ANSYS CFX Features
predict, with confidence, the impact of fluid behavior on your product.
ANSYS CFX is integrated into the unified ANSYS Workbench platform, which forms the foundation for the industry’s broadest and deepest suite of advanced engineering simulation technology. This easy-to-use platform provides access to bi-directional parametric CAD connections, powerful geometry and meshing tools, an automated project-level update mechanism, pervasive parameter management, multiphysics simulation management, and integrated optimization tools. As a result of these tight connections, ANSYS CFX delivers benefits that include the ability to:
- Quickly prepare product/process geometry for flow analysis without tedious rework
- Avoid duplication through a common data model that is persistently shared across physics — beyond basic fluid flow
- Easily define a series of parametric variations in geometry, mesh, physics and post-processing, enabling automatic new CFD results for that series with a single mouse click
- Improve product/process quality by increasing the understanding of variability and design sensitivity
- Easily set up and perform multiphysics simulations
The bottom line: ANSYS CFX delivers unprecedented productivity in CFD simulation, enabling Simulation Driven Product Development.
ANSYS CFX software provides complete mesh flexibility, including the ability to solve flow problems using unstructured meshes that can be generated about complex geometries with relative ease. Supported mesh types include triangular, quadrilateral, tetrahedral, hexahedral, pyramid, and prism (wedge). ANSYS Workbench allows you to import your CAD geometry, prepare it for CFD use in ANSYS DesignModeler and mesh it automatically or manually with the ANSYS Mesh component.
ANSYS CFX runs robustly and efficiently for all physical models and flow types including steady-state or transient, incompressible or compressible flows (from low subsonic to hypersonic), laminar or turbulent flows, Newtonian or non-Newtonian flows, and ideal or real gases.
For decades, ANSYS CFX software has focused on a solution strategy using a coupled algebraic multi-grid techniques that delivers fast and reliable convergence that is completely scalable with mesh size, one that requires no user input or numerical adjustments. In addition, it is insensitive to high-aspect ratio mesh cells to allow boundary layers to be captured efficiently and accurately. For maximum accuracy in all simulations, it uses second-order advection schemes by default. The solver delivers excellent performance on all types of problems and is particularly powerful in flows in which inter-equation coupling is significant. Examples of this include rotating flow with strong Coriolis terms, combusting flows and high-speed flow with strong pressure gradients.
Careful discretization is necessary to provide robust and accurate answers to the range of situations encountered in industrial CFD. ANSYS CFX software's default high-resolution discretization delivers on both counts. The adaptive central bounded numeric scheme locally adjusts the discretization to be as close to second order as possible while ensuring stable simulation.
The vast majority of industrial flows are turbulent, so ANSYS CFX software has always placed special emphasis on providing leading turbulence models to capture the effects of turbulence accurately and efficiently.
For statistical turbulence models, ANSYS CFX provides numerous common two-equation models and Reynolds–stress models. However, particular focus is placed on the widely tested shear stress transport (SST) turbulence model, as it offers significant advantages for non-equilibrium turbulent boundary layer flows and heat transfer predictions. The SST model is as economical as the widely used k-ε model, but it offers much higher fidelity, especially for separated flows, providing excellent answers on a wide range of flows and near-wall mesh conditions. ANSYS CFX complements the SST model with numerous other turbulence modeling innovations, including an automatic wall treatment for maximum accuracy in wall shear and heat transfer predictions and a number of extensions to capture effects like streamline curvature.
ANSYS CFX also has innovative capabilities in the area of laminar-to-turbulent transition modeling. Using CFD to predict the location where the laminar boundary layer becomes turbulent is critical to improving efficiency and/or longevity of equipment in turbomachinery, aerospace, marine and many other industries. The Menter–Langtry γ–θ laminar–turbulent transition model™ gives users a powerful tool to capture various types of transition mechanisms in CFD simulation.
