Whether you're new to CFD or just love reading about it, our essential guide to CFD is packed with useful content, articles and insights to get you started with simulation or provide insight into the industries and applications for which it proves so useful. Read along, email it to yourself for later, or jump to the section that interests you most.
WHAT IS CFD SIMULATION?
Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses mathematics, physics and computational software to visualise, analyse, predict and solve problems involving fluid flows. CFD analysis involves the examination and analysis of such fluid flows, in accordance with physical properties including velocity, pressure, temperature and density.
What It Means.
Put simply, computational fluid dynamics is used to simulate the movement and flow of liquids and gases, as well as the associated heat and mass transfer process. Understanding air movement and its effects on temperature distribution, as well as the dispersion and mixing of gases, smoke and contaminants is extremely important in a number of situations and industries.
An example of a CFD simulation for HVAC purposes, in an operating room
Incorporating CFD simulation into the design process allows a complex design to be tested as a computer model before construction has even begun. This has huge advantages in terms of safety, costs and timescale. In brief, modern CFD simulation tools are enabling users to solve day-to-day problems with high performance computing, made more accessible and affordable by vendors like Envenio.
A timeline showing the use of CFD by Boeing in aircraft design and development.
What Questions Can Be Answered Using CFD?
Computational fluid dynamics can answer many questions, and you'll find out more about its use in specific industries later in this article.
What if a fire broke out in the lobby? CFD allows the movement of fire and smoke to be simulated allowing smoke management and evacuation strategies to be implemented.
Is my HVAC system adequate and will it provide desirable and acceptable conditions? Whether in industrial or agricultural buildings, CFD can be used to assess the removal of heat or fumes and indicate whether the initial design criteria are being met. This is particularly useful in the indoor farming sector, influencing yields and production quality.
What are the detailed temperature distributions and how will this effect occupant comfort and equipment operation? By simulating internal spaces in buildings, an in-depth understanding can be acquired relating to the distribution of temperature, solar radiation and airflows.
How will supply air be circulated and re-circulated through a particular space? Both mechanical and natural ventilation systems can be effectively simulated to demonstrate heat transfer and air flow, helping to aid decisions around window ventilation and mechanical design.
How will a new building impact the local micro-climate? Simulation can provide insight into the behavior of wind flows around a new high-rise building, predicting the impact a structure may have on the local environment.
What Does A Typical CFD Simulation Process Look Like?
Pre-Processing: Before starting out on an analysis, it's important to define the goals of what you're looking to achieve. It's helpful to note down requirements like objectives, modelling options, boundary conditions, and the required accuracy of results. Once enough information is available, the geometrical model based on assumptions and simplifications can be decided. CAD models can then be generated by the in-built geometry builder of a CFD package or developed separately through CAD modeling software and later imported.
Next, it's time to create a mesh. Meshing is one of the most important aspects of any CFD simulation and involves the CAD model being transformed into small elements. The mesh should be precise enough to consider the complexity in geometry and flow. Regions with high gradients are identified and the mesh refined accordingly at this stage. The available computer memory must be able to handle finer meshes (the cloud has played a key role in facilitating this at a much more reasonable cost during recent years).
WHAT IS A CFD MESH?
The subdomains are often called elements or cells, and the collection of all elements or cells is called a mesh or grid. The origin of the term mesh (or grid) goes back to early days of CFD when most analyses were 2D in nature. For 2D analyses, a domain split into elements resembles a wire mesh, hence the name.
Example of a mesh
Solver: Once the problem physics are identified, fluid material properties, flow physics model, and boundary conditions are set to solve using a computer. It is also required to select appropriate physical models (turbulence, multiphase, species transport, combustion or aerodynamic) based on the problem being defined. The simulation is then carried out. While the computing is in process, the iterations should be monitored to assess the solution. The solution is said to be 'converged' when negligible variation is seen in the variables after several iterations. Monitoring the solutions can help to determine accuracy of the physical models, meshing and problem setup.
Post-Processing: The next step is to analyze the results with different methods like contour plots, vector plot, streamlines, data curve etc. for appropriate graphical representations and report. Extracting useful data from the results will enable you to make informed decisions about a design change and hopefully meet the intended objectives. With visualisation and numerical reporting tools, the flow pattern, separation phenomenon, forces, heat transfer co-efficients and flux quantities can all be identified.
