Overview of Computational Fluid Dynamics (CFD Software)

Comprehensive Flow Excellence for Computational Fluid Dynamics.

Computational fluid dynamics (CFD) is an aspect of multiphysics system analysis that undertakes simulating the behavior of fluids and their thermodynamic properties using numerical models. In the case of Cadence’s robust CFD suite, this includes application areas such as propulsion, aerodynamics, hydrodynamics, and combustion. What makes CFD platforms pivotal is their ability to adapt to specific instances of additional physical phenomena.

Using CFD, not only will you be able to resolve the core Navier-Stokes equations that comprise the field of CFD, but also you can trust these tools to resolve issues like multiphase flows, incompressible and compressible flows, laminar flows, acoustics, particle tracking, combustion phenomenon, thermal exchangers, diffusion, smoke propagation, and many more. Our suite of CFD tools have been around for decades, specializing and evolving along with the industry.

Cadence is committed to advancing system innovation through our core competency in computational software. Our computational fluid dynamics solutions are a key part of fulfilling that commitment. With an industry-leading meshing approach, and a robust host of solver and post-processing capabilities to pair alongside, you’ll be thinking of computational fluid dynamics as “Cadence fluid dynamics” in no time.

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Customizable Solutions for your Workflow

To solve complex flow equations, highly accurate meshing and geometries are needed to provide input for efficient numerical methods. Our exceptional CFD simulation software provides CFD meshing, solving, and post-processing, and is compatible with external CFD workflows. The computational world is due for an update to computational methodologies, and the update is universal product suites.

Meshing

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Meshing your geometry is the first and, potentially, the most impactful stage of your CFD workflow. Meshing impacts accuracy, convergence, and simulation process efficiency. Our robust geometry preparation capabilities shorten the time needed to create a high-quality mesh.

There are many avenues for meshing available. Our rapid generation of hybrid meshes uses an advancing layer technique to generate layers of near-wall, boundary layer resolving prisms, and hexahedra. To refine and adapt your mesh, clustering sources provide control of mesh resolution away from walls, near wakes, vortices, and other flow features.

Point cloud sources provide the opportunity to adapt the mesh to your flow solution. Honed over decades, block-structured quadrilateral and hexahedral methods provide a broad suite of elliptical and hyperbolic partial differential equation (PDE)-based methods that generate grids with smoothness, clustering, and orthogonality.

Whether your mesh is structured, unstructured, or hybrid, you can generate it for use with an overset flow solver using the built-in interfaces to overset grid assemblers. If you use a high-order flow solver, you can utilize degree elevation and mesh curving capabilities.

Solving

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After you have meshed your model, the physics of the real-world environment can be solved to your desired fidelity. Thankfully, we have access to plenty of application-specific workflows from our decades of software development to improve efficiency or fidelity. These application-specific workflows include but are not limited to propulsion, aerodynamics, acoustic, and other needs.

Capable of working through the core Navier-Stokes equations fundamental to CFD, our solvers have been optimized for specific physical phenomena. This platform experience enables engineers to streamline their workflows and switch from one physics to another with ease. Often, engineers are forced to consider speed or fidelity, but with our platform you can investigate fluids, structures, or acoustics holistically.

Post-Processing

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As the need for ease of access to real-world modeling grows, improved data visualization of CFD results enables more informed decision-making. Post-processing creates an efficient representation of large datasets generated from CFD simulations.

Unique interface and customizable palettes aside, post-processing will also need to scale with the size of larger simulation problems. Rather than waiting for a simulation to complete, Cadence offers co-processing where running simulations and monitoring solver convergence in real time can provide early insights.

Co-processing is the most efficient way to visualize intermediate results concurrently to the simulation solving. Where many large simulations require huge swathes of CPU memory, one can even render transient plots while the solver is running to greatly reduce disk space usage and data processing time.

Potential Fluid Flow Pathways in CFD

Determining what tools, equations, and models you want to use in CFD is an essential step in the overall simulation process.

Computational fluid dynamics (CFD), fluid mechanics, and representations of potential flows

A Glance At Some Applications of Our Dynamic Software

Computational fluid dynamics has long been a field where individuals create the algorithms, tools, and solutions they need in order to solve the specific problems they’re experiencing. It isn’t enough these days to think product design in individual components when there are so many readily available tools to create a unified approach.

With aerodynamics, heat transfer, and fluid flow mechanics at the core of so many unique industries these days—aerospace, energy production, and automotive to name a few—it is no surprise to see CFD continuing to rise in importance. Below, you can see where we excel in some of the more standout categories of CFD.

Aerodynamics

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Aerodynamics is a particularly common application for CFD. Calculating drag, lift, and stall angle, while including effects of turbulence, laminar-turbulent transition, and boundary layers, as well as wind tunnel conditions, is necessary. We pride ourselves on both our internal and external aerodynamics solutions.

It isn’t enough to simulate airfoil conditions these days as vehicles are being developed across subsonic, transonic, supersonic, and hypersonic environments with unique numerical elements to be solved for each. Within aerodynamics, much of what you are solving are Reynolds-Averaged Navier-Stokes (RANS) equations with additional applied computational techniques like direct numerical simulation (DNS), and large eddy simulations (LES) as considerations in the computational field of aerodynamics.

