CAE simulation, explained
Engineers can test a design in software before the first prototype exists, if the model behind the test can be trusted. This guide explains how a CAE simulation is set up, solved and checked against real tests, which analysis answers which question, and how to choose CAE software.
What is CAE simulation?
CAE (computer-aided engineering) is the use of software to predict how a product will perform: how it deforms, vibrates, heats up or moves, and how fluids flow through and around it. A CAE simulation is one such virtual test, usually built from the design’s CAD geometry and run before a physical prototype exists.
Siemens defines computer-aided engineering as “the use of computer software across industries to simulate product performance to improve designs or assist in the resolution of engineering problems”. The word “simulation” is often used as the generic term for CAE.
CAD, CAE and CAM
CAD
The geometry of the part
CAE
The same part meshed and analysed
CAM
The toolpath that makes it
| Aspect | CAD | CAE | CAM |
|---|---|---|---|
| Produces | The geometry of a part or product | A simulation model built from that geometry, and its predicted performance | Instructions (G-code) that drive CNC machine tools |
| Answers | What does it look like, and does it fit? | Will it perform as required? | How do we make it? |
| Order | First: it defines the design | Next: it tests the design virtually | Then: it makes the parts |
CAD and CAE work in a loop: the CAE model is built from the CAD geometry, and CAE results send changes back to the design, which is quicker than building and testing prototypes. Tools differ in how tightly they connect: Simcenter FLOEFD runs inside the CAD system, Simcenter 3D keeps its models in step with CAD changes, and Simcenter Femap works independently of the CAD system and the solver.
What is CAE software used for?
CAE software is used whenever engineers need to understand or predict how physics will affect a design: whether a bracket survives its loads, how hot a circuit board runs, how much pressure a valve loses, or which of many variants is lightest. It replaces or supplements experiments and analytical methods. Hand calculation still works for a beam or a straight pipe, and stays the sanity check; CAE takes over when the geometry, contacts, coupled physics or time dependence put the problem out of reach of a closed-form answer. Our Nusselt number and dimensionless numbers calculators are examples of that sanity check.
What is a CAE program?
A CAE program, also called CAE software, a CAE tool or a CAE system, packages the steps of a simulation (the CAE workflow): a pre-processor for geometry, mesh and loads, one or more solvers, and a post-processor for the results. Some combine everything in one environment, as Simcenter 3D does for structures, acoustics, dynamics, thermal and electromagnetics; others specialise, as Simcenter Femap does as a pre- and post-processor for Simcenter Nastran and other solvers. Simcenter STAR-CCM+ for flow and Simcenter Amesim for systems are other examples; every tool Volupe supports is on our Simcenter CAE software page.
Types of CAE analysis
The main types of CAE simulation are structural, thermal and modal (natural frequency) analysis, noise and vibration, fluid dynamics, electronics cooling, motion, electromagnetics, system simulation, and particle and manufacturing simulation, plus design exploration and AI models that build on them. Siemens groups CAE into four sub-domains: finite element analysis, computational fluid dynamics, multibody dynamics and systems simulation. The table maps each type to the Simcenter tools Volupe licenses and supports.
