Meshes, Numerics & Parallel Processing

Ansys Fluent software uses unstructured mesh technology. The mesh can consist of elements in shapes such as quadrilaterals and triangles for 2-D simulations and hexahedra, tetrahedra, polyhedra, prisms and pyramids for 3-D simulations. Sophisticated numerics ensure accurate results on any combination of mesh types, including meshes with hanging nodes and non-matching mesh interfaces. Ansys Fluent’s solvers run robustly and efficiently for all physical models and flow types, steady-state or transient and incompressible through hypersonic. Advanced parallel processing capabilities, available on Windows, Linux, and UNIX platforms can be used to run simulations on multi-core processors with multiple processors on a single machine and multiple machines on a network. Using 64-bit technology, Ansys Fluent can run parallel calculations on meshes consisting of a billion cells or more. Advanced dynamic load balancing automatically redistributes calculations between processors in order to gain the most efficiency. No matter how many processors are used for parallel calculation, 2 to 1024 or more, Ansys Fluent ensures that CFD calculations benefit from the additional processing power.

Press release: Ansys Breaks 1 Billion Cell Barrier

Scaling of Ansys Fluent 12.0 software is nearly ideal up to 1,024 processors and 78 percent of ideal at 2,048 processors. Data courtesy SGI, based on the SGI Altix® ICE 8200EX using Intel Xeon® quad-core processors with Infiniband®.

Dynamic & Moving Mesh

The dynamic mesh capability in Ansys Fluent meets the needs of challenging applications, including in-cylinder flows, valves and store separation. Several different mesh rebuilding schemes, including layering, smoothing and remeshing, can be used for different moving parts within the same simulation as needed. Only the initial mesh and a description of the boundary movement are required. A built-in six-degrees-of-freedom solver is also available for applications with unconstrained motion, including store separation, ship hydrodynamics, missile launch, and tank sloshing. Dynamic meshing is compatible with a host of other models including Ansys Fluent’s suite of spray breakup and combustion models and multiphase models including those for free surface prediction and compressible flow.

Ansys Fluent also provides sliding mesh and multiple reference frame models that have a proven track record for mixing tanks, pumps, and turbomachinery.

Click image to view animation of flow patterns in a 4-stroke internal combustion engine

Internal combustion engine modeling using Ansys Fluent moving and deforming mesh models and post-processed using Ansys CFD-Post software

Turbulence & Acoustics

Ansys Fluent offers an unparalleled breadth of turbulence models such as; several versions of the time-honored k-epsilon model, the k-omega model and the Reynolds stress model (RSM). Recent advancements in turbulence modeling have lead to the implementation of additional models like turbulent transition models, important for detailed modeling of the transition from laminar to turbulent flow that occurs near boundaries, and a Scale-Adaptive Simulation (SAS) turbulence model (beta functionality) which provides a steady solution in stable flow regions while resolving turbulence in transient instabilities like massive separation zones, without an explicit grid or timestep dependency. Recent increases in computer power, coupled with decreases in computing cost, have made the large eddy simulation (LES) model and the more economical detached eddy simulation (DES) model very attractive choices for industrial simulations. For acoustics, ANSYS FLUENT can compute the noise resulting from unsteady pressure fluctuations in several ways. Transient LES predictions for surface pressure can be converted to a frequency spectrum using the built-in Fast Fourier Transform (FFT) tool. The Ffowcs-Williams & Hawkings acoustics analogy can be used to model the propagation of acoustics sources for various objects, ranging from exposed bluff bodies to rotating fan blades. Broadband noise source models allow acoustic sources to be estimated based on the results of steady-state simulations.

Click to view larger image of vortex structures generated by aircraft landing gear

Vortex structures generated by aircraft landing gear

Heat Transfer, Phase Change & Radiation

Heat transfer accompanies many fluid flow phenomena and Ansys Fluent offers a comprehensive suite of options for convection, conduction and radiation. Several radiation models are available, including the P1 and Rosseland models for optically thick, participating media, and the view-factor based surface-to-surface model for non-participating media. The discrete ordinates (DO) model is also available and suitable for any medium, including glass. Additionally, a solar load model is available for climate control simulations and two heat exchanger models are available. Other capabilities closely associated with heat transfer include models for cavitation, compressible liquids, shell conduction, real gasses and wet steam.

Click to view larger flow modeling image of an uranium melt and solidification in a failed reactor

Uranium melt and solidification in a failed reactor

Reacting Flow

Chemical reaction modeling, especially in turbulent conditions, has been a hallmark of Ansys Fluent software since its inception. Ansys Fluent uses newer models such as the eddy dissipation concept, PDF transport and stiff finite rate chemistry models, as well as mature models such as the eddy dissipation, equilibrium mixture fraction, flamelet and premixed combustion models. In-situ adaptive tabulation (ISAT) can be used in conjunction with either the EDC or PDF transport models and provides acceleration for turbulent finite rate chemistry, speeding up calculations by an order of magnitude or more. The standard reacting flow models available in Ansys Fluent can be used to tackle a vast array of gaseous, coal and liquid fuel combustion simulations. Special models for the prediction of SOx formation and NOx formation and destruction are also available. Ansys Fluent’s surface reaction capability allows for reactions between gas and surface species, as well as between different species, so that deposition and etching can be rigorously predicted. Ansys Fluent’s reaction models can also be used in conjunction with the real gas model and LES and DES turbulence models. 

Click to view larger CFD image of a Low NOx burner simulation
Low NOx burner
Courtesy of GE Energy


Ansys Fluent is a leader in multiphase modeling technology. Its varied capabilities allow engineers to gain insight into equipment that is often difficult to probe. Ansys Fluent makes use of the Eulerian multiphase model with its separate sets of fluid equations for interpenetrating fluids or phases, as well as offering a more economical mixture model. Both models can also handle granular flows. Several other multiphase models are also standard in Ansys Fluent. For some multiphase applications such as spray dryers, liquid fuel sprays, continuous fiber drawing and coal furnaces the discrete phase model (DPM) can be used. The volume of fluid model is available for free surface flows, such as ocean waves, where the prediction of the interface is of interest. The cavitation model has proven useful for robustly modeling hydrofoils, pumps and fuel injectors. Several population balance models are also available for modeling size distributions.

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Bubbles in a fluidized bed

Post-Processing and Data Export

Ansys Fluent’s post-processing tools can be used to generate meaningful graphics, animations and reports that make it easy to convey CFD results. Shaded and transparent surfaces, pathlines, vector plots, contour plots, custom field variable definition and scene construction are just some of the post-processing features that are available. Solution data can be exported to Ansys CFD-Post, third party graphics packages, or to CAE packages for additional analysis. Under the Ansys Workbench environment, Ansys Fluent solution data can be mapped to Ansys simulation surfaces for use as thermal or pressure loads. In standalone mode, Ansys Fluent, can also map structural and thermal loads on surfaces and temperatures in volumes from Ansys Fluent to 3rd-party FEA meshes.

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Polyhedral mesh and pressure distribution on an F1 car post-processed using Ansys CFD-Post Software

Customized Tools

User-defined functions are a popular option for users wanting to customize Ansys Fluent. Comprehensive documentation and a number of tutorials are available, as is full technical support. The Ansys global consulting network can provide or help create templates for the repeated setup of any equipment. Add-on modules for many special applications are available, such as PEM and solid oxide fuel cells and magnetohydrodynamics.

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Anisotropic diffusion of a drug from a stent into a capillary wall