Computational Fluid Dynamics Modeling in Building Design

Wondering how Computational Fluid Dynamics modeling can be used in development projects to aid cost-effective design? 

What started as a technique for race car airflow simulations is today an increasingly important technique in construction projects. Computational Fluid Dynamics (CFD) has improved a lot over the past few years and its impact will likely only increase when it comes to smart design projects.

Want to learn more about CFD and how it works? Read on!

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Wind-Speed-with-vectors

What are the benefits of CFD?

In construction projects, the benefits of CFD are clear. Thanks to giving designers the tools to visualize a project, CFD helps them understand the impact of design changes, equipment needs, airflow strategies, and energy savings.

CFD enables building designers to:

  • Efficiently evaluate and compare the different options.
  • Reduce the risk of design errors.
  • Complete the project on time and within budget.
  • Comply with regulatory requirements, such as safety and sustainability requirements. 
  • Improve energy efficiency and occupant comfort. 
  • Use the right HVAC solutions to eliminate redundant equipment.

Computational Fluid Dynamics modeling will save costs during the construction project, but also in the long run. Think about it: By coming up with the most cost-effective solutions ahead of time, building operating and energy costs will go down in the long term. 

CFD is an innovative technique that has, and will continue to have as it continues to improve as a technique, a big impact on construction projects. At Alpin, we work with CFD modeling as part of Alpin Innovation Labs, our innovation department for development projects.

Alpin-Commissioning, sustainable, building, management, green

How is CFD used?

CFD plays an important role in the design of thermally comfortable, energy-efficient, and healthy buildings. The building sector is responsible for about 40% of the total energy consumption in the world. Here, CFD can be used to build more sustainable buildings. CFD is also used as a tool to reduce costs and improve building ROI. 

How CFD is used in development projects

The reason CFD is used in building projects is to help the building designer better understand the likely airflow, heat transfer processes, wind conditions and loading (for high-rise), as well as humidity levels in and around a building. This includes the effects of HVAC systems, microclimate, and internal energy sources. 

CFD is used to understand how a building will likely behave under normal and unusual operating conditions. To examine this, different simulation scenarios are used. For example, CFD tests the way the building will behave under different climatic conditions, various levels of occupancy, and so forth. 

In short, CFD is used to study the movement and distribution of air within the building, as well as wind and outdoor local climatic conditions.

The CFD modeling technique is used to model the:

  • Impact of building exhausts to the environment.
  • Quantification of the quality of indoor environments.
  • Design of natural ventilation systems.
  • Smoke and fire risks.
  • Thermal comfort of building occupants.
  • Effectiveness of building services.
  • The build-up of heat in specific places, like server rooms.
  • Shading design effectiveness
  • Wind loading on high-rise buildings
  • Indoor Air stratification effects
  • Outdoor thermal comfort
  • Identify Heat Island effect

CFD is also increasingly used to interact with other models, such as energy consumption and building services models.  

How CFD works 

Now, how does CFD work? A CFD model is created on specialized simulation software. The model is a 3D representation of the project and the area around it (for outdoor CFD study) or the space of interest and the air return/supply points (for indoor CFD study).

A boundary model is used to determine the starting condition of the temperature of these boundaries, the air movement at openings, and air temperature within cells of the 3D model space.

CFD is essentially a mathematical simulation solving millions of equations to simulate air and temperature variations from one cell to another. It also simulates the exchange of heat between boundary surfaces and the cells next to them. Ultimately, this simulation comes to a steady-state. This shows how the actual speed of airflow and the distribution of temperatures within the space.

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This model is then used to make decisions about building design for human comfort and energy efficiency.

How to use CFD in your project

CFD has advanced a lot over the past few years. That’s why today, CFD can be used with simpler and more accessible software.

However, designers typically don’t have the time, knowledge, or resources to use CFD. To get the right results, the software needs to be used by people who understand it. 

That’s why outsourcing this work to CFD experts is a great way to integrate CFD in your project. The important thing is that the expert you choose to work with can demonstrate experience with CFD for projects similar to yours. 