| Analysis | What it predicts | Method | Simcenter tools |
|---|---|---|---|
| Structural and thermal (FEA) | Stress, deformation, stiffness, natural frequencies, temperatures and fatigue life of parts and assemblies | Finite element method (SimSolid: without a conventional mesh) | Simcenter 3D with Simcenter Nastran, Simcenter Femap, Simcenter OptiStruct, Simcenter SimSolid |
| Noise, vibration and acoustics | Noise and vibration performance and sound quality | Structural dynamics and acoustic simulation | Simcenter 3D |
| Fluid flow and heat transfer (CFD) | Flow, pressure, turbulence and heat transfer in liquids and gases | Navier–Stokes equations solved on a mesh of small cells | Simcenter STAR-CCM+, Simcenter FLOEFD |
| Electronics cooling | Temperatures from IC packages and boards to enclosures and data centres | CFD | Simcenter Flotherm |
| Motion | Forces, torques, velocities and accelerations in mechanisms | Multibody dynamics | Simcenter 3D |
| Electromagnetics | Fields, forces and losses in motors, transformers, actuators and sensors | Low-frequency electromagnetic field simulation | Simcenter MAGNET |
| System simulation (1D) | How mechanical, hydraulic, thermal and electrical components work together | System models of connected components | Simcenter Amesim, Simcenter Flomaster |
| Particles (DEM) | How bulk and granular materials behave in handling equipment | Discrete element method | Simcenter EDEM |
| Manufacturing processes | How processes and manufacturing tools perform, alongside the product | Process-specific simulation | Simcenter Inspire (manufacturing simulation) |
| Design exploration and optimisation | Which design best meets several targets | Automated design studies, optimisation, topology optimisation | Simcenter HEEDS, Simcenter OptiStruct, Simcenter Inspire |
| AI models | Near-instant predictions from earlier simulation results | Machine learning surrogates and reduced order models | Simcenter PhysicsAI |
Coupled simulation
Products rarely stay inside one discipline, and modern tools couple the physics: fluid–structure interaction, thermal-mechanical simulation, flexible bodies in multibody dynamics, and electromechanical-thermal analysis.
In Siemens’ planing-hull example, Simcenter STAR-CCM+ models the vessel in waves, and the wave-impact pressures are applied to the hull’s structural model in Simcenter 3D to check its structural safety. As described, that is one-way coupling: loads pass from the flow to the structure. In two-way coupling the deformation also changes the flow, and both solvers exchange data as the solution runs.
Volupe’s Christoffer Johansson walks through an FSI set-up in How to set up an FSI simulation in Simcenter STAR-CCM+.
3D, 1D and AI-based models
A 3D CFD or FE model resolves the full field in space, and its runs are the most expensive. A system model instead shows how a change to one component affects the whole system, before the first prototype exists; Siemens calls these 1D models and couples them with 3D CAE tools. Reduced order models and AI surrogates, trained on detailed CFD, FEA or DEM results, answer in real time. They are covered in our guide to digital twin simulation.
How a CAE simulation works: the workflow
A typical CAE workflow, or procedure, has three steps between a question and a decision: pre-processing, solving and post-processing. The answer then changes the design and the loop runs again, and a test checks the model.
- Question
What must it achieve, and how accurately?
- Pre‑processing
Geometry, mesh, materials, loads and boundary conditions.
- Solving
The solver computes the physics on every element or cell.
- Post‑processing
Results compared between designs, or with tests.
- Decision
Change the design, or release it.
Change the design and run again (back to step 2, pre-processing)
Verify the numerics, validate against test data GCI calculator
Pre-processing: geometry, idealisation, mesh and physics
Much of the engineering judgement sits here. A structural model first idealises the geometry: thin sheet metal becomes shell elements on a midsurface, slender parts become beams, and the rest is meshed as solids. The connections, such as bolts, welds and contact, often decide the stiffness of an assembly.
The mesh decides both accuracy and run time. Regions where stress changes fast need a finer mesh than regions where it hardly changes. In a flow model the cells next to each wall must suit the wall treatment: fine enough to resolve the boundary layer, or sized for a wall function. Siemens’ SimRod CFD mesh uses trimmed cells in the core and 8 layers of prism cells at the walls; our y+ calculator estimates the first layer’s height.
The physics set-up carries as much weight as the mesh: material data, loads, supports and contact in a structural model; fluid properties, boundary and initial conditions in a flow model. Viktor Hultgren’s midsurface article shows the idealisation step in Femap and Simcenter 3D, and the CFD basics are in our CFD Handbook.
Solving
The solver applies a mathematical formulation of the physics to every element or cell. The type of problem decides how: a linear static case solves in one step, while nonlinear cases with contact or plasticity iterate. Steady problems converge to one state; transient ones step through time, implicitly with large time steps or explicitly with very small ones for fast events such as impacts. Residuals and monitored quantities show when a solution has converged.
Solving can take significant time and computing power, which is why tools should scale from a workstation to high-performance computing or the cloud when models, transient studies or design studies grow. Accuracy is a choice too: Siemens notes that engineers choose the level of accuracy that answers the question with the least computing effort.
