What is computational fluid dynamics (CFD)?

Computational fluid dynamics (CFD)

CFD is the use of applied Physics, Maths, and advanced computational software to visualize and interpret how a liquid or gas will flow. It predicts as well as how the gas or liquid affects objects as it flows past like impact on pressure, temperature, etc. Computational fluid dynamics is based on the Navier-Stokes equations. These equations describe how the velocity, pressure, temperature, and density of a moving fluid are related to the flow of air or gas.

CFD, Computational fluid dynamics has been around since the early 20th century and many people are familiar with it as a tool for analyzing air flow around rockets, cars, trains, and aircraft. As the cooling infrastructure of server rooms has increased in complexity, CFD has also become a very powerful tool in the data center for analyzing thermal impact and modeling airflow. CFD software requires information about the size, content, and layout of the data center. It uses this information to create a 3D mathematical model on a grid that can be rotated and viewed from different angles. CFD modeling can help an administrator identify hot spots and learn where cold air is being wasted or air is mixing.

What Are the Benefits of CFD Analysis?

CFD analysis is beneficial in product development in many ways:

#1. Efficiency

Analyzing and solving complex equations would take a huge time if done manually through conventional testing and computation. But CFD analysis software can solve complex fluid flow equations with high speed and accuracy, saving you effort and time.

#2. More Flexibility

You can measure limited quantities at a time through manual means. However, CFD analysis lets you measure all the physical quantities you want simultaneously with high resolutions due to exceptional computation power. It helps move your design quickly to physical testing and manufacturing.

#3. Practical Feedback

Engineers can create designs and test efficiency before construction with the help of CFD analysis. It allows you to change your model’s shape, structure, size, scale, etc., easily in the software and finalize the most efficient one.

#4. Real-world Experience

The simulation includes various real-world phenomena and conditions like wind motion, gravity, speed of light, etc. Hence, you can generate environmental conditions and test your designs against those conditions to understand their performance and behavior.

Now, let’s look at some of the best CFD analysis tools in the market.

Autodesk CFD

Autodesk CFD is a very good CFD simulation software for analysts and engineers to predict the flow and behavior of gases and liquids intelligently. It helps minimize the requirements for different physical prototypes to get in-depth insights into a fluid flow for design performance.

You get lots of features in this CFD software and thermal simulation tools that work with top performance. Using the tool lets you compare designs to understand the fluid behavior inside them before you move to production. Plus, you can improve pressure distribution for flow control applications and solve equations for all heat transfer models, from solid-solid or solid-fluid.

Autodesk CFD allows you to connect it to Fusion 360 to enable CAD modification and simplification. You can also use mesh automation and geometry for mesh sizing, and run multiple analyses on HPC servers, remote, or locally to solve large models with flexibility.

The software lets you optimize the design for improved building efficiency for MEP and architectural applications. You can also simulate an interface between gases and liquids, model various flow phenomena such as spilling, sloshing, and waves, and develop customized equations to get visual results.

More features you can find on Autodesk CFD are CAD connections, simulating heat sink component performance, and particle tracing to understand flow directions and circulations better. It also enables scalar mixing, radiation modeling, analyzing rotating devices, and modeling condensation and humidity.

Apart from this, analyzing solar heating loads and smoke visibility, customizable and clean user interface, data-driven results, and automation scripting via an API are also valuable features in this CFD software.

SimScale

SimScale’s CFD software is cloud-based that allows you to test, validate, optimize, and iterate your designs via online simulation. It enables all the processes in a web browser, so you don’t need to struggle with limited computational power, high costs, and accessibility.

As transient simulations need more money and time to produce accurate results, SimScale’s CFD software solves this problem. This GPU-based solver utilizes the Lattice-Boltzmann Method (LBM) to offer high accuracy and unmatched speed.

They also collaborated with Numeric Systems GmbH to create this out-of-the-box feature using Pacefish. As a result, the transient simulation times have reduced from days and weeks to minutes and hours. In addition, the software runs on several GPUs in parallel and offers 20 to 30 times shorter turnaround times than standard processes.

SimScale supports multiple turbulence modeling types like Smagorinsky, k-omega SST, Hybrid SST-IDDES, and SST-DDES. As fluid compressibility is a vital consideration, the tool supports simulations for compressible and incompressible fluids with accuracy to help you with safer and quality product design and development.