In addition, ANSYS CFX provides a number of scale-resolving turbulence models, such as large- and detached-eddy simulation (LES and DES) models. The development of the novel scale-adaptive simulation (SAS) model is a highlight. This model provides a steady solution in stable flow regions while resolving turbulence in transient instabilities, such as massive separation zones without an explicit grid or time-step dependency. The SAS model has shown excellent results on numerous validation cases. It provides a good option for applications in which resolution of turbulence is required.
Optimizing heat transfer can be critical in many types of industrial equipment, like turbine blades, engine blocks and combustors, as well as in the design of buildings and structures. In such applications, an accurate prediction of convective heat transfer is essential. In many of these cases, the diffusion of heat in solids and/or heat transfer by radiation also plays an important role.
ANSYS CFX software features the latest technology for combining fluid dynamics solutions using conjugate heat transfer (CHT) for the calculation of thermal conduction through solid materials. The solid domain meshes for CHT regions can be created independently, and then general grid interfaces (GGI) used to attach any non-conformal meshes that are created. Additional related features include the ability to account for heat conduction through thin baffles, thermal resistance at contact areas between solids and through coatings on solid surfaces, and advection in CHT solids due to motion.
ANSYS CFX incorporates a wealth of models to capture all types of radiative heat exchange in and between fluids and solids — from fully and semi-transparent to radiation, or opaque. The most flexible model is the Monte Carlo model that simulates the physical interactions between photons and their environment by tracing a representative number of rays through the simulation domain. It can simulate any variation from optically thick to thin (or transparent) media, both in fluids and solids. To maximize efficiency, the radiation mesh can be automatically coarsened in regions in which changes in the radiation field are small.
ANSYS CFX gives your the choice of different spectral models to account for wavelength dependencies in a simulation. It also enables scattering effects to be taken into account.
Numerous CFD applications involve not just a single fluid phase but, rather, multiple phases. ANSYS CFX is a leader in multiphase modeling technology. Its varied capabilities allow engineers to gain insight into equipment that is often difficult to probe. A complete suite of models allows ANSYS CFX to capture the interplay between multiple fluid phases like gases and liquids, dispersed particles and droplets, and free surfaces. All of these models benefit strongly from the coupled solver technology to achieve robust and scalable multiphase flow solutions.
The free surface flow option in ANSYS CFX allows the simulations of open channel flow, flow around ship hulls, tank filling and sloshing, Pelton turbines, and many other situations. A special compressive discretization scheme is used to maintain a sharp interface at the free surface. Optionally, users can have two distinct velocity fields, to allow for separation to be simulated in conjunction with strong mixing or entrainment.
The Lagrangian particle transport model users to simulate disperse phases discretely distributed in a continuous phase, such as liquid sprays or airborne solid particles. The functionality is extended by a large number of additional models for phenomena such as primary and secondary spray break-up, particle-wall interaction, wall erosion due to particle impact, particle-particle collision, and coal combustion.
The Eulerian multiphase model features a wealth of options to capture the exchange of mass, momentum and energy. This includes numerous drag and non-drag force models as well as robust models for phase change due to cavitation, evaporation, condensation and boiling. Additionally, the multiple size group (MUSIG™) model allows the simulation of the effect of turbulent breakup and coalescence of different bubble sizes.
For disperse phases that equilibrate quickly with their surroundings, such as small bubbles or particles rising in tundishes or settling under gravity in clarifiers, the Algebraic Slip Model is a very efficient option available in ANSYS CFX.
Whether simulating combustion design in gas turbines, automotive engines, or coal-fired furnaces or assessing fire safety in and around buildings and other structures, ANSYS CFX software provides a rich framework to model chemical reactions and combustion associated with fluid flow.
There is a complete range of options for all situations: a rich library of predefined chemical reactions that can be easily edited and extended by users as well as the integration of ANSYS reactive integrated flamelet (RIF) for detailed chemistry tables. These are rounded out with models for auto and spark ignition, pollutant formation (NOx, soot), residual exhaust gases, knock, wall quenching, flame extinction and more.
