The Invisible Force
David Zhuoyue Duan
Award: Top 100
School: the village school
Teacher: fabian ng
Category: Contrived
Photo #20850
The Invisible Force
For this photograph, I used a wind tunnel and smoke visualization to reveal how air interacts with a skyscraper-shaped model. Wind is usually invisible, but the smoke turns the air into lines, curves, and swirls, allowing complex aerodynamic phenomena to be observed directly.
The inspiration for this image came from New York City's famous Citicorp Center. During the 1970s, engineers discovered that certain wind directions could generate structural loads much larger than expected. This event became one of the most well-known examples of the importance of wind engineering in modern architecture.
As air approaches the model, it slows down at the front surface, creating a stagnation region where kinetic energy is converted into pressure. The airflow is then forced around the sides and over the top of the structure. Because air cannot follow the sharp edges perfectly, the boundary layer separates from the surface, forming a turbulent wake behind the building.
The swirling smoke visible behind the model reveals regions of vortices and low pressure created by this flow separation. These vortices are responsible for fluctuating aerodynamic forces that can induce vibrations in real buildings. Engineers must carefully account for these effects when designing tall structures to ensure both safety and comfort.
This photograph captures the hidden conversation between wind and architecture. It shows that a skyscraper is never truly still. Even when we cannot see it, physics is constantly pressing, pulling, and reshaping the structures of our cities.
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