Post-processing
Contour plots are where the work starts, not where it ends. The useful outputs are the numbers a decision needs:
- the stress at the critical location
- a pressure drop
- a temperature margin
Each is checked against mesh refinement, then compared across design variants or with test results.
Checking CAE results: verification and validation
Verification checks that the equations are solved correctly. Validation checks that the model behaves like the real product, by comparing it with measurements it was not tuned to. A model needs both before its results can carry a design decision.
ASME, which publishes the V&V standards for solid mechanics (V&V 10) and for CFD and heat transfer (V&V 20), defines verification as establishing “the mathematical correctness of the computational model” and validation as comparing “the simulation model results to real-world observations”.
Verification: is the model solved correctly?
Compute the same case on a series of refined meshes and time steps to estimate the numerical uncertainty, check that the solution has converged, and compare simple cases with known answers. Our GCI calculator turns a mesh refinement study into an estimate of the discretisation uncertainty.
Validation and model updating
CAD
The e-motor powertrain as designed
CAE model
Meshed for motion and acoustics
Test
The real hardware in a modal test
Natural-frequency error vs the modal test
Siemens’ SimRod e-motor shows what a test can do for a model. A CAE model of the electric powertrain was built for motion and acoustics, and the real hardware was modal-tested. The correlation showed that the model was too stiff. Design space exploration was then used to improve how the joints (bolts and contact) were represented, and the overall error in the natural frequencies fell from 58% to 3%.
Strictly, that second step is model updating, or calibration: the model was tuned to the same test it is compared with. ASME’s introduction to VVUQ lists calibration among the purposes of ordinary tests, separate from validation experiments, and calls blind predictions of a validation experiment “the most informative of predictive capability”. Siemens’ caption also does not say how many modes the error covers. So the 3% shows a good fit to this test, not yet a blind prediction.
Where CAE fits in product development
Siemens’ case is that CAE pays off most when it comes early. It calls this simulation frontloading: moving simulation earlier in development, where it can most impact design performance, reduce prototyping costs and avoid late-stage rework. Simulation that has been an expert tool for detailed design “can and should be used much earlier”, in Siemens’ words.
- Concept
System models and design studies compare architectures before the geometry is fixed.
- Design
3D analysis checks each change, in or next to the CAD system.
- Prototype and test
Tests validate the model, and the model reduces the number of prototypes.
- Operation
A validated model kept in step with the product becomes a digital twin.
From one run to a design study
A single simulation answers a single question. A design study varies parameters and runs the model many times, to map how a design responds or to find the best one. Our DOE calculator estimates how many runs a study needs, and Simcenter HEEDS automates the repetitive work of exploring and optimising the design space.
Simulation and test together
“While predictive simulation will continuously reduce the need for expensive measurements and prototyping, it will continue to require rigorous CAE methods and best practices validation through experiment.”
Siemens, Computer-aided engineering (CAE)
Virtual testing reduces the number of physical prototypes, and the tests that remain become more valuable: they validate the model. When a validated model is kept in step with one product in operation and fed with its data, it becomes a digital twin; our digital twin guide explains that step.
What does a CAE engineer do?
A CAE engineer builds, runs and checks simulation models and turns the results into design decisions. The work follows the workflow above: preparing geometry and meshes, choosing the physics and boundary conditions, judging accuracy against tests and reporting what to change. Many specialise in one discipline, such as structures, CFD or system simulation, and work closely with designers and test engineers.
At Volupe, application engineers work with Simcenter every day. In Life as an application support engineer, Robin Victor follows a question from a family ski trip into Simcenter STAR-CCM+: how much a roof box adds to a car’s drag. Our careers page has the open application and any open roles.
How to choose CAE software
Choose CAE software from your engineering goals. It has to cover the physics, workflow, accuracy and scale your team needs, and the right choice is not always the tool with the longest feature list. Volupe is a Simcenter partner, so the tools named below are Simcenter’s; the questions apply to any vendor.
- Which physics decide your design?
One discipline, or coupled ones such as flow and structure. The table above maps each to a type of analysis.
- Who will run the simulations?