Turbomachinery

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We’ve come a long way from water wheels yet transferring energy between a rotor and a fluid is still the base mechanism behind the concept of turbomachinery. Simulating flows in turbines, compressors, fans, propulsion mechanics, compressible, and incompressible flows are all significant parts of CFD for turbomachinery.

Turbomachinery has vast applications in industries like energy production with hydroelectric or wind turbines, or marine applications with waterjet drives and steam turbines. There are really too many applications to name, but some of our additional prowess lies in turbopumps for rocket engines, turbochargers, and superchargers in engine enhancement.

Some problems that CFD attempts to resolve within turbomachinery are optimizing engine and power efficiency of compressors and turbines, including hydraulic turbines. Also, avoiding cavitation in space cryogenic pumps, predicting and reducing noise, and secondary effects due to seals and cavities, as well as many more.

Heat Transfer

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The physical phenomenon of heat flux due to temperature differences, and its interaction with the fluid flow is known as Conjugate Heat Transfer (CHT). Simply put, heat transfer analysis is looking at conduction, convection, and radiation to determine the ways in which energy is transferred. Applying heat transfer simulations and modeling in CFD models means opening an entire world of heat management possibilities.

Some of the applications here involve cooling simulations, convective heat transfer, as well as determining any potential radiation and radiative effects. You can use technology like heat exchangers to improve the efficiency of engines and other combustion phenomenon. Or you could use CHT to simulate the opposite end of the spectrum in frost and icing effects for hypothermal environments like arctic waters. Both high-temperature environments and freezing atmospheric conditions are all considerations for the vast potential of heat transfer analysis in CFD.

Aero- and Vibro-Acoustics

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Acoustics continuously gains in importance with the increase in power and noise generation in machinery. In aero- and vibro-acoustics, CFD methods like noise propagation, radiation, and fluid-structure coupling are all relevant and involved in solving processes. With the reliable and comprehensive non-linear harmonic (NLH) method, you can simultaneously calculate near-field propagation and noise source of turbomachinery tone noise.

Additionally, utilize the boundary element method (BEM) or the Ffowcs Williams and Hawkings (FW-H) method to compute noise radiation to far-field microphones. For broadband noise, you can apply either flow-noise source reconstruction, or perform direct Large Eddy Simulations (LES) to identify the main regions of noise sources.

Unique Phenomenon Require Specialized Solutions

Because fluids and fluid-structure interaction are in just about any system available, CFD simulations are at work in most industries. Some of the key industries where CFD is relevant are marine, commercial and military aerospace, automotive, biomedical, and petrochemical, as well as processing and chemical industries.

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Automotive

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External aerodynamics and turbomachinery have long been a fundamental component of the automotive industry simulation challenge. These days, aerodynamics, propulsion, and combustion, as well as thermal exchangers for engine efficiency, water particle tracking, acoustic noise modeling, and flow interactions with structural mechanics all contribute vitally to the overall health of an automotive vehicle. Having specialized solvers to tackle any of these potential issues is vital for a more comprehensive simulation profile within your automotive systems.

Looking ahead, whether jumping at the opportunity to design more electric vehicles (EV) or working to minimize acoustic noise or power disruptions, CFD continues to be pivotal. Improving current demand and capacity of powertrain systems will require refined optimization, and the electrothermal reactions within power systems will need to continue being closely monitored to improve both time between maintenance as well as power efficiency. Look through our suite of available solutions to see how they can address your CFD needs.

Aerospace

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The challenge of aerospace CFD is connected to the modeling of turbulence (and transition). The current widely used approach is based on Reynolds Averaged Navier-Stokes (RANS) models, where all properties are averaged over the turbulent fluctuations spectra. This requires the addition of turbulence models based on additional semi-empirical transport equations for relevant turbulent quantities, such as kinetic energy, dissipation, or turbulent eddy viscosity.

These models, widely used, have nevertheless many deficiencies, which can be addressed by scale-resolving simulations based on Large Eddy Simulation (LES) or Detached Eddy Simulations (DES) combining RANS and LES methodologies.

Accounting for vast changes in temperature like cold flows, simulating heat exchanger profiles, and optimizing their performance, as well as examining the micro and nano-scale materials flowing through any system can all be on the plate of a thermal aerospace engineer. In addition, working through aerodynamic efficiency, controlling acoustics, and engaging in the next inspiration for increased speeds and efficiency in travel are all vital for CFD simulations to be able to accomplish.

Health

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As health technologies advance into more careful and calculated domains of bodily control, so too does the need for advanced and accurate simulation and modeling. Where CFD takes place in the human anatomical structure is typically through its vascular structures and blood flow. Learning and replicating behaviors of blood flow using methods within CFD, such as studying fluid-structure interactions, turbulence modeling, and particle tracking, all enable a greater ability to resolve critical bodily challenges.

Thinking beyond the blood though, as pollution levels rise and airborne illnesses continue to gain in potency, utilizing CFD-based air flow techniques both internal to the body to regard lung capacity and performance as well as modeling breath externally to understand is literally vital.

