NASA research now helps aircraft manufacturers deal with the dangers of supercooled water in the atmosphere.
Here’s a simple science experiment to try at home: Place an unopened bottle of distilled water in your freezer. After 2–3 hours, if the water is pure enough, it won’t have frozen. Then, carefully pour the water into a bowl with a piece of ice in it. The instant the water strikes the ice, it will freeze.
Though we have all been taught from an early age that water freezes at 32 °F, this is not always the case. Ice crystals form around impurities, so any water lacking them can be supercooled to even lower temperatures without freezing.
High in the atmosphere, water droplets often achieve this delicate, supercooled state. Then, when a plane flies through clouds containing these droplets, the water strikes the airframe and freezes instantly. The ice buildup negatively affects the aerodynamic performance of the plane and can even present safety concerns when ice forms inside the engine.
NASA has long studied ways of detecting and countering atmospheric icing conditions as part of the Agency’s efforts to enhance aviation safety. To do this, the Icing Branch at Glenn Research Center utilizes a number of world-class tools, including the Center’s Icing Research Tunnel and the NASA 607 icing research aircraft, a “flying laboratory” for studying icing conditions. The branch has also developed a suite of software programs to help aircraft and icing protection system designers understand the behavior of ice accumulation on various surfaces and in various conditions.
Breaking the Ice
One of these innovations is the LEWICE ice accretion simulation software. Initially developed in the 1980s (when Glenn was known as Lewis Research Center), LEWICE has become one of the most widely used tools in icing research and aircraft design and certification.
The program provides a virtual simulation environment for determining where water droplets strike an airfoil in flight, what kind of ice would result, and what shape that ice would take. Users can enter geometries for specific, two-dimensional cross sections of an airframe surface and then apply a range of inputs—different droplet sizes, temperatures, airspeeds, and more—to model how ice would build up on the surface in various conditions.
The program’s versatility, ease of use, and speed—LEWICE can run through complex icing simulations in only a few minutes—have contributed to it becoming a popular resource in the aviation industry. The software is freely available and is distributed to everyone from graduate students at universities to multimillion-dollar companies.
One such user has capitalized on the capabilities of LEWICE, developing a toolset with the potential to enhance the utility of the NASA-developed software.
An Indispensable Tool
“I execute literally thousands of runs of LEWICE every year,” says David Parkins, founder and president of American Kestrel Company LLC. Based in Ithaca, New York, American Kestrel provides research and development and consulting services to aircraft manufacturers in the field of aviation safety and icing.
Parkins has long used the NASA software to help his company’s customers design safe aircraft that can meet rigorous certification standards for flight in icing conditions. He also saw room for improvement with the program’s user interface and began developing tools to facilitate the plotting and running of the code. Parkins shared the results with Glenn, and the Center formed a partnership with American Kestrel through a Space Act Agreement, allowing the company to distribute LEWICE internationally with the new interface.
American Kestrel’s LEWICE Interface (LEWINT) combines LEWICE with an enhanced user interface, icing analysis tools, and automated plotting. Parkins estimates that by using the software, American Kestrel’s customers save hundreds of thousands of dollars in costs by reducing tunnel testing and precluding expensive, late stage design changes.
“Within the United States, every airframer uses LEWICE from Glenn, or LEWINT from American Kestrel,” Parkins says. “Glenn has some of the best icing researchers in the world at one of the best icing facilities in the world working on that software, and they have evolved it into a very robust tool.”
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