“With Skyscrapers, a windy day is windier”. That was the title of an article published by The New York Times in 1983. It exposed the idea that the windy surroundings of Madison Avenue, downtown NY, were not only a matter of bad weather, but ultimately a consequence of building taller and taller structures.
Half a century later some other skyscrapers where added to that landscape. The city is sure overall denser, and the effects of urbanization can be felt in the messy hairs and broken umbrellas around many corners.
Are windy days even windier than back in the 1980’s? Using Computational Fluid Dynamics and Wind Intelligence, we will now analyze how wind is currently behaving in that area – Madison Avenue from 54th to 94th.
Here are some insights on how wind can drive urban planners to think and design better cities.
For this Wind Analysis we will be looking at the avenue extension between 84th and 95th streets, as well as the nearest parallels, 5th Avenue and Park Avenue.
Computational Fluid Dynamics
For this study we performed a Wind Comfort Simulation with Ingrid Cloud, an automated online platform that performs Computational Fluid Dynamics simulations and combines its results with real life weather data. Implicit LES (Large Eddy Simulations) is the simulation method used as default by the platform.
When simulating wind comfort and wind effects for a chosen location, Ingrid Cloud uses historical weather data provided by meteoblue.com. The weather data is from the 3 years preceding the current year. Wind speed and direction are considered on an hourly basis for each day of the year.
Pedestrian Comfort Criterion
This report is based on Lawson Criteria. A Lawson image will show what type of activity (sitting, walking, etc) is comfortable to exercise at a particular place. Comfort classifications assume that wind velocity exceed the average wind speeds less than 5% of the time considered. In this case, the time considered is a quarter of year, or 3 months. Safety classifications (> 15m/s) are activated when wind velocities exceed the average wind speeds less than 0.022% of the time.
The full simulation report can be accessed here: go to report
This is the most critical period of the year for pedestrian comfort. From the perspective of wind activity, there are many uncomfortable places for pedestrians and a significant presence of potentially dangerous spots.
The statistical metrological data* shows Northwest as the predominant wind direction during Q1 with speeds ranging between 4,5 and 7,5 meters/second.
To better understand the potential consequences of such scenario, we can analyze the movie showing wind effect from that NW direction insolently**.
From Northwest, winds travel freely throughout the open area of Central Park before encountering the buildings facing 5th Avenue. Without barrier to minimalize or spread the flow, the neighborhood is very exposed to those winds.
At 45 East 89th Street a Downwash Effect is observed around one of the highest structures in the area. A 40 stories built in 1969 is acting like a funnel pushing high speeds wind from high altitude, to ground level.
The second quarter brings the lowest magnitude of wind speeds, which by itself produces a comfortable environment. This can be observed with Lawson-based criteria visualization, it displays the scenario with a predominantly blue graph.
The predominant wind direction during Q2 is Southwest. But it’s interesting to note that Southerly wind does not cause the Downwash Effect observed in Q1. The dense surrounding neighborhood plays an important role in protection the area of interest from the prevailing winds during this season.
Ignoring wind is physically dangerous for pedestrians and financially dangerous for the city
Wind is a chaotic phenomenon, hard to predict and analyze. But the complexity of a wind analysis should never overcome the potentially dangerous results of not performing such analysis at all.
Physical dangerous for pedestrians. Financial dangerous for the city. When a business property is not performing well, hardly anyone checks if the pedestrian wind comfort may be the reason. Or even worse, how and if the impact reflects on the city’s overall development.
Take the Downwash Effect happening on Madison Avenue, 45 East 89th Street (the one highlighted during Q1 analysis). It had a significant impact on Carnegie Hill’s Real Estate development.
In order to stop property developers from building more structures that could feed “one of the city’s most vicious wind tunnels”, the neighborhood association set an enormous fight against the Tamarkin Company, the architectural firm who had bought the right to develop a property nearby (the 1269, Madison Ave).
Pressured by the association, in 2001, the landmarks commission unanimously rejected the initial design from Tamarkin, and they had to issue a revised proposal cutting the building from seventeen stories (65 meters) to eleven stories (43 meters).
So, listen to the wind. Understand its effects and optimize city design accordingly.