Whether virtually prototyping the human body or trying to plan and simulate for a future outbreak scenario, CFD can enable health and biomedical researchers to arrive at the conclusions necessary to protect the people most vital to them.

Industrial Systems

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Industrial equipment is tried and true. But this doesn’t mean that industrial equipment isn’t due for an upgrade. Modern farms, warehouses, plants, and automated services all require more accurate, more efficient equipment to do the jobs that need doing, whether this is in the form of agricultural vehicles, heat exchangers, mixing vessels, or some new development in automation or improved efficiency.

Especially with concerns around energy efficiency and environmental issues of emission reductions, CFD simulation will maintain and grow its footprint in the industrial equipment space with the coming years.

Industrial machinery is typically overdesigned and overbuilt to avoid failure. Now industrial machinery development can utilize simulation techniques to generate more cost-effective and efficient systems. Turbines, fans, and compressors all function on common operating principles that can accurately be depicted with CFD analyses. Modeling compressible and incompressible fluids, as well as managing vibro- and aero-acoustics is vital within these demanding environments.

Our decades-long commitment to the marine environment and ship hydrodynamics has resulted in fine-tuned resistance, propulsion, sea-keeping, and maneuvering calculations. Any matrix set up to account for unique speeds, angles, sea conditions, or other domain definitions is able to be automated in our CFD environment. Additionally, fully transient hydraulic calculations are available within our solver software with offshore and marine industry-specific post-processing capabilities.

Diverse Flow Domains and Technological Potential

The wonder of technology is how quickly it evolves. This applies to both the products being designed and the software to design them. But the nature of these evolutions is that sometimes we are using our tools to experiment and answer the questions that nobody has asked yet. Keep looking forward with tomorrow’s services and needs to create the next great advancement. With CFD software maturation, you can bring CFD earlier and earlier in the product design lifecycle.

Laminar and Turbulent Flows

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Fluid flows can be either laminar or turbulent. Generally, laminar flows occur with slow moving fluids or particularly viscous fluids with parallel fluid layers with no eddies or currents to the flow. Understanding the physics of the flow is paramount for high degrees of accuracy regarding flow domains and characteristic lengths.

In CFD, laminar flows can be important depending on the system at work but also often work as model or reference flows while working in the laminar-turbulent transition ranges. By understanding the types of flow at work in a system, the Reynolds number will typically describe the global domain behavior of these flows instead of their local behaviors. The properties of aerodynamic flows are only dependent on the Reynolds number, which is a measure of the ratio of inertial force to the shearing force of the fluid, also considered as the ratio of convection over viscous diffusion.

Each flow system becomes turbulent when the Reynolds number reaches a certain threshold, turbulence being the global instability of the flow, with a chaotic, statistical behavior. This behavior can only be predicted by numerical methods through appropriate CFD methodologies.

Turbulent flows range with more levels of disturbance in the fluids or instabilities in flows. However, small Reynolds number flows, known as Stokes or creeping flows, indicate where the viscous forces overtake the inertial forces.

Venturi Effect

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While the Venturi effect is a fairly common and simple physical phenomenon in the broader scheme of CFD, it can have grand impact in the fluid flow of engines, joints, and tubing. The Venturi effect is such that within an environment with constant mechanical energy, fluid velocity when moving through a narrower or constrained area or chokepoint will increase and relative static pressure decreases for subsonic flows, whereas at supersonic flows the effect is reversed.

In more localized phenomenon, the Venturi effect can be seen within engines and turbines; however, larger structural designs like skyscraper or city buildings can also trigger the Venturi effect. The cornerstone for utilizing the Venturi effect in various systems will be the Venturi tube, which features a recognizably narrow chokepoint with wider ends that increases fluid velocity.

Air Resistance

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Air resistance is a representation of the force expressed by drag coefficients in the aerodynamics world. Effectively, air resistance, or drag, refers to opposing forces to the motion of an object moving through air. Since drag operates against the motion of the system, its force must be fought against by the system (typically through an acceleration force).

Within external aerodynamics, to use an aircraft as an example, an aircraft will move in the surrounding air causing friction between air and the aircraft. This friction is due to the shear stresses that must be simulated and modeled accurately.

Similarly, in internal flows, the shear stresses generated friction forces create a pressure drop between the inlet and the exit of the flow domain. Drag and pressure drop are an endlessly optimizable field of study within CFD that our tools are more than ready to provide answers and experimentation for.

Hypersonics

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Historically, capturing shocks with CFD has been a major achievement. Most commercial aircraft are operating at subsonic speeds with transonic flow behavior along the wing suction side, reaching Mach numbers up to 1.3 and returning to subsonic speeds through a shock wave. An omnipresent and growing interest field is the field of hypersonic equipment, weaponry, and aircraft.

Supersonic aircraft create sonic booms when breaking the sound barrier. Hypersonic speeds, considered above Mach 5, historically have been developed in the form of expensive and less efficient missile systems from as early as the 1930s and 1960s. While commercial development at hypersonic speeds is still in early development, space applications, such as the flow around a returning space shuttle, remain highly challenging for CFD.