Over the past few decades, ANSYS Fluent has become the gold standard for CFD. Whether you analyze basic heat transfers or fluid flows or work with complex geometries that have transient reacting flows, ANSYS Fluent should be an integral part of your product optimization and designing process.
Table of Contents (Click to navigate)
- What is ANSYS Fluent?
- Creating a standalone Fluent system
- Creating multiple or cross-linked Fluent systems
- Workflows inside ANSYS Fluent
- ANSYS MeshingTM
- Setup and Solution
- Results (CFD-Post)
- Moving forward
What is ANSYS Fluent?
ANSYS Fluent is a CFD software that is particularly used for fluid flow modeling and heat transfer. Fluent was acquired by ANSYS Inc in 2006 for $299 million. The software has undergone various changes and improvements to cater to the needs of the industry. With this CFD software, you can model and simulate all types of fluid processes as well as Fluid-structure Multiphysics interactions. ANSYS Fluent also has broad physical modeling capabilities that are needed for fluid flow, heat transfer, turbulence and reactions for industrial applications.
With unmatched accuracy and scope, ANSYS Fluent is the CFD software of choice by many companies and academics all over the world. Developed by renowned engineers and experts from all over the globe, you can always be confident in your solution as you develop better quality products faster with reduced risk and time to market.
ANSYS Fluent is a highly complex CFD package that caters to the needs of every individual. Being a diverse software, it is impractical to go through each aspect of fluent in this tutorial. What is possible is to give you a surface level understanding of the software for you to get familiar with it.
Creating a standalone Fluent system
As discussed in previous articles, ANSYS is an engineering simulation software that caters to the needs of all sorts of engineering out there. Therefore, it has a long list of analysis systems present in it. For the fluid flow, we have two simulation systems – CFX and Fluent. In this comprehensive tutorial, we will be looking into the Fluent system only.
A complete list of Analysis systems in ANSYS
To create a standalone Fluent system in ANSYS, click over the Fluid Flow (Fluent) in the Analysis Systems. Once selected, drag it to the project schematics and drop it. This will create a single standalone ANSYS fluent workflow in the project schematics.
Drag and drop the Fluid Flow (Fluent) to create a fluent standalone system
Creating multiple or cross-linked Fluent systems
To create multiple Fluent systems, you can drag and drop multiple Fluent systems in the project schematics. The following project schematics shows the Fluent systems for a wing with varying Angle of Attacks (AOA).
The snapshot shows multiple ANSYS Fluent workflows under one project schematics
ANSYS Fluent is also fully integrated and completely customizable within ANSYS Workbench. This allows the users to adopt different ANSYS capabilities to solve complex challenges with ease and in comparatively less time.
The snapshot shows cross-liked workflow between Fluent and Transient Structural to carry out Fluid Structural Interface (FSI)
Workflows inside ANSYS Fluent
Each Fluent system has a set of five components. Each component has a specific set of functions and is necessary for them to be set correctly for the complete Fluent system to run correctly. Each component has its own significance which is briefly explained as follows;
‘Geometry’ is the ANSYS Fluent workspace for creating 2D or 3D models that need to be processed further for their heat transfer or fluid flow. The ‘geometry’ has similar CAD designing workspace like Autodesk Inventor and SOLIDWORKS. The older versions of ANSYS (older than ANSYS 19) offers a conventional ‘Design Modeler,’ whereas the new ANSYS 19 and above offers Design Modeler and SpaceClaim. SpaceClaim is one of the many new features added to ANSYS Fluent. To see the full list of new ANSYS 19 features, refer to this article.
Geometries for ANSYS Fluent can also be imported from other CAD software. For importing geometries from other software, the files must be imported as a .stp format.
Meshing is an integral part of all the analysis systems in ANSYS. Meshing allows the geometries to be broken into small polygons so that each polygon can be processed separately to generate the results. The finer the mesh, the better the results. However, refining mesh too much can lead to high processing times. Therefore, engineers must determine the sweet spot between the density of the mesh and the accuracy of the result.
Refined meshing around a NACA 0012 airfoil in a wind tunnel
Setup and Solution
Double-clicking over setup launches the ANSYS Fluent. Before Fluent opens, a Fluent Launcher opens to set the pre-launch settings. It allows you to select your dimensions, display options, processing options and much more. One of the many great features of ANSYS Fluent is to its ability to use parallel processing or multiple processors of HPC.
After the ANSYS Fluent has opened, the work tree and the task page can be seen on the left side of the window. The tree and task page includes the setup, solution, boundary conditions, cell zone condition and all other variables set on the geometry to generate fluid flow or heat transfer result.
Fluent contains a list of different models that the users can use according to their need. For example, if the user needs to determine viscous flow over an object he can choose from several different preset formulations to generate their results. The multiphase processing, energy in the system, acoustics, discrete phases can all be set here. Below is a snapshot of setting up the viscous flow with a standard k-epsilon model under standard wall functions over an airfoil in a wind tunnel. It must be noted that there are no fixed set of commands that can be keyed in fluent to generate results. For every type of CFD simulation, there are a different set of selections to make to generate reliable results for that model.
The different set of models and other inputs from the user
After the model for the simulation is selected, the user may select the type of fluid and the solid on which the fluid will be interacting. ANSYS Fluent has a wide array of preset fluids and solids to choose from their database. If you are testing a new solid or fluid, you can always set your custom material by setting its properties.
The snapshot shows a selection of fluid for the solution from a drop-down menu. ANSYS database has over 1000 fluids and solids to choose from.
Setting up boundary conditions is also an important part in the CFD simulation. Boundary conditions help the software determine the fluid inlets and outlets and how each surface will behave when in contact with the fluid. The values and type of inlets and outlets can all be selected by the user. The user can also select a wide array of turbulence models if the flow is not laminar.
The snapshot shows a velocity inlet of a wind tunnel with a velocity magnitude of 40 m/s
After all the variables are set, the solution is then processed via ‘Run Calculation.’ This is the part where the iterations of formulations are carried out so that they can be converged. Here, the solver uses complex mathematical equations to generate the results. For results to be precise, it is necessary for the calculations to converge.
Results CFD Post
The ‘results’ is a CFD post-processor for Fluent. Under CFD-post, the outputs from the variables that are set up in Fluent can be visually seen and analyzed. CFD post is an important component and essential to the users as here they can see a simulated demonstration of how their product will behave in real life scenarios.
Users can make contours, streamlines, vectors, particle tracking and many other different visual features that allows the designers and engineers to see how their product will behave in actual condition.
Velocity vectors around a wing at AOA=4°
The contours also help us visually see the effects of the fluids over the body. For the contours showed below, the object is tested in a virtual wind tunnel and analyzed on how different pressure regions are formed over it due to the wind. This way the design engineers can visually evaluate their design and make tweets as needed.
Regions of low and high pressure forming over an object
Streamline and vortices over a wing at high AOA
There are different sets of inputs that the user can put in to get their desired results in the CFD-post. The above set of results was obtained via the following commands;
As stated earlier, ANSYS Fluent is a diverse simulation software which covers a vast spectrum of CFD. Though covering all the topics into one short tutorial is virtually impossible, we are ready to assist you in your queries and questions by making new ANSYS Fluent tutorials for your needs. If you need to learn something new in ANSYS or have any questions, feel free to comment below. Our contributors will make ANSYS fluent tutorials for you right away.
Sohaib Alam is an Undergraduate at the University of Sunderland specializing in Mechanical Engineering. Sohaib specializes in Physics among many other engineering subject matter. He focuses his writing on ANSYS and AutoCAD Inventor.