These days, atrium design considers natural ventilation in addition to light reflection. Residents of high-rise buildings do not benefit from the buoyancy-driven ventilation that comes from having an atrium. One way to increase buildings with varied opening areas at varying heights is to equalize ventilation and thermal comfort on different levels. Based on the novel design of Fini. et al., a CFD simulation is conducted to model Natural ventilation in buildings connected to an atrium. The proposal is published in Energy & Buildings Journal, entitled “ Effects of “wall angularity of atrium” on “buildings natural ventilation and thermal performance” and CFD model”.

• Reference [1]: Fini, Ali Shafiei, and Ali Moosavi. “Effects of “wall angularity of atrium” on “buildings natural ventilation and thermal performance” and CFD model.” Energy and Buildings121 (2016): 265-283.

Figure 1: Geometric description of a two-storied building connected to an atrium [1]

Simulation Process

Although the reference paper designed a three-storied building, a high-rise building is modeled in the present CFD simulation. Figure 5 in the reference paper shows the dimensions of the atrium and buildings. The simulation is indeed carried out in two dimensions, however, for a deeper view, a 3D schematic is shown in the paper and below. The structured grid generation mitigates the cost of simulation.

Post-processing

In this case, the velocity outlines show how the amazing stack effect works, which is hard to see in real buildings but very clear in CFD simulations. Look at how dramatically the colors change in the middle shaft! The air speed goes from almost nothing at the building’s edges to an amazing 2 m/s in the vertical chimney (red center). Not only is the speed interesting, but so is the beautiful flow pattern. Each floor has holes on the sides that let in fresh air. You can see the light blue streams (0.5–0.8 m/s) that come into each room. The symmetrical design is great for natural ventilation because the streamlines show that air flows smoothly through each level without causing drafts or areas where air doesn’t move. Even more telling: have you seen how the flow paths are becoming rounder in each room? That’s exactly what builders want: air to flow around every corner instead of following straight lines that would leave empty spaces.

Figure 2: Room ventilations driven by natural convection inside the buildings

The temperature visualization tells the other half of the story about how thermal buoyancy powers this ventilation system without a single mechanical fan. The coolest air (deep blue, around 15-20°C) enters through the lower openings, while warmer air (lighter blue, 30-40°C) naturally rises through the central shaft. This temperature gradient is the invisible engine driving everything. Heat enters through windows and is generated by occupants, creating warmer, less dense air that wants to rise. The genius of this design is how it channels this natural movement—the slightly higher temperatures along each ceiling (about 5-8°C warmer than floor level) create gentle pressure differences that keep air flowing upward. Rather than fighting physics, this building harnesses it, demonstrating why passive design approaches can maintain excellent indoor air quality while slashing energy costs compared to mechanical systems.

Figure 3: Thermal comfort inside the building in terms of temperature