The eddy-dissipation model (EDM) and finite-rate chemistry (FRC) models are provided in ANSYS CFX software for relatively fast and slow reactions, respectively, when compared to the mixing of reactants due to turbulent fluid flow. Simulations are not limited, however, to either extreme, as the two models can be combined, with the reaction rate being taken as the minimum of the two, both for single and multi-step reactions, from pre-defined or user-defined reactions.
In situations in which fuel and oxidant are fed into a system separately and the chemistry is assumed to be relatively fast, the laminar flamelet model with presumed probability density function (PDF) offers a practical and efficient means to depict the detailed chemistry of hundreds of species without having to solve hundreds of transport equations.
The burning velocity model (BVM) is well suited for combustion in which oxidant and fuel are premixed or partially premixed and the flames are steady, such as in gas turbines. BVM is coupled with the laminar flamelet PDF model to model post-flame front mixing and reaction.
Like the BVM model, the extended coherent flamelet model (ECFM) is suited for premixed or partially premixed fuel/oxidant combinations. It can capture post-flame front mixing using the laminar flamelet PDF model. However, an additional degree of freedom makes it more suitable for unsteady flames and moving geometries, as found for example in internal combustion engines. It includes an option to incorporate the quenching effect walls can have on flames.
Courtesy German Aerospace Center (DLR), Institute of Combustion Technology.
ANSYS CFX is a leading CFD code in this demanding industry, in which the requirements in terms of accuracy, robustness and speed are among the highest. Over two decades of experience in rotating machinery simulation has ensured that ANSYS CFX software provides all the models and infrastructure for accurate, robust and efficient modeling of all types of pumps, fans, compressors, and gas and hydraulic turbines.
ANSYS provides a wide range of products for turbomachinery design and analysis, including rapid optimization of preliminary designs based on 2-D through-flow analysis using the ANSYS Vista TF tool as well as the turbomachinery-specific geometry and mesh-generation tools ANSYS BladeModeler and ANSYS TurboGrid. In addition, tight connection to ANSYS structural mechanics solutions allow fluid–structure interaction (FSI) to be captured whenever required.
Within ANSYS CFX, tailored pre- and post-processing tools complement a full suite of interface models to capture the interaction between rotating and stationary components.
The transient rotor–stator capability resolves the true transient interaction between components for maximum accuracy. It can be applied to individual pairs of blade passages or to the entire 360-degree machine. Setup and use is as simple as it is with the other frame-change models, and it is possible to combine transient and steady-state frame change interfaces in the same computation. Complementing this is the inclusion of second-order time differencing, which delivers greater transient accuracy. Furthermore, transient blade row (time and Fourier transformation) models allow for the simulation of multi-rows, unequal pitch systems using only a few blade passages and less that the full 360-degree geometry.
The stage interface model is a simpler model that provides faster solutions than the full transient rotor-stator model. It enables a steady-state computation to be used by performing circumferential averaging of the variables at the interface.
Various options are available to accurately capture transient interaction between rotating and stationary components. This includes a selection of transient blade row interaction models for modeling the interaction between components in which the number of blades is unequal and, therefore, the pitch-wise extent of the geometrically periodic blade passages is also unequal. This powerful set of models allows significantly faster solution times with reduced-memory requirement compared to transient simulations of the full blade rows.
Another way to model the interaction of rotating and stationary parts is with ANSYS CFX software's frozen-rotor model, which is useful when the circumferential flow variation that each blade passage experiences is large during a full revolution. With this option, computations are performed in a steady-state mode, based on the assumption of quasi-steady flow around the rotating component at every rotation angle. The additional rotational effects (Coriolis and centrifugal terms) are included in the rotating regions, and the frame change across the sliding interface is accommodated automatically when linking the different regions of the solution.