If the results obtained are deemed inaccurate, the analysis should be performed again, changing the physical models and re-defining the meshing and boundary conditions.
Find out more about the stages of a typical CFD simulation.
An overview of a typical CFD simulation process
Want to learn more about CFD and using EXN/Aero? Schedule a free demo today:
WHY USE CFD SIMULATION?
In many industries, the use of real-world or wind tunnel tests is expensive, impractical, sometimes unsafe, and time-consuming. Creating a new model every time a design change is implemented adds costs and time to the overall process, potentially prohibiting time-to-market and affecting bottom line. CFD allows you to virtually simulate and test design changes, dramatically cutting the number of physical prototypes. CFD also allows you to observe the flow properties at locations which may not be accessible or could prove harmful, such as inside a combustion chamber, or between turbine blades. While simulation won't completely eradicate physical tests, it can certainly reduce them significantly.
(2) To Create Better Designs
CFD can be used as a qualitative tool for discarding (or narrowing down the choices between) various designs. Designers and analysts can study prototypes numerically, and then test by experimentation only those which show promise. In some industries, as highlighted in the previous point, designing a product, building or system can be difficult or dangerous, so designing with simulation is a more effective and safer solution. It is perhaps for this reason, that CFD proves so effective in the built environment, and why innovators like JUUL Labs are using CFD to improve the design of their vape products.
We recently assessed the results of an Aberdeen Group report on the topic, assessing the ROI of concurrent design with CFD.
The use of CFD during the design process enables a production line to be more efficient, create better products and even out-perform competitors. The Aberdeen Group report highlights the biggest impacts where CFD was not used during the process.
The advantages of simulation in the design process are showcased further in this traditional vs virtual methods in manufacturing comparison.
(3) To Improve Existing Designs
Even after a product or structure has been built, simulation has plenty of advantages. You may wish to improve an existing HVAC system in a building, test aerodynamic performance, improve thermal comfort and satisfy legislation, or test fire and safety systems. More affordable simulation using tools like EXN/Aero means validation tests can be carried out accurately and cost-effectively, enabling you to identify the malfunction and potential improvements quickly.
CFD simulation used in the development of a sports safety helmet
(4) To Remain Safe, Compliant & Energy Efficient
Whether concerning the thermal comfort of staff in an office environment or the safety of tower block residents in the event of fire, simulation helps a number of industries to remain compliant with current legislation. Being able to simulate various scenarios and behaviors is often the safest and most practical way of validating a design.
Energy Efficiency & LEED
CFD simulation can help to better optimize HVAC systems within a building, improving energy efficiency and helping to achieve compliance with certification standards such as LEED or BREEAM. The World Green Building Council has led the way in the implementation of the Advancing Net Zero project (project steering committee), reflecting its goal of supporting market transformation towards 100% net zero carbon buildings by 2050. Simulation tools are likely to play an increasing role in this strategy during the coming years.
CFD simulations are regularly used in the design and optimisation of sustainable and energy-efficient buildings
Fire & Building Safety
Fire modelling can be used to demonstrate that a proposed building design (or retrofit of an existing building) achieves a commensurate level of safety in accordance with the building and fire regulations of that particular country. CFD tools like EXN/Aero can play a key role in helping fire safety engineers to predict fire and smoke behaviour in a particular building and assess the thermal response and analyze structural behaviours. This is beneficial not only due to the near impossibility of conducting realistic experiments on complete fire safety systems in a building, but also to provide a greater level of confidence in evacuation and smoke management systems.
(5) To Grow Your Business & Keep Up With Competition
Whether you're an engineer, architect, building designer, manufacturer or consultant, you face a constant challenge to meet deadlines, exceed client expectations, manage cashflow and stay ahead of the competition. Engineering consultants require a dynamic, fluid approach to their IT requirements, with a range of factors influencing their individual needs at any one time. Changing factors may include:
- Sudden or urgent simulation projects
- An aspiration to bid on larger or more complex projects
- More simulation iterations
- Reduced compute budget or compute resources
- Restriction on compute hardware purchases
- Requirement to deliver simulations in less time
The cloud has enabled more flexible CFD simulation options to become available, helping businesses to adapt to the above factors and remain competitive. As a result, the use of simulation during the pitch process can increase your chances of winning new business or securing investment in a project. We explored how cloud CFD resources can help you to grow your consultancy business.
