- When open-air spaces in cities are closed, the air moves in a vortex and the air stays inside the box-shaped space for a long time.
- Researchers have developed a shutter that can increase the air flow of these spaces using the kirigami technique.
- This innovation aims to ventilate urban canyons and reduce temperature rise in cities.
Researchers at the Princeton School of Engineering discovered that placing a specially designed lid on top of a box can significantly increase airflow from wind blowing over the top surface. This isn’t just a show gimmick. This information could help clean and cool urban canyons in cities like New York and Hong Kong and improve ventilation at pop-up restaurants and bus stops.
A study published in the Journal of Wind Engineering and Industrial Aerodynamics in the article researchers; They demonstrated that a lid with evenly spaced inclined slats, called louvers, can increase airflow in a box by channeling wind that would normally pass through the open top. The researchers further modified the geometry of the top using the Japanese art form kirigami. Kirigami artists shape paper by cutting and folding. This technique allowed the researchers to stretch and bend the louvers in new shapes in 3D, further increasing the amount of air moving through the box.
Researchers were initially looking for a way to improve the outdoor venues that have popped up on city streets during the COVID pandemic. These small structures, which offer outdoor seating during COVID, were often stuffy when the windows were closed. The researchers wanted to find out whether tidying up the roof could offer a solution.
The main air flow pattern of open-top spaces is circular and swirly. Some air exchange occurs at the top, but most of the air remains inside the box for a long time. The research improves understanding of urban warming in a warming climate. Studies describe how concrete buildings and asphalt roads in cities create heat islands that concentrate heat during hot seasons.
For this project, researcher Elie Bou-Zeid and his colleagues wanted to know whether shutters could increase both air circulation and shade in urban canyons. The researchers began by examining how a traditional louver with unidirectional inclined plates could be adjusted to affect airflow.
Lucia Stein-Montalvo, an expert on the solid mechanics of kirigami, and co-researcher Liuyang Ding used a set of boxes and shutters made of acrylic. Wind tunnel tests, as well as computer simulations, allowed the team to study how inclined boards change the dynamics of moving air. Airflow inside the box was maximized by adjusting the louvers. Using the Kirigami method, the panels that make up the shutters were arranged so that the air follows the inside and outside, respectively.
Stein-Montalvo noted that future projects will investigate patterns and materials suitable for use in cities and large structures: “The aim of this paper was to demonstrate the effectiveness of kirigami, but there is still room for optimization. “Next research will focus on more realistic environments such as urban canyons and consider materials as well as structural stability on a larger scale.”
Compiled by: Esin Özcan