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10 questions to ask yourself when tackling your first (or a new) Multiphase CFD project
Oct25

10 questions to ask yourself when tackling your first (or a new) Multiphase CFD project

By virtue of the many physical processes we are often attempting to simulate in a virtual environment, CFD can be a complex beast.  To accurately account for all real-world behaviour, the CFD engineer must consider the applicability of a large number of physical effects, including complex turbulence, compressibility, various modes of heat transfer and, last but certainly not least, the interaction of multiple phases comprising liquid, gaseous and solid components.   Even if you have mastered all of your geometry and meshing requirements, and undertaken many years of single-phase CFD simulations, it can still be a daunting task when you are asked to tackle your first multiphase CFD problem.  Before you begin, we recommend that you ask yourself the following:   [1]  For each phase in your system (gas/liquid/solid), make a decision on whether it should be considered as a continuous phase (which assumes all regions of this particular material are connected) or as a discrete phase that is dispersed throughout the domain (e.g. droplets, particles or bubbles).   [2] For each continuous phase, decide whether the flow is laminar or turbulent by evaluating a characteristic Reynolds number for your problem.   [3] Determine the Stokes number for each dispersed component and decide if it will follow the continuous flow closely (smaller Stokes numbers, typically < 0.01) or move largely independently of it (larger Stokes numbers, typically >1).   [4] For each dispersed phase, based on your understanding of the real physics, decide whether it is necessary to model a wide range of sizes (of droplets/particles), or whether your modelling goals can be achieved by modelling the system with a single size or just a few representative size classes.   [5] Decide whether assessing changes to the characteristic size of the dispersed phase (e.g. increasing/decreasing droplet or bubble diameter) will be important for your CFD modelling goals.   [6] If so, assess the mechanism that is causing this breakup or coalescence. The Weber number describes the ratio of inertial forces to surface tension forces acting on the droplet, and can be used to help you decide the dominant breakup mechanism.  Typically the droplet will be stable for Weber Numbers less than 6.   [7] Review whether gravitational effects are important. The Bond number helps you assess this as it describes the ratio of gravitational forces to surface tension forces.   [8] Review whether surface tension effects are important. Check your Capillary number, which is the ratio of viscous forces to surface tension forces.  The appropriate ranges where surface tension can be neglected can be heavily problem dependent, so please contact us if you require for more information on this area.   [9]...

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Learn from the Expert: Training in Multiphase Flow Modelling with Dr. Markus Braun, ANSYS Inc.
Aug31

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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