The effect of solid motion on fluid flow can be modeled by coupling ANSYS CFX software with ANSYS structural mechanics solutions. Using the unified user environment (ANSYS Workbench) fluid–-structure interaction (FSI) simulations can be easily set up. ANSYS CFX FSI solutions are an industry leader in robustness, applicability and accuracy for two-way FSI. There is no necessity to purchase, administer or configure third-party coupling and pre- and post-processing software.
The robust and flexible algorithm to deform a given fluid volume mesh in ANSYS CFX tolerates even very large boundary displacements. These displacements may be defined explicitly by the user (for example, by using CEL) or be the implicit result of an FSI simulation with ANSYS structural mechanics software or from the rigid body solver within ANSYS CFX. In all cases, boundary displacements are diffused into the interior volume mesh while ensuring that small or near-wall elements are deformed less. This maintains good boundary layer resolution and allows for larger mesh deformations with a single mesh topology.
In situations in which the boundary motion is more extreme and a single-mesh topology is simply insufficient to model the entire displacement, ANSYS CFX provides options for automatic remeshing when required during a simulation. The automatic remeshing allows users to connect to ANSYS ICEM CFD software, exploiting its scripted, batch-meshing capabilities to drive the automatic remeshing from within ANSYS CFX. Alternatively, users can integrate any other scriptable meshing software.
The immersed solids method is an additional FSI option within ANSYS CFX that allows simulation of unlimited motion of solid objects through fluid regions, as it avoids any mesh deformation or remeshing. As an immersed solid passes through a fluid, the region of overlap is determined and the fluid solution is adjusted to reflect the presence of the solid by applying appropriate source terms. The solid motion can be defined by the user with complete flexibility, or it can be an implicit result from the rigid body solver within ANSYS CFX.
A fully integrated and implicit six-degree-of-freedom rigid body solver in ANSYS CFX permits boundary, domain, or subdomain motion to be an implicit result of the forces and moments acting on a rigid body of a given mass and defined moments of inertia. Applications include store separation from aircraft and ship motion under the influence of waves.
ANSYS CFX delivers powerful and scalable high-performance computing (HPC) options. Parallel processing with ANSYS CFD HPC allows users to consider higher-fidelity CFD models — including large systems with greater geometric detail, (for example, a full 360-degree blade passage rather than a single-blade one) and more complex physics (such as unsteady turbulence rather than a steady turbulence model). The result is enhanced insight into product performance — insight that can’t be gained any other way. This detailed understanding can yield enormous business benefits, revealing design issues that might lead to product failure or troubleshooting delays. Using HPC to understand detailed product behavior provides confidence in a design and helps ensure that a product will succeed in the market.
ANSYS CFD HPC increases throughput by speeding up turnaround time for individual CFD simulations. This enables consideration of multiple design ideas and provides the ability to make the right design decisions early in the design cycle. Using ANSYS CFD HPC helps make an engineering staff, and almost any product development process, more productive and efficient.
The ANSYS CFX technology incorporates optimization for the latest multi-core processors and benefits greatly from recent improvements in processor architecture, algorithms for model partitioning combined with optimized communications, and dynamic load balancing between processors. ANSYS CFD HPC is easy to use and works exceptionally well on a number of systems — from multi-core desktop workstations to high-end HPC clusters.
The detailed behavior of materials under the influence of flow conditions, such as pressure or temperature, can have a critical effect on the accuracy of CFD predictions. ANSYS CFX software provides a wide range of material modeling options to ensure nothing stands in the way of achieving the highest fidelity solutions possible.
ANSYS CFX comes with a rich database of material properties for a large range of liquids, gases, and solids. Both ideal and real fluid behavior can be modeled using well-established and advanced equations of state. Numerous relations are available for viscosity and conductivity variations, from Sutherland’s formula to models based on kinetic theory. For non-Newtonian fluids, an ample selection of viscosity models is provided to account for their shear-rate dependent behavior.
