A High-rise Building Ventilation CFD simulation is a powerful computer model that helps architects and engineers design buildings with better air quality. For tall structures, a Building Ventilation CFD Simulation is essential to understand how wind moves around and through the building. This Tower Ventilation CFD analysis is especially important when the design includes a large central opening, known as an atrium.

This report details a High-rise Building Ventilation fluent simulation using ANSYS Fluent. The goal is to analyze how an atrium can improve a building’s natural ventilation. To create a realistic environment, a special script called a Wind profile UDF was used to model how wind speed increases with height. This type of analysis allows designers to see the performance of their ventilation strategy, ensuring a comfortable and healthy environment for everyone inside. For more HVAC tutorials and CFD simulations, you can visit our HVAC Tutorials to learn about different ventilation techniques.

• Reference [1]: Tai, Vin Cent, et al. “Investigation of varying louver angles and positions on cross ventilation in a generic isolated building using CFD simulation.” Journal of Wind Engineering and Industrial Aerodynamics229 (2022): 105172.
• Reference [2]: Perén, J. I., et al. “CFD analysis of cross-ventilation of a generic isolated building with asymmetric opening positions: Impact of roof angle and opening location.” Building and Environment85 (2015): 263-276.

Figure 1: The 3D geometry of the 7-story building with a central atrium, which forms the basis for this Building Ventilation CFD study.

Simulation Process: Fluent-CFD Setup, Modeling Atmospheric Wind with a UDF

The simulation process for this High-rise Building Ventilation CFD study began with the 3D geometry of the 7-story building, which includes the detailed central atrium and window openings. A high-quality computational mesh was then created using Fluent meshing to accurately represent this complex geometry. A critical step in this simulation was defining a realistic wind condition at the inlet. Instead of a single wind speed, a User-Defined Function (UDF) was written in C programming language to create an accurate atmospheric wind profile. This Wind profile UDF correctly models the real world, where wind speed is slower near the ground and increases with height according to a logarithmic law. This ensures that the forces and flow patterns acting on the tall building are simulated with high fidelity.

Post-processing: CFD Analysis of Atrium-Driven Ventilation

The simulation results provide a complete engineering story, showing how the atrium’s architectural design actively captures wind energy to drive a powerful natural ventilation system. From an engineering viewpoint, the atrium acts as an engine for air circulation. The velocity contours in Figure 2 show that as wind hits the building, it is forced to accelerate over the roof and is also funneled into the atrium. The provided data confirms this effect: while the average velocity in the atrium is 2.16 m/s, the flow accelerates to a peak velocity of 7.165 m/s. This is a dramatic increase, proving that the atrium is working like a “wind scoop” or chimney, pulling a large volume of fresh air into the core of the building.

Figure 2: A wide-view velocity contour from the Fluent simulation, showing the large, low-speed wake that forms behind the building as it obstructs the wind.

Figure 3: A close-up velocity contour, revealing the high-speed airflow (red and yellow zones) as it accelerates over the roof and is funneled directly into the atrium.

The true benefit of this captured airflow is revealed by the streamlines in Figure 3. The high-speed jet of air entering the atrium does not simply pass through. Instead, it creates large, organized, swirling vortex structures that fill the entire height of the atrium. These vortices are the most important feature of the design. They act like large, slow-moving mechanical fans, but without using any electricity. They actively pull the fresh air from the atrium and circulate it across each of the seven floors, ensuring that stale air is pushed out and every part of the building is supplied with fresh air. The complex, swirling lines show that the air is mixing thoroughly, which is excellent for both thermal comfort and indoor air quality.

Figure 4: Velocity streamlines from the Tower Ventilation CFD analysis, visualizing the complex, swirling air circulation patterns created within the building, driven by the atrium.

The most important achievement of this simulation is the quantitative proof that the atrium design successfully creates a self-powered ventilation system. For an architect or HVAC designer, this is invaluable information. It proves that the design will significantly reduce the reliance on mechanical fans, leading to major energy savings and lower operational costs. The simulation provides the exact data needed to optimize the size of the atrium and window openings to maximize this natural ventilation effect, leading to a healthier, more sustainable, and more comfortable high-rise building.