Scientists to study urban heat island effect using water tunnel

By Brooks Hays  |  June 18, 2018 at 11:05 AM
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June 18 (UPI) -- Scientists in Switzerland have built a water tunnel to study how wind influences the urban heat island effect.

Like many places, Switzerland has experienced increasingly warmer temperatures over the last several years. The problem is pronounced in urban centers.

In cities, rooftops, roads and other forms of built materials, including stone, brick and concrete, absorb more heat than surrounding vegetation, causing temperatures to rise -- a phenomenon called the urban heat island effect.

The heat island effect is problem all over the world, one that taxes electricity grids and increases health risks. Scientists in Switzerland are trying to come up with solutions.

Most efforts to curb the heat island effect rely on incorporating green space into the built environment. Trees and vegetation, in parks, along sidewalks and on rooftops, can help the city reflect more and absorb less heat. Water evaporation on leaves, transpiration, can also encourage cooling.

But scientists at the Swiss Federal Laboratories for Materials Science and Technology, EMPA, set out to study a less utilized cooling resource -- wind. According to researchers, city buildings often prevent winds from gaining momentum. Winds, researchers argue, have the ability to dissipate heat and deliver cooler air from rural surroundings.

Wind can even work in tandem with green space, helping to spread cooler air from nearby parks, lakes and forests throughout the city. For this combination to work, however, researchers say a city's buildings must allow for air masses to move and flow.

To better understand how winds interact with the built environment, researchers at EMPA built a water tunnel. The tunnel, which was inaugurated this week, will help scientists study how roads and buildings effect wind patterns.

Water flows just like large air masses, but at smaller scales, making the phenomenon easier to study in the lab. The water tunnel also allows scientists to simultaneously measure flow patterns and temperature.

To measure flow, scientists use tiny particles and a fluorescent dye. A laser highlights the moving particles, and camera images taken in quick succession allow scientists to play velocity and flow direction.

"Thanks to the fluorescent dye, the researchers can determine the temperature distribution: It absorbs green laser light and emits light of a different color -- the warmer the water, the brighter the light," researchers explained in a news release. "A second camera, which filters out the green laser light, records the emitted light distribution."

Scientists hope their research will reveal new ways to utilize the cooling effects offered by local wind patterns.

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