SimScale’s CFD software can solve complex fluid flow equations with precise numerical methods. Hence, it’s applicable for designing components of airplanes, airfoils, ducts, valves, and more. It also works for both turbulent and laminar flows in addition to transient and steady simulations. Therefore, it’s useful for designing pipes, smoke propagation, cleanroom, and cyclone separators.

The software offers thermal simulation capabilities, modeling multispecies or multiphase flow with the help Volume of Fluid (VoF) method. It also utilizes the OpenFOAM solver to analyze two non-mixing fluids like water and oil, useful for process engineering and marine applications.

Run steady-state simulations using multiple reference frames (MRF) or rotating boundary conditions along with transient simulations with Arbitrary Mesh Interface (AMI). You can also simulate and evaluate solid body motion involving 6 degrees of freedom (DoF), suitable for shipbuilding and pipe designs.

Ansys

Every design engineer must have used or at least heard about Ansys which offers excellent CFD simulation tools to help you make faster and better decisions. Their CFD simulations provide accurate results and high computing power and have been validated for their quality.

The CFD tools are intuitive and powerful to help you improve your product’s safety and performance while reducing development efforts and time. Besides, they ensure little to no errors and offer the great possibility to innovate and produce optimized products using industry-grade, efficient solvers.

Whether you are looking for ways to perform effective in-flight icing simulations or maximize the internal combustion (IC) engine’s efficiency, Ansys has tools to help you. They are user-friendly and advanced to save you time and help increase your productivity.

Some of the CFD products they offer are:

• Ansys is Fluent in advanced modeling with high accuracy
• Ansys CFX for outstanding speed, robustness, and accuracy in turbomachinery applications
• Ansys Chemkin-Pro is a premium CFD tool for modeling complex chemically reacting systems

Moreover, they provide other related tools, such as Ansys BladeModeler, Ansys Rocky, Ansys Vista TF, Ansys TurboGrid, Ansys Polyflow, Ansys Model Fuel Library, Ansys FENSAP-ICE, Ansys EnSight, and Ansys Forte.

OpenFOAM

Released in 2004, OpenFOAM is an open-source and free CFD software developed by OpenCFD. It has a significant user base worldwide in most science and engineering regions, including academic and commercial organizations.

OpenFOAM offers plenty of features applicable to solve simple to complex fluid flows such as chemical reactions, heat transfer, turbulence, solid mechanics, electromagnetics, and acoustics.  Furthermore, OpenFOAM’s developer community keeps on contributing to its development, and they also include customer-sponsored developments to release new versions every 6 months.

It is tested independently by ESI-OpenCFD’s app specialists, selected customers, and development partners. They perform rigorous testing on the software for quality assurance. The code evaluation process, validation, and verification include hundreds of unit tests daily.

CFD Module

Consol’s CFD modeling software – CFD Module allows you to define models and solve them to study systems with fluid flow. It also works for systems containing a combination of fluid flow and physical phenomena, meaning it works for both single and multiphase flows.

CFD Module offers tools to model the cornerstones of different fluid flow analyses, such as:

• Compressible and incompressible flows
• Turbulent and laminar flows
• Flow in free or porous media and open areas
• Thin-film flow

The software implements these capabilities via structure flow interfaces to define, analyze, and solve steady-state and transient flow problems in 3D, 2D, and 2D axisymmetric. In addition, it offers tailored functionality to solve issues concerning flow with a high Mach number, non-Newtonian flows, and rotating machinery. This is very useful in the aviation industry.

CFD Module can model reacting flows and conjugate heat transfers in the same environment to let you analyze flow problems simultaneously. Apart from this, it offers more multiphysics capabilities like fluid-structure interaction, which you can enable by combining the software with other Comsol modules.

Simcenter

Analyze and predict real-world product performance with the help of Simcenter CFD simulation software by Siemens. This industry-leading CFD analysis tool offers a fast and precise simulation of various engineering problems involving fluids, structures, and related physics.

Whether you are a designer, CFD engineer, or researcher, the software can help you analyze complex fluid flow problems and transform the insights gained into developing innovative products. It can also simulate problems involving several moving and interacting parts easily using mesh morphing, overset meshing, or a combination of the two. This software is used by various manufacturers across the globe. Even Drone companies are also using similar software for designing advanced drones.

