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Here's How Engineers Plan to Stop the Flow of Niagara Falls

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When you want to stop Niagara Falls from flowing, install a cofferdam. The New York State Parks Commission is hoping to do just that as early as 2019.

At a public meeting yesterday, the commission discussed details of a proposal to build two new bridges to replace the existing structures, which date to the turn of the 20th century. The current bridges, which stretch from the mainland to Green Island and from Green Island to Goat Island, are in bad shape: They were temporarily closed in 2004 so that trusses could be installed to stabilize them and allow access to Goat Island, but pieces continue to fall into the water below.

The parks commission determined in 2015 that rehabilitation of the bridges wouldn’t be possible—both the initial construction methods (reinforced concrete with earth-filled arches) and extensive deterioration meant new bridges would be necessary. And to build new bridges, they’d have to dry up the American side of the Niagara River, which sends as much as 150,000 gallons of water per second over the American and Bridal Veil Falls.

To accomplish the dewatering, a temporary cofferdam would be installed, probably at the upstream end of Goat Island. It would stretch from the island—which sits at the edge of the falls and divides the American side from Canada’s Horseshoe Falls—over to the mainland and divert flow from the river entirely to the Canadian side. (Only 15 percent of the falls flow to the American side; 85 percent gushes toward Canada.) 

Once the area is dry, the project could proceed in one of two ways. In the first, the Falls would be water-less from August to December. During that time, the existing structures would be demolished and workers would install piers, according to ABC News Buffalo; water flow would begin again at the end of December, and the next year, workers would resume construction on the bridges. The process would be completed in two years. The second option, which would last a year, would require a nine-month dewatering starting in April and round-the-clock construction.

The commission has been looking at rehabilitating or replacing the bridges since 2009, but the project doesn’t yet have funding and isn’t approved. It estimates that construction costs will range from $21.37 million to $37.32 million, depending on the design chosen, and notes that the state parks department "will need to secure special capital funding from state and/or federal sources prior to advancing this project to the construction phase."

If it does move forward, the work will begin in 2019. It will be the second time the American side of the falls has stopped flowing thanks to humans: In 1969, the U.S. Army Corps of Engineers diverted the flow of the river to the Canadian side using a 600-foot cofferdam constructed of 27,800 tons of rock. The goal? To study the accumulation of boulders and rock from rock slides at the bottom of the falls. The dried-up falls drew many tourists, and after six months of investigation, a decision was made to leave the falls as they were. The cofferdam was removed in November of that year.

You can read the full PDF report of the proposal here.

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Researchers Pore Over the Physics Behind the Layered Latte
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iStock

The layered latte isn't the most widely known espresso drink on coffee-shop menus, but it is a scientific curiosity. Instead of a traditional latte, where steamed milk is poured into a shot (or several) of espresso, the layered latte is made by pouring the espresso into a glass of hot milk. The result is an Instagram-friendly drink that features a gradient of milky coffee colors from pure white on the bottom to dark brown on the top. The effect is odd enough that Princeton University researchers decided to explore the fluid dynamics that make it happen, as The New York Times reports.

In a new study in Nature Communications, Princeton engineering professor Howard Stone and his team explore just what creates the distinct horizontal layers pattern of layered latte. To find out, they injected warm, dyed water into a tank filled with warm salt water, mimicking the process of pouring low-density espresso into higher-density steamed milk.

Four different images of a latte forming layers over time
Xue et al., Nature Communications (2017)

According to the study, the layered look of the latte forms over the course of minutes, and can last for "tens of minutes, or even several hours" if the drink isn't stirred. When the espresso-like dyed water was injected into the salt brine, the downward jet of the dyed water floated up to the top of the tank, because the buoyant force of the low-density liquid encountering the higher-density brine forced it upward. The layers become more visible when the hot drink cools down.

The New York Times explains it succinctly:

When the liquids try to mix, layered patterns form as gradients in temperature cause a portion of the liquid to heat up, become lighter and rise, while another, denser portion sinks. This gives rise to convection cells that trap mixtures of similar densities within layers.

This structure can withstand gentle movement, such as a light stirring or sipping, and can stay stable for as long as a day or more. The layers don't disappear until the liquids cool down to room temperature.

But before you go trying to experiment with layering your own lattes, know that it can be trickier than the study—which refers to the process as "haphazardly pouring espresso into a glass of warm milk"—makes it sound. You may need to experiment several times with the speed and height of your pour and the ratio of espresso to milk before you get the look just right.

[h/t The New York Times]

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Watch NASA Test Its New Supersonic Parachute at 1300 Miles Per Hour
NASA/JPL, YouTube
NASA/JPL, YouTube

NASA’s latest Mars rover is headed for the Red Planet in 2020, and the space agency is working hard to make sure its $2.1 billion project will land safely. When the Mars 2020 rover enters the Martian atmosphere, it’ll be assisted by a brand-new, advanced parachute system that’s a joy to watch in action, as a new video of its first test flight shows.

Spotted by Gizmodo, the video was taken in early October at NASA’s Wallops Flight Facility in Virginia. Narrated by the technical lead from the test flight, the Jet Propulsion Laboratory’s Ian Clark, the two-and-a-half-minute video shows the 30-mile-high launch of a rocket carrying the new, supersonic parachute.

The 100-pound, Kevlar-based parachute unfurls at almost 100 miles an hour, and when it is entirely deployed, it’s moving at almost 1300 miles an hour—1.8 times the speed of sound. To be able to slow the spacecraft down as it enters the Martian atmosphere, the parachute generates almost 35,000 pounds of drag force.

For those of us watching at home, the video is just eye candy. But NASA researchers use it to monitor how the fabric moves, how the parachute unfurls and inflates, and how uniform the motion is, checking to see that everything is in order. The test flight ends with the payload crashing into the ocean, but it won’t be the last time the parachute takes flight in the coming months. More test flights are scheduled to ensure that everything is ready for liftoff in 2020.

[h/t Gizmodo]

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