Designers working in CAD need tools built for them, such as Simcenter FLOEFD, Simcenter Inspire and Simcenter SimSolid. Dedicated analysts need the depth and control of tools such as Simcenter STAR-CCM+, Simcenter 3D, Simcenter HyperMesh and Simcenter OptiStruct. Many teams have both, and that sets the mix of licences.
- Where does your geometry live?
Strong CAD–CAE integration reduces data transfer, geometry clean-up and rework. Simcenter FLOEFD runs inside NX, Solid Edge, CATIA V5 and Creo; Simcenter STAR-CCM+’s CAD client reads CAD parameters so a design study can change the geometry (see our NX CAD client article); Femap prepares finite element models independently of the CAD system.
- How much model preparation can you afford?
Meshing large assemblies takes time. Simcenter SimSolid works without geometry simplification and meshing, while Simcenter HyperMesh is built to set up simulations of large geometries and assemblies.
- Can it scale, and how is it licensed?
Look for tools that scale from a workstation to HPC or the cloud, and a licence model that fits how you work. Simcenter 3D offers value-based token licensing, the former Altair tools use Altair Units, a units-based subscription, and Simcenter X delivers multi-domain simulation as software as a service. How a Simcenter licence is priced is on our products page.
- Can you automate and repeat it?
Automated workflows, templates and built-in design exploration let one set-up serve many runs.
- Who helps you become productive?
Learning CAE takes time and practice, so documentation, training and technical support count. Volupe runs eighteen courses in seven Simcenter tools.
How to evaluate before you buy
Define three to five cases that represent your daily work, including one with test data. Weight the criteria that matter to you, such as physics coverage, set-up hours, run time, accuracy against the test, licence model and support, and have your own engineers run the cases. Volupe arranges trials of Simcenter STAR-CCM+ and Simcenter Amesim and demos of Simcenter FLOEFD and Simcenter Flotherm. Siemens offers a 30-day online trial of Simcenter FLOEFD and a 30-day trial of Simcenter 3D, each with sample files and guided tutorials.
Choosing within a discipline
Flow and heat
- Flow, heat and coupled physics, analyst-ledSimcenter STAR-CCM+
- Flow and temperature early, on the native CAD modelSimcenter FLOEFD
- Electronics, from chip to enclosureSimcenter Flotherm
Compare: STAR-CCM+ or FLOEFD? · FLOEFD or Flotherm?
Structures
- Structures, NVH, thermal and motion in one environmentSimcenter 3D
- FE models independent of CAD and solverSimcenter Femap
- Full CAD assemblies without meshingSimcenter SimSolid
- Set-up of large models and assembliesSimcenter HyperMesh
Femap or Simcenter 3D? Both use Simcenter Nastran: Femap independent of CAD, Simcenter 3D with models that follow CAD changes.
Systems
- Hydraulic, thermal, electrical and mechanical systemsSimcenter Amesim
- Pipe networks, pumps and pressure surgeSimcenter Flomaster
Compare: Amesim or Flomaster? · 1D or 3D?
Every tool is on our Simcenter CAE software page, and how buying Simcenter works explains the steps from first question to running licence. Volupe supports Simcenter users in the Nordic countries and across Europe; find your regional contact.
Not sure which tool fits your problem?
Tell us what you need to predict, and a Volupe engineer will suggest where to start.
A short history of CAE and Simcenter
- 1966
NASA contracts NASTRAN, a general-purpose structural analysis program; the first version runs in 1969.
- 1971
A commercial version, MSC/NASTRAN, appears.
- 1987
STAR-CD, a CFD code from Imperial College research, is released; STAR-CCM+ follows in 2004.
- 2016
Siemens acquires CD-adapco, three years after LMS, and launches Simcenter.
- 2025
Siemens completes the Altair acquisition; its tools join Simcenter in June 2026.
Sources and changelog
Sources
Siemens, Computer-aided engineering (CAE), Finite element analysis (FEA), Computational fluid dynamics (CFD), System simulation and FEA vs CFD.
Siemens, CAD-embedded CFD (simulation frontloading), Altair Units, Simcenter X and the Simcenter product pages linked in the text.
ASME, Introduction to verification, validation and uncertainty quantification (PDF), V&V 10 and V&V 20.
