The Belfer Wind Tunnel, Explained
Between Rubin and Belfer, newly-arrived students have already been greeted by freakishly strong gusts of wind. Even veteran faculty members may wonder why the fury of nature is directed along 184th street, and why our campus was built directly in harm’s way. Has our staunch monotheism offended Aeolus, the Greek god of wind and vowels?
During Hurricane Sandy, students frolicked in the “Belfer wind tunnel,” hoisting themselves up and hanging vertically, or – unfortunately – having one’s glasses blown across the street. The common name hints to the role that the 18 story building named Belfer Hall plays in the construction of this high-speed wind zone, but the atmospheric and meteorological phenomena that work together to create one of the most exciting places on campus in extreme weather deserves further examination.
Technically, these gusts are called “urban winds.” To understand them, remember that air is not just empty space, but rather it is a liquid that flows in three dimensions – not just a direction like north or east, but also up and down. If we could see the different levels of air flowing in different ways above the richly textured urban environment, the level of detail and complexity would fill us with wonder and appreciation.
Urban winds are most significantly caused by the fact that when a building gets in the way of wind flow, the wind does not stop, but finds a new path, like any other liquid. However, air is unlike other liquids because, as an uncompressed gas, it has a very low viscosity. This allows a flow of air to conform particularly well to Bernoulli’s principle, which, for our purposes, means that if a flow is given less space, the speed will increase.
The wind coming off the Hudson, from the east, tends to blow to the west, which allows Rubin and Belfer to act as the walls on a channel carrying wind coming right over the Hudson into Washington Heights, which is more than 200 meters above sea level. Funneling these free and high flowing winds between two relatively large buildings causes them to flow even faster.
A final note on the Belfer wind tunnel: those walking from Belfer to Rubin will note that the high speed wind comes to an end almost as soon as one reaches Rubin. However, walking across the plaza in front of Belfer, one continues to be buffeted by the elements. Why is the Belfer wind tunnel asymmetrical, and why does an 18 story building fail to shield the pedestrians in front of it?
The answer is that the flow of air that has been redirected around Belfer is also 18 stories tall, and after passing Belfer, it flows from the wind tunnel into the space in front of Belfer in an arc. Therefore, in some conditions, safety can only be obtained upon reaching the parking lot, or hugging particularly close to Belfer.