(5) To Cut Capital & Operational Costs
Using simulation can play a key role in cutting both capital and operational expenditure. For example, when used in the HVAC sector, simulation using EXN/Aero can help to create more energy efficient buildings through in-depth analysis and optimization of HVAC systems. This results in a reduction in operating costs (reducing energy bills) and means equipment purchases and upgrades are only carried out when absolutely necessary. Effective simulation also means existing equipment and systems can be tested to determine their appropriate operational levels, reducing chances of equipment fatigue and need for repair.
Want to learn more about CFD and using EXN/Aero? Schedule a free demo today:
COMMON AREAS OF APPLICATION
Simulation is particularly useful for addressing internal environmental challenges including thermal comfort, age-of-air testing, comfort and safety of occupants, placements of ducts, intakes and returns. Common areas of indoor application include:
- General office & room simulations
- Fire and smoke management
- Computer cluster rooms
- Contaminant control in the cleanroom & Cleanroom HVAC
- General heating, ventilation & air conditioning system optimization
- Enclosed vehicular buildings & aircraft hangars
- Swimming pool ventilation
- Indoor agricultural facilities, livestock sheds & medicinal cannabis grow rooms
- Ovens, kilns and dryers
- Boilers and heat exchangers
CFD simulation is being used widely in the indoor farming environment
CFD simulation also plays a key role outside of the internal environment and has a well documented role in the aerodynamics and automotive sectors. In addition, it can greatly contribute to the understanding of newly built structures. Common external uses include:
- Complementary role to Building Information Modelling (BIM) for Sustainable Building Design
- Wind loading & a building's impact on the local environment
- Aerodynamic testing of planes and vehicles
- Aerodynamic improvement of sports equipment
- Agricultural equipment analysis
- Tidal energy & turbines
- Solar loading & renewable energy capture
- Energy efficiency
- Smoke paths & external contaminant migration
- Rotating machinery (pumps, fans, compressors)
- Mixing tanks and chambers
- Batch and stirred chemical reactors
- Spraying and coating equipment
More information on the various industries taking advantage of CFD simulation can be seen below:
Widely championed by Boeing, CFD analysis has been an integral part of aerospace and aeronautical operations for decades.
- Design of commercial aircraft.
- Aircraft performance including fuel economy and noise.
- Speed and manoeuvrability of military aircraft and weapons.
- Reducing expensive and impractical wind tunnel tests.
Simulation plays a key role in the defense sector, helping to better understand and improve the performance of equipment and machinery.
- Understanding the aerodynamics of aircraft, missiles and submarines.
- Reducing the risk of late-stage equipment failures.
- Help decrease physical testing and reduce overall costs.
Automotive manufacturers are tasked with designing cars that satisfy visual preferences as well as meeting functional needs. TESLA's use of CFD is testament to its success within this sector.
- Improving vehicle functionality and fuel efficiency through aerodynamic design.
- Assisting the design process, presenting vehicles to market within time and budget constraints.
The performance of heating, ventilation and air conditioning systems is vital not only for the thermal comfort of occupants, but also health and safety.
- Predicting fire and smoke, and validating fire or smoke control systems.
- Creating ideal and consistent thermal conditions for occupants.
- Controlling pollutant dispersion and the removal of contaminants.
Hydropower, wind power, solar energy and oil & gas, all benefit from the use of simulation to assist the design process and assess performance.
- Use in the tidal energy sector and challenging sites.
- Reducing physical tests which can prove dangerous, impractical and expensive.
- Predicts loads on blades, wake turbulence intensity, or interference effects in wind farms
It is imperative that hospitals and research facilities carry out their work in a safe, clean environment. The use of simulation has increased substantially, to help meet the needs of this challenging environment.
- Predicting airflow and performance of HVAC systems.