NASA, Computerized Engineering (Spinoff 1998); NAFEMS, Analysis origins: MSC and NASTRAN; Imperial College London, REF2014 impact case study.
Siemens press releases: CD-adapco (2016), Altair acquisition completed (PDF, 26 March 2025), Simcenter summer 2026 release.
Images: Siemens Simcenter image library (blended-wing-body GFEM, planing hull FSI, SimRod CFD mesh, SimRod e-motor).
Changelog
October 2026: rewritten with Siemens and published sources; the guide to choosing a CAE program, verification and validation, a worked Siemens example and a short history added; unsourced benefit lists removed.
CAE in practice: articles by Volupe engineers
All articlesFirst CFD run
a basic set-up, step by step
Simcenter FLOEFD
How to run a basic simulation in Simcenter FLOEFD
Robin Victor, Volupe · 2021
Read the article →
Buckling
set up with Simcenter Nastran
Simcenter 3D
Setting up buckling solutions in Simcenter 3D
Viktor Hultgren, Volupe · 2025
Read the article →
FSI
flow loads on a flexible part
Simcenter STAR-CCM+
How to set up an FSI simulation in Simcenter STAR-CCM+
Christoffer Johansson, Volupe · 2021
Read the article →
1D meets 3D
two solvers in one simulation
Simcenter Amesim
Co-simulation with Simcenter STAR-CCM+ and Simcenter Amesim
Fabian Hasselby, Volupe · 2023
Read the article →
Multi-objective
HEEDS with an Amesim model
Simcenter HEEDS
Multi-objective optimisation with Simcenter HEEDS and Simcenter Amesim
Fabian Hasselby, Volupe · 2022
Read the article →
Mesh resolution
and heat transfer accuracy
Simcenter FLOEFD
High mesh resolution for heat transfer in Simcenter FLOEFD
Christoffer Johansson, Volupe · 2021
Read the article →
Questions about CAE simulation
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What does CAE stand for?
Computer-aided engineering: the use of software to simulate how a product performs, to improve the design or solve an engineering problem. The word “simulation” is often used for the same thing; in Swedish it is CAE-simulering.
What is a CAE program?
Software for CAE: a pre-processor for geometry, mesh and loads, one or more solvers, and a post-processor for the results. Some programs combine them in one environment, such as Simcenter 3D; others specialise, such as Simcenter Femap for pre- and post-processing.
What is the difference between CAD and CAE?
CAD defines the geometry of a part or product. CAE is the next step: it builds a simulation model from that geometry to check whether the design will perform as required, before a prototype is built.
What is the difference between CAE, FEA and CFD?
CAE is the umbrella term. FEA predicts how solid structures respond to loads, vibration, heat and pressure; CFD simulates the flow, pressure, turbulence and heat transfer of liquids and gases. Both are types of CAE analysis; the CFD basics are in our handbook.
Can CAE simulation replace physical testing?
It reduces the number of prototypes and tests, but models still need validation through experiment. In Siemens’ e-motor example, test data showed that the first model was too stiff.
Is CAE only for large companies with simulation specialists?
No. Siemens argues that simulation belongs early in design, not only with experts, and some tools are built for designers: Simcenter FLOEFD runs inside the CAD system, and Simcenter Inspire brings simulation into a CAD-like environment. Learning still takes time and practice, which training shortens.
What are the main challenges when starting with CAE?
Choosing the right physics and boundary conditions, preparing geometry and meshes, and knowing how far to trust the results, which means checking them against tests. Learning CAE takes time and practice; integrated CAD–CAE tools and training shorten the start. How to choose CAE software lists the questions to ask.
Can I try Simcenter before buying?
Yes. Volupe arranges trials of Simcenter STAR-CCM+ and Simcenter Amesim and demos of Simcenter FLOEFD and Simcenter Flotherm. Siemens offers a 30-day online trial of Simcenter FLOEFD and a 30-day trial of Simcenter 3D. Ask us for a trial.
Do I need a powerful computer for CAE?
Not always. Many models run on an engineering workstation; large models, transient studies and design studies need more, so choose tools that scale from a workstation to HPC or the cloud.
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