In addition, you can use moving mesh features for steady or transient simulations and parametric studies. This provides an effortless way to replace or reposition an object and study different design configurations. Simcenter CFD software provides Lagrangian and Eulerian modeling capabilities to suit varying simulation needs accurately.

Not to mention, this is the first commercial engineering simulator that includes a DEM feature with numerical flow simulation. It helps you analyze how turbulent flows interact with reacting flows to ensure the product works fine under various operating conditions.

Moreover, you get an extensive library containing accurate models to predict aeroacoustics sources like steady-state models, DES/LES, and propagation models. You can also use battery simulations using geometrical specs and performance to validate your digital Li-ion battery design.

Flowsquare

Another free CFD software in this list is Flowsquare – a two-dimensional CFD software to analyze unsteady and non-reactive/reactive fluid flows along with subsonic or supersonic flows. It offers a handy environment for CFD analysis and aims to bring more people closer to this technology and simulate flows to feed their academic or educational interests.

Most commercial CFD tools come at high costs and need expertise and heavy computational resources, not everyone can use them, but Flowsquare is free and designed for ease of use. It doesn’t require proficiency in skills like meshing, programming CAD, and pre/post-processing. You can start by sketching a simple simulation field using any paint tool like Microsoft Paint.

Stages of CFD analysis 

CFD analysis consists of three main steps: pre-processing, processing, and post-processing – here is a brief introduction to each of them. 

1. Pre-processing 

Pre-processing is the first step in CFD simulation – which can help to define the parameters of the simulation in an accurate way if done properly. 

In this step, you will need to identify the domain of interest and divide it into several small segments – this includes preparing the geometry, meshing it, defining the properties of the materials involved, and setting the boundary layer and conditions.

Critical Elements of Pre-Processing

As mentioned above, CFD analysis is only as good as its implementer – that is, how accurately can the designer set up (or pre-process) the model – as the initial design will eventually affect the model in the later phases of analysis. 

It is crucial for the designer to ensure that the geometric model is free of errors or defects; Common issues involve:

• Gaps in the model
• Missing or overlapping faces
• Unclosed geometries like free faces, edges, and vertices

After preparation, the model should be a “closed” solid, void of any of the above-mentioned errors. Once this is completed there are several additional steps to pre-processing for your CFD analysis.

Simply by changing variables, the administrator can visualize how cold air will flow through the data center under a number of different circumstances. This knowledge can help the administrator optimize the efficiency of existing cooling infrastructure and predict the effectiveness of a particular layout of IT equipment. For example, if an administrator wanted to take one rack of hard drive storage and split the hard drives over two racks, a CFD program could simulate the change and help the administrator understand what adjustments would need to be made to deal with the additional heat load before any time or money has been spent.

2. processing

Every simulation process through a CFD program has to follow a defined set of steps. After all, simulations are a set of steps that must be complied with – as these set guidelines help to avoid getting stuck or receiving error messages in subsequent stages. 

Lastly, each of these steps is interdependent on one another, which is why proper pre-processing is so critical to being with. 

3. Post-processing

After getting results in the simulation stage, your next step is to analyze those results. Use the available methods such as vector plots, contour plots, data curves, and streamlines to achieve this. 

That way, you will get accurate reports and graphical representations. Some of the popular software tools used in the post-processing stage include EnsSight, ANSYS CFD-POST, ParaView, FieldView, and Tecplot 360.  Processes in this stage include: 

• Calculation of the derived quantities 
• Calculation of parameters 
• Visualization 
• Systematic data analysis and 
• Debugging, verification, and validation of the CFD model

The Future of CFD Analysis 

Computational fluid dynamics has found wide application in the modeling of fluid flows and has become a vital step in designing various machinery, tools, and components – such as analyzing laminar and turbulent flow through water pumps and reducing ship drag. 

As a rule of thumb, CFD does not replace real-world testing, however, it does reduce the number of experiments needed in prototyping and testing (and with that, the overall cost and risks associated). 

CFD analysis in a CAD environment gives engineers, designers, and scientists the invaluable ability to visualize fluid flow attributes before physical creation, giving them a host of benefits over traditional experimentation – and we’re just scratching the surface, with many more possibilities to follow in the near future. 

Conclusion ?‍?

CFD analysis software allows you to visualize and analyze problems concerning fluid flow, heat transfer, etc., in your product design. You can solve these issues quickly and accurately to enable safer and quality product design and development.