- Controlling contamination in the cleanroom.
- Protecting patient and surgeon health and safety.
More and more farmers are turning to agricultural technology, simulating buildings and their HVAC systems to create the perfect environment.
- Creating and maintaining thermal comfort for livestock and human occupants.
- Predicting and controlling contaminants and pollution.
- Medicinal cannabis grow room simulations.
Simulation continues to bridge the gap between architecture and engineering, and helps designers in their efforts to sustainable building design & energy efficiency.
- Predicting wind flow around a proposed or existing building and assessing impact on a micro-climate.
- Optimising the design of a building before it is built & increasing occupant safety.
- Increasing energy performance.
Case: Operating Room (HVAC)
Controlling contamination in the hospital operating room environment is vital for the safety of patients and hospital personnel, and in this article we assess how CFD is helping to better analyze sensitive rooms and optimize HVAC systems. We highlight a recent case study where EXN/Aero helped Faure QEI to do just that, through our popular Onboarding Program.
GETTING STARTED WITH CFD
While one can find the cost of almost anything online these days, the cost of CFD seems almost secretive. Commercial software packages offered by a host of well known providers have a 'price on application' approach, putting off many SMEs who fear that 'having to ask' means 'cannot afford'. In truth, many SMEs have not been able to afford the eye-watering costs associated with such packages.
Looking back to the nineties, CFD was largely used by large aerospace and automotive enterprises who could justify expensive multi-processor machines with equally costly multi-processor CFD licenses. Moore's Law has allowed for affordable CFD-capable laptops with 8 cores, although an equivalent reduction in per-process CFD pricing has not been forthcoming - hence creating something of a barrier for SMEs and freelance engineers. This increasing deficit means users were being asked to pay high nineties prices (inflation-adjusted) to run CFD software in parallel on relatively standard multi-core computers. While some large CFD vendors now claim to offer unlimited parallel processes as an alternative to per-process pricing, their pricing structure remains hugely inflated and largely unacceptable to smaller companies.
Our own straightforward pricing page is an example of how vendors like Envenio have created affordable, accessible, high-performance software solutions available on-demand in a pay-as-you-go format. This allows CFD costs to be seen as an operating cost rather than capital expenditure, and means you can use high performance CFD tools on the fly, paying only for what you need.
You may choose to use an external consultant to assist with your simulations, or look at engaging the use of engineering services such as our Discovery Project or Onboarding Program, particularly if you have no prior experience.
Ready to get started? Schedule a demo of EXN/Aero with one of our engineers today:
How Long Does CFD Simulation Take?
Time is of the essence for almost all industries, with businesses working hard to meet deadlines, satisfy client needs and keep up with the competition. In industries such as the built environment, there's lots of iterating involved and building designs change on a daily or even hourly basis. Multiple-day simulations are of no use and our EXN/Aero platform uses GPUs to finish simulations in hours instead of days. Faster simulation turnaround times mean you can react to ever-changing requests and iterate quicker on designs.
What Equipment Do I Need?
Traditionally, one or more high-end workstations were required alongside the hugely expensive software license. Today, using a tool such as EXN/Aero, you'll be able to run simulation using only a browser, activating high performance super-computing resources on the fly, and without the eye-wateringly expensive workstation.
Do I Need Special Training To Use CFD software?
The terminology around CFD has often created a barrier around its use. How do you choose the right turbulence model? Should you be using structured grids? It can be quite difficult knowing where to start, and democratisation has been one of the big topics in the simulation world over recent years.
The CFD codes of previous decades have required the user to have a complex, in-depth understanding of the computational aspects of fluid dynamics in order to obtain accurate and satisfactory results. Today, this is not the case. A new generation of CFD software has addressed many of the barriers that prohibited the wider use of simulation, including knowledge gaps and perceptions. Codes like EXN/Aero have eliminated the need for users to understanding the computational element of CFD and instead focus on the fluid dynamics elements of a product, which of course a user should understand and master.
Envenio believes that CFD tools should complement the work of users rather than adding barriers. EXN/Aero is generally easy to use and a range of training and support options are provided. For those with no prior experience, the Onboarding Program is a particularly useful way of learning how to use the platform during a live project, where Envenio engineers provide training along the way.