Should a simulation involve a proprietary material, or any other material or material property not already included in the material database, ANSYS CFX users can take advantage of the flexibility of the user environment and the power of the CFX expression language (CEL). CEL allows easy definition of any number of new materials or dependencies of material properties on flow conditions such as pressure, temperature, shear-strain rate and more. Users can enter any algebraic expressions for such custom models directly in the CFX-Pre GUI using the simple CEL syntax, avoiding the need to program separate external routines. It is as straight-forward as writing them down on paper.
ANSYS CFX software offers many options for customization and automation, including user-defined GUI extensions to allow advanced users to create customized input panels with application-specific terminology and explanatory sketches, a customizable model library with predefined setups for complex or frequently repeated cases, batch execution of macros and recorded session files, and full access to the Perl programming language for maximum programmability.
The CFX Expression Language (CEL) and CFX Command Language (CCL) form the foundation of the flexibility of ANSYS CFX and its user environment.
CEL is a powerful definition language that allows users to incorporate their own custom models quickly and directly in the standard ANSYS CFX user interfaces. For example, users can take advantage of CEL to add new physical models, create additional solution variables, define property relationships, and set boundary conditions and profiles. CEL syntax is intuitive and easy to learn. It includes many predefined functions and operators to allow easy customization of simulations in a number of ways.
CCL is the intuitive text-based command-file that can be used as a GUI alternative to access the solver, implement physics, define boundary conditions and set solver parameters. Parametric studies can be quickly defined by editing command files and changing the appropriate values. This enables ANSYS CFX software to be run in batch mode or to be integrated in optimization and design systems.
Furthermore, CEL and CCL functions can be combined with ANSYS Workbench (project-wide) scripting tools that go beyond fluid dynamics itself. In this respect, productivity can be significantly increased by using the scripting tools for parameter/file/data management as well as design exploration studies.
"I have always been a fan of the ANSYS CFX Expression Language (CEL), and I use it to easily customize, extend, and parameterize my simulations all the time. In Release 12.0 it is even easier and faster to access my custom expressions inside CFX-Pre , it's child's play!"
— Fabio Kasper, Development Engineer, Whirlpool
Post-processing tools for ANSYS CFX can be used to generate meaningful graphics, animations and reports that make it easy to convey fluid dynamics 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 CAE packages for additional analysis. Within the ANSYS Workbench environment, ANSYS CFX solution data can be mapped to ANSYS simulation surfaces for use as thermal or pressure loads. In standalone mode, ANSYS CFX can map structural and thermal loads on surfaces and temperatures in volumes from ANSYS CFX to third-party FEA meshes.
Geometry Defeaturing and Editing
ANSYS DesignModeler provides geometry modeling functions unique for simulation. Some features include CAD geometry modification, fluid enclosure creation, detailed geometry creation and concept model creation tools.
Six-Sigma Analysis and Design Exploration
ANSYS DesignXplorer software performs robust design analyses for any ANSYS Workbench environment simulation, including those with CAD parameters. ANSYS DesignXplorer allows users to study, quantify and graph various structural and thermal analysis responses on parts and assemblies. It incorporates both traditional and nontraditional optimization through a goal-driven optimization method.
Turbomachinery-Specific Add-On Modules
Rapid 2-D Through-Flow Analysis
ANSYS Vista TF provides rapid preliminary optimization of turbomachinery designs on the basis of 2-D through-flow analysis.
Rapid 3-D Blade Design Tool
ANSYS BladeModeler software is a specialized, easy-to-use tool for the rapid 3-D design of bladed rotating machinery components.
Turbo-Specific Meshing Tool
ANSYS TurboGrid software is an easy-to-use, highly automated meshing tool specifically designed for bladed rotating machinery.
ANSYS CFD technology is ready for use with the ANSYS Engineering Knowledge Manager (EKM). The ANSYS EKM system addresses simulation data management challenges. It assists engineers with important aspects of simulation data management, including archiving, backup, traceability, maintaining audit trails, collaboration and IP protection. These features ensure that the knowledge gained by ANSYS CFD simulations is properly captured and ready for use in the corporate engineering process.