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September 2019

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Luma Bendini

MAD WINDS: a wind analysis at Madison Avenue

A Wind Analysis on Madison Avenue and how it affects pedestrians, real estate and urbanisation.

 

“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 urbanisation 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, let's analyse 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.

The area of interest

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.

 

Methodology and input data

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.

Weather Data

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 exceeds 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.

Visualisation Report

The full simulation report can be accessed here: go to report

Tetrahedral mesh in cross sections perpendicular to the axis

Tetrahedral mesh in cross sections perpendicular to the axis.

 

Q1 | January, February and March

Lawson-based Criteria, Q1 Height: 2m

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 meteorological data shows Northwest as the predominant wind direction during Q1, with speeds ranging between 4.5 and 7.5 metres/second.

To better understand the potential consequences of such scenario, we can analyse the video showing wind effects from that NW direction.

Wind Rose for Q1: dominant winds from Northwest
 
windeffects-northwest-2m-edit (1)

Wind Rose Graph and Wind Effects Video:

From Northwest, wind travels freely throughout the open area of Central Park before encountering the buildings facing 5th Avenue. Without a barrier to minimise or spread the flow, the neighbourhood is very exposed to those winds.

 

At 45 East 89th Street a Downwash Effect is observed around one of the tallest structures in the area. A 40-storey building built in 1969 acts like a funnel, pushing high speed winds from higher altitudes to ground level.

Downwash Effect on 45 East 89th Street
 
Downwash Effect on 45 East 89th Street

Downwash Effect at 45 East 89th Street

 

Q2 | April, May, June

Lawson-based Criteria, Q2 Height: 2m

The second quarter brings the lowest magnitude of wind speeds, which by itself produces a comfortable environment. This can be observed with a Lawson-based criteria visualisation. 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 neighbourhood plays an important role in protecting the area of interest from the prevailing winds during this season.

 
Wind Rose for Q2: prevailing winds from Southwest and South
 
Wind Effects, Southwest Q2 Height: 2m
 

Wind Rose Graph and Wind Effects Picture:

The entire area displays an overall comfortable wind experience for pedestrians. This is a desirable result, considering that Q3 corresponds to a warmer season and outdoor activities are expected.

Wind direction during Q3 are predominantly from Southwest with a magnitude of 2.5 metres/second.

Wind Rose for Q3: dominant winds from West, Southwest and South

The entire area displays an overall comfortable wind experience for pedestrians. This is a desirable result, considering that Q3 corresponds to a warmer season and outdoor activities are expected.

Wind direction during Q3 is predominantly from Southwest with a magnitude of 2.5 metres/second.

Wind Rose for Q3: dominant winds from West, Southwest and South

Conclusion

 Ignoring wind is physically dangerous for pedestrians and financially dangerous for the city. 

Wind is a chaotic phenomenon, and is hard to predict and analyse. But the complexity of a wind analysis should never overcome the potentially dangerous results of not performing such analysis at all.

It's physically dangerous for pedestrians and financially 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 at Madison Avenue, 45 East 89th Street (the one highlighted during the 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 neighbourhood association set an enormous fight against the Tamarkin Company- the architectural firm who bought the right to develop a nearby property (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 metres) to eleven stories (43 metres).

So, listen to the wind. Understand its effects and optimise city design accordingly.

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