CFD simulation has huge benefits for those working to improve thermal comfort of occupants in buildings
In-House vs CFD Consultancy
When looking to implement the use of CFD, you face the question of whether to bring simulation in-house or outsource to an engineering consultancy. Traditionally, one of the main reasons for outsourcing simulation were due to the perceptions and barriers facing its widespread use including time, cost and leave of expertise. With those barriers now largely lifted by modern tools, businesses are much more empowered to utilize in-house resources.
Advantages for in-house CFD include:
- In-house engineers or designers have a better understanding of the various design components, and a better knowledge of the company's end goal.
- Collected data, simulations and calculations can be saved and reused down the line adding to the capacity of the engineering department.
- Once salaries and software are accounted for, the ROI can increase with each project.
Of course, there may still be times when a business looks to outsource CFD simulation projects. This could be due to a lack of resources or expertise in-house, no time or desire to learn the software, a particularly busy workload and small team, or a one-off simulation need. Advantages of utilizing engineering services of a consultant include:
- Benefit from the advanced expertise and knowledge of a specialist.
- Engage a different perspective and fresh ideas that could prove hugely useful in a project.
- May prove more financially efficient if for a one-off requirement.
Envenio's Discovery Project is a great way cost-effectively outsource a CFD need while still staying integral in the overall direction of the project. Our engineers run the simulations for you, returning data, images and conclusions to you once complete.
What If My CFD Requirements Change?
As highlighted earlier on this page, there was a time when accessing CFD software came with inflexible licenses and large capital investment - a rather daunting proposition for SMEs. Today, vendors such as Envenio are able to offer on-demand tools on a pay-monthly basis, meaning you can access resources when needed and cancel at any time, without the long-term contract.
Traditional or Cloud-Hosted Software?
The emergence of the cloud in recent years has enabled vendors like Envenio to create on-demand solutions that bring high performance capability to a desktop computer, and react to the needs of the industry. This model brings with it the potential to offer engineers a more flexible and affordable pricing structure, and to facilitate an on-demand or pay-as-you-go structure.
Compare this to the traditional CFD codes of years gone by, where expensive leases, specialized hardware and supercomputing requirements largely prevented SMEs from being able to even consider simulation. In recent years, traditional codes required huge investment and a commitment to lengthy licenses with very little room for flexibility.
Misconceptions exist around the use of the cloud, ranging from concerns around security and safety, to reliability and queuing issues. The industry must work hard to expel such misconceptions by informing and educating engineers and those who could benefit. In addition, it must remain proactive rather than reactive to HPC trends. Many cloud-hosted services have a greater level of infrastructure than their traditional counterparts, preparing for and investing in the prevention of technical problems, thereby reducing risks and inconvenience to the user.
In the chart below, we make a time, cost and revenue comparison between traditional methods and cloud-hosted EXN/Aero.
READY TO GET STARTED?
Option 1 - Outsource your CFD simulations
Perhaps time is tight and you don't have time to use simulation tools, yet still want to experience the benefits? Our engineering services have been designed to provide the benefits of CFD simulation even when experience or resources are lacking.
With the Discovery Project, our experienced engineers will execute the project for you, working to agreed project objectives. You just tell us what you’re looking to analyze or visualize and we will prepare what you’re looking for. You'll receive all the visual data (2D, 3D images & animations) as well as full engineering data, once the project is complete. Click the button, or fill in the form below to discover the benefits.
Option 2 - Learn how to run CFD simulations with Onboarding
With the Onboarding Program, our engineers will train and support you through your first simulation setup, ensuring you get the most out of the platform, whether new to CFD or using the platform for the first time. We'll help you to mesh, set up, simulate, and post-process to achieve and evaluate the best results of an active project, so you'll still be able to exceed expectations of clients and stakeholders. Click the button, or fill in the form below to explore onboarding.
Option 3 - Schedule a FREE DEMO of EXN/Aero and get started
To find out more about how CFD could help you and your business, why not schedule a free demo with one of our engineers? The demo is a great way to see our platform in action, and to explore how it could help you and your business with HVAC simulations.