At Alpin, it’s our mission to improve the built environment and to provide healthy and sustainable buildings for all. That’s why we are focused on supporting construction projects to use CFD for the most accurate results. We have a robust internal team who not only understands CFD, but also the development process and how CFD can benefit your bottom line. 

As part of our MEP Technical Advisory services, we use specialized software for CFD analysis, including Envi-Met and IES VE. We have been using Envi-Met to conduct microclimate assessments for outdoor thermal comfort and analyzing how space can be made more conducive to occupants’ comfort requirements, especially for a climate like that in the United Arab Emirates. 

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The software is capable of accurately simulating the outdoor microclimate. This allows us to simulate the building within a dynamic environment, and dive into several aspects of the microclimate to analyze how the designs and buildings will perform and what levels of occupant comfort are achieved in that scenario.

Case study: How CFD was used in the Al Kifaf Towers project 

The Al Kifaf Towers is one of the most prestigious projects in Dubai. The built area is all in all 270,000 m2 and includes four towers. 

Our team at Alpin supported the project with a CFD analysis. A project like this requires all pieces to be in place before the development begins and so CFD modeling was especially important. 

How we used CFD to better understand energy consumption and outdoor thermal comfort conditions

As our Sustainability Analyst Sadaf Ghalib recounts, we performed a microclimate analysis to better understand the effects of building orientation, building massing, levels, and weather conditions on the overall energy consumption, as well as the outdoor thermal comfort conditions. 

This analysis was performed using ENVI-Met, which is a CFD analysis tool capable of simulating outdoor microclimates based on weather data files obtained from ASHRAE Standard 55- 2010 (Thermal Environmental Conditions for Human Occupancy). 

We collaborated with the project team throughout the design stages (pre-design, schematic and detailed design). That’s why we were able to implement strategies that improve outdoor thermal comfort and mitigate factors such as reducing urban heat stress (or urban heat island UHI effect).

We used two scenarios for our analysis: 

A summer simulation (a typical summer day with a temperature range of 28-45 degrees Celsius) and a winter simulation (a typical winter day with a temperature range of 14-32 degrees Celsius). We chose these scenarios to compare conditions for occupants and pedestrians and assess the comfort level they are likely to experience.

The challenges of CFD projects

One of the challenges was that CFD simulations consume a substantial amount of time, so we addressed this beforehand. This goes to show that time management is quite crucial in Computational Fluid Dynamics modeling because you can allow for a contingency plan in case the first round of simulation(s) doesn’t turn out as expected.

Another challenge we faced was unsteady turbulence models. Each simulation can consist of millions of cells and the equations are solved iteratively for each cell, defined by its boundary conditions. This made our analysis more challenging as careful consideration of individual boundary conditions and space parameters are needed due to the project’s massing as it included several closely packed towers and wind tunnel studies.

How we successfully completed the project

We were involved throughout the design process of the Al Kifaf Towers project. During this time, we worked together with architects and other consultants, which helped us understand the intricacies of the design and client expectations. 

This way, we have been able to simulate the design at each stage of the project and propose better strategies, which were then used in the design. 

For example, thanks to our solar analysis, project designers could better determine where shading would be most effective, how green roofs in design could help lower the UHI effect, and if the wind speed is optimum for pedestrians. By analyzing the simulation output files, we were able to better understand interaction factors such as ambient air temperature, wind velocity and relative humidity in and around the site. 

A question we asked ourselves was: “Will the site and buildings be conducive for occupants’ thermal comfort?” After running simulations for different boundary conditions and days of the year, we were able to optimize the design and create a thermally comfortable space within the site. This, by adding shading, can be used as a recreational and social gathering space for occupants throughout the year.

Want to learn more? 

That’s it. Now you know how Computational Fluid Dynamics modeling can help develop more comfortable and sustainable buildings. 

CFD helps you understand building performance before any decisions are made, which improves the construction process and helps designers make the right decisions. In the end, this will lead to cost savings and an increase in building value. 

Want to learn more about CFD? Here’s how you can use CFD in your project.