phases | Ansys Workbench. https://www.youtube.com/watch?v=QgQTaXuPmbI.
(8) Introduction to Multiphase Flow Modeling using Ansys Fluent | Ansys .... https://www.youtube.com/watch?v=Uwu4QRmRstk.
(9) ANSYS FLUENT 12.0 Theory Guide - 16.1.2 Examples of Multiphase ... - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node291.htm.
What are some limitations of multiphase models?
Some limitations of multiphase models are:
- They require more computational resources and time than single-phase models, especially for complex multiphase flows with strong interphase coupling and interaction¹.
- They may not be available or compatible with some features or solvers in Ansys Fluent, such as the density-based solver, the Reynolds Stress turbulence model, the inviscid flow, the melting and solidification, the streamwise periodic flow, etc²³.
- They may not have exact analytical solutions or reliable interphase laws for some cases, such as non-linear conduction equations, phase change phenomena, or granular flows.
- They may not capture some important physical effects or phenomena, such as phase separation, coalescence and breakup, cavitation, etc.
These limitations may affect the accuracy and validity of the multiphase models for some applications. Therefore, it is important to choose the appropriate model based on the characteristics and behavior of the multiphase flow, and to validate the results with experimental data or other methods.
Source:
(1) 16.4.1 Overview and Limitations of the Mixture Model - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node309.htm.
(2) 16.5.1 Overview and Limitations of the Eulerian Model - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node320.htm.
(3) Multiphase Flows: Basic Physics and Engineering Modeling. https://staff.polito.it/pietro.asinari/teaching/NHT_Asinari_Multiphase_v1.5.PDF.
Can you recommend a good book on multiphase flows?
Sure, I can recommend some good books on multiphase flows. Multiphase flows are complex phenomena that involve the interaction of two or more phases (solid, liquid, or gas) in a system. They have many applications in engineering, science, and industry, such as fluidized beds, oil and gas production, nuclear reactors, spray combustion, etc. To understand and model multiphase flows, you need to have a solid background in fluid mechanics, thermodynamics, heat and mass transfer, and numerical methods.
There are many books on multiphase flows available in the market, but some of them are more suitable for beginners, while others are more advanced or specialized. Depending on your level of interest and expertise, you can choose from the following books:
- **Fundamentals of Multiphase Flow** by Christopher E. Brennen¹: This book is a good introduction to the basic concepts and principles of multiphase flow. It covers topics such as single-particle motion, bubble dynamics, cavitation, boiling and condensation, flow patterns, homogeneous flows, sprays, granular flows, drift flux models, system instabilities, and kinematic waves. It also provides some examples and exercises for each chapter.
- **Computational Methods for Multiphase Flow** by Andrea Prosperetti and Grétar Tryggvason²: This book is a comprehensive guide to the numerical methods and techniques for simulating multiphase flows. It covers topics such as direct numerical simulations, immersed boundary methods, structured grid methods, finite element methods, lattice Boltzmann models, boundary integral methods, averaged equations, point-particle methods, segregated methods, and coupled methods. It also provides some case studies and applications for each method.
- **Multiphase Flow Analysis Using Population Balance Modeling: Bubbles, Drops and Particles** by Guan Heng Yeoh³: This book is a specialized book on the population balance modeling approach for multiphase flows. It covers topics such as population balance equations, breakup and coalescence models, interfacial area transport equations, bubble column reactors, fluidized beds, spray drying systems, etc. It also provides some software tools and codes for implementing the models.
- **Multiphase Flow Dynamics** by Nikolay Ivanov Kolev⁴: This book is an advanced book on the theoretical and experimental aspects of multiphase flow dynamics. It covers topics such as thermodynamics of multiphase systems, interfacial phenomena, phase change processes, multiphase turbulence models,
multiphase flow instrumentation and measurement techniques,
multiphase flow safety issues,
etc. It also provides some examples and problems for each topic.
These are some of the best books on multiphase flows that I can recommend to you. I hope you find them useful and interesting. 😊
Source:
(1) Fundamentals of Multiphase Flow - Cambridge University Press & Assessment. https://www.cambridge.org/core/books/fundamentals-of-multiphase-flow/FC7E6D7E54AC9D1C178EDF88D6A75FFF.
(2) Computational Methods for Multiphase Flow - Cambridge University Press .... https://www.cambridge.org/core/books/computational-methods-for-multiphase-flow/B2BD97E62BA30AA80779E5E54B47A5B4.
(3) 12 Best Books on Multiphase Flow - Sanfoundry. https://www.sanfoundry.com/best-reference-books-multiphase-flow/.
(4) Multiphase Flow Handbook - Google Books. https://books.google.com/books/about/Multiphase_Flow_Handbook.html?id=BgMUjwEACAAJ.
(5) Multiphase Flow Handbook | Efstathios Michaelides, Clayton T. Crowe, J. https://www.taylorfrancis.com/books/edit/10.1201/9781315371924/multiphase-flow-handbook-efstathios-michaelides-john-schwarzkopf-clayton-crowe.
(6) https://doi.org/10.1017/CBO9780511807169.
(7) https://doi.org/10.1017/CBO9780511607486.
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