Recent advances in Multiphase Flow Modelling
What's changed in the world of multiphase flow modelling in the past 2-3 years? As always, an understanding of the physics of the system that you are modelling remains the number one priority, however, a number of new developments will help you address a wider range of multiphase flows and in a faster and more effective way.
(Part 2) 10 Useful Tips on selecting the most appropriate multiphase flow CFD models
As we discussed in our previous post, the first step when tackling a multiphase CFD problem is to identify the key characteristics of your physical system. Once you've done this (using our checklist if you are still new to multiphase CFD), you can begin to make informed decisions on what multiphase modelling approaches to use. We've compiled the following guidelines based on the decades of experience that LEAP has developed while helping customers in Australia and New Zealand to solve multiphase CFD problems, particularly companies and researchers in the minerals, process and energy industries: [1] If your problem involves a distinct free surface between two fluids (typically liquids), then the "Free surface" model in CFX or "Volume of Fluid / VOF" model in Fluent should be selected. Both of these methods allow an interface to be solved in steady-state (if it achieves an equilibrium state) or tracked over time in a transient simulation. [2] If your system involves a dilute system of droplets or particles (maximum volume fractions less that ~5%) and you need to track typical trajectories to follow physical processes (such as drying, evaporation, combustion etc.), then you need to use a Lagrangian approach: this is termed the Discrete Particle Model (DPM) in Fluent & the Particle Transport model in CFX. Both codes have an extensive range of in-built models related to the particle physics, so we encourage you to review these options in the manual before you start and contact LEAP if you have specific questions. [3] If your Stokes number is small, then the particles will quickly reach equilibrium with the fluid flow and travel at their terminal velocity. In this case, the Mixture model in Fluent or the Algebraic Slip Model (ASM) in CFX are good choices for a balance of accuracy and speed. The reason that these models greatly reduce computational time is that they only solve a single momentum equation and the other velocities are obtained by calculating the particle slip velocity. [4] If your Stokes number is larger, then an Eulerian model will be needed. An Eulerian multiphase model will solve a separate velocity field for each phase, which is the most general approach and allows complete freedom as to the behaviour of each phase within your domain. [5] If you have solid particles present, then you will need to understand the maximum packing density for your system (incorporating particle shape and size distribution), and then decide how you are going to enforce it. If the packing limit of your particles is not likely to be reached (or is unimportant to your simulation), then the Eulerian Granular models can be used which are based on solids pressure models and kinetic...
Learn from the Expert: Training in Multiphase Flow Modelling with Dr. Markus Braun, ANSYS Inc.
LEAP Australia is pleased to announce a visit to Australia by Dr Markus Braun, Team Leader, Multiphase Development, ANSYS Inc. Dr. Braun will be presenting a two-day course in Melbourne on Multiphase Flow Modelling, in conjunction with his visit to the 2012 CSIRO Conference on CFD in the Minerals and Process Industries. The training will be held in Melbourne on December 13-14, 2012. Who should attend? This course is a rare opportunity for all engineers & managers who are working with CFD simulations involving multiphase flow, in an industrial or research environment. The course will comprise a mixture of lectures and example case studies which will allow attendees to gain a first hand knowledge of all multiphase modelling approaches available in ANSYS CFD and their application to various industrial problems. ABOUT THE PRESENTER Dr. Markus Braun studied mechanical engineering at RWTH Aachen, receiving his Diploma in 1989. He finished his studies with the award of the Springorum Denkmünze for excellent students at RWTH Aachen. Markus then joined the Institute for Heat Transfer at RWTH Aachen where he worked on condensation of multi component mixtures and simulation of continuous fiber spinning. In 1995, Markus joined FLUENT Deutschland GmbH as a Support and Consulting Engineer. In 2000, he took over development of the Euler/Lagrange model in FLUENT and became the head of the functional group of the "Discrete Phase Model" and supervised the development team in Germany working on models to describe multiphase flows, turbulence, plasma flows, fuel cells, and numerical schemes. In 2006, Markus became the technical lead for development in Euler/Lagrange multiphase flow modeling at ANSYS Inc. For an overview of Multiphase Models available using ANSYS CFD, please click here. TO REGISTER: Click this link to proceed to LEAP's Training Registration Melbourne: 2-day Training Course in Multiphase Flow Modelling Date: Thurs 13th to Fri 14th Dec, 2012 Venue: MCEC, Southbank, Melbourne, Vic A discount will also be available to organisations submitting 2 or more registrations. To enquire about the multiple registration discount, please click here and fill out your...
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