How computational fluid dynamics lets us see the wind

Not all materials that engineers work with are tangible like concrete and steel are. We must understand and design for factors that are invisible to the eye, yet have a major impact on humans and the wider environment. For example, wind, the way temperature changes through the seasons, or how fresh air moves into and through a building.

One of ways we understand and design for these things is using Computational Fluid Dynamics (CFD), a modelling approach that has evolved into an indispensable tool in many industrial sectors and academic research.

While initially it was only used in high-technology engineering, including aeronautics and astronautics, now it has become a widely adopted methodology for solving complex problems in building engineering practice. For instance, it assists with design solutions to manage the output of exhaust stacks from laboratories. Improved technology and ever-increasing performance of processors have in fact enabled us to solve problems that in the past required a power of a big computational cluster, on an upgraded version of the desktop PC.

This paradigm shift in technological capabilities is also helpful when addressing global concerns such as climate change, a growing population, and the need to reduce development and retrofitting costs. Although CFD plays an important role when addressing all those issues, it is especially important when considering the development of clean and renewable energy technologies, meeting strict regulatory requirements for emissions control, and environmental pollution reduction.

Defining Computational Fluid Dynamics

So, what exactly is Computational Fluid Dynamics or CFD for short? At its core, CFD is a fusion of three distinct disciplines: fluid mechanics, mathematics, and computer science.

Fluid mechanics incorporate the study of moving liquids, gases and other substances that have the ability to deform. It looks at how fluid flow behaviour influences various processes, including heat transfer and chemical reactions. This is why the term ‘fluid dynamics’ is integral to CFD's description.

The physical characteristics of fluid motion can be expressed through a set of governing equations that in nature are mathematical. These equations are numerically solvable with a process involving a set of repeatable computational operations, conducted on small elements (mesh) that constitute the volume or area in which the tracked movement of the fluid occurs. Therefore, the ‘computational’ aspect involves the study of fluid flow through numerical simulations executed on high-speed digital computers.

Advantages of computational fluid dynamics

CFD offers cost-effective means of simulating real fluid flows and it is significantly cheaper compared to experimental methods. Furthermore, CFD can simulate flow conditions that are impractical to replicate experimentally, such as large-scale air flows through a specific building, including a data centre or ahigh rise building with natural ventilation.

Another key advantage of CFD is its ability to provide detailed, visualised, and comprehensive information, surpassing the capabilities of experimental methods. In other words, it shows us what is generally not visible. For example, air velocities in combination with air’s transport paths and related drops in pressure. This new perspective provides a real advantage when designing building systems and helps us to understand causes of specific issues – drafts or weak ventilation spots that can be physically noticed as regions of increased humidity or mould growth. It's important to note that CFD is not meant to replace experimental testing; it is intended to complement these methods when dealing with fluid mechanics problems. This being said, it is worth noting that the CFD simulations can and often are used to support successful test campaigns. At the early stages of problem solving, it may help to define the optimal location for the instrumentation and then later it can support the interpretation of experimental results.

Ultimately, through CFD, engineers gain a deeper understanding of how system components are expected to perform, allowing for necessary design improvements and optimisation studies.

CFD has grown into a powerful tool that offers an efficient approach to solving complex fluid dynamics' problems in various engineering disciplines. Its ability to simulate and visualise fluid flows has made it a crucial component in designing and optimising products, systems and processes, paving the way for sustainable and innovative engineering solutions. As we continue to confront global challenges, CFD will undoubtedly play an increasingly vital role in shaping the future of engineering and design.

Keep an eye out for future blogs where we will highlight how CFD has been used to tackle and solve challenges.