Test rides on the six-axis simulator are meant to simulate the flight of electric vertical takeoff and landing (eVTOL) aircraft in order to help NASA study turbulence on planned air taxi services in New York, Chicago, Los Angeles, and elsewhere in the U.S. The data will be shared with AAM industry partners to help them develop passenger-friendly designs.

The space agency is working with several major air taxi developers through its advanced air mobility (AAM) mission, including Archer Aviation, Joby Aviation, and Boeing eVTOL arm Wisk Aero, to research the experience and safety of riders as well as onlookers on the ground.

“The experiments in the ride quality lab will inform the advanced air mobility community about the acceptability of the motions these aircraft could make, so the general public is more likely to adopt the new technology,” said NASA test pilot Wayne Ringelberg.

Ringelberg served as the passenger for the comfort experiment. The pilot recently flew a series of test rides on the new simulator at NASA’s Armstrong Flight Research Center in Edwards, California, to help prepare it for trials with actual test subjects.

Ringelberg lifted off from a NASA-designed conceptual vertiport atop a downtown San Francisco parking garage, flying over the city to another virtual takeoff and landing site on top of a skyscraper. Sitting in a seat mounted on a six-axis platform that recreates the full range of motion of an air taxi ride, he wore headphones to simulate noise and VR goggles that gave him a view of the cockpit and the city below.

Following the flights, Ringelberg reported to NASA on how realistic and reliable the simulator’s movement and audiovisual cues were.

“This project is leveraging our research and test pilot aircrew with vertical lift experience to validate the safety and accuracy of the lab in preparation for test subject evaluations,” he said.

With Ringelberg’s work finished, the agency will soon begin testing with human subjects. They will similarly wear a VR headset and headphones, flying the same route as the NASA test pilot. During the flight, subjects will press a button to indicate discomfort.

The space agency will analyze those responses and try to match them to the user’s heart rate, breathing rate, and experience of motion or audiovisual stimulus. It will make that data available to air taxi manufacturers and other industry stakeholders to shape flight paths through cities, identify takeoff and landing spots, and guide air taxi design elements like window size and seat placement.

The air taxi simulator is the key component of NASA’s rider quality lab, but that project is itself only a tiny piece of the agency’s AAM mission.

It began using the term AAM in 2020 and has since worked with stakeholders across the industry on a wide range of projects. The initiative focuses on everything from air taxi safety and ride quality to travel time, automation, and infrastructure such as vertiports, preparing industries including healthcare, emergency response, and cargo delivery for the introduction of the novel aircraft.

Within the program is the Advanced Air Vehicles Program (AAVP), which focuses on innovative aircraft designs such as Revolutionary Vertical Lift Technology (RVLT). In addition to passenger comfort, NASA under the RVLT umbrella has studied air taxi batteries, noise, and traffic, particularly around busy airports like Dallas-Fort Worth International Airport (KDFW).

Urban air traffic management and the integration of eVTOL designs into air traffic control operations and the national airspace system is a major part of the space agency’s mission. It aims to complete its research in time for the U.S. to develop a robust air taxi industry by the end of the decade.

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Significant turbulence events are not particularly uncommon – a Hawaiian Airlines flight made headlines last year, and a Southwest flight was forced to divert due to turbulence earlier this spring – but the Singapore Airlines flight brought the first turbulence-related fatality in years.

• READ MORE: Severe Turbulence Blamed in Death Aboard Singapore Airlines Flight

This flight begs the question of how pilots, dispatchers, air traffic controllers, and other stakeholders can predict turbulence and avoid it. Detecting turbulence can be difficult, and not all turbulence is predictable, but there are ways to identify where it could occur.

Convective Activity

The biggest indicator of turbulence is convective activity. When unstable air is allowed to rise – by a lifting force such as a front or a mountain range – its movement becomes what we call turbulence. Pilots can identify where convective action is occurring to pinpoint areas where they could experience turbulence.

The easiest way to identify areas of convective turbulence is to look at clouds. When clouds become vertically developed – when they extend high into the sky in puffs – it is likely that turbulence is present because air needs to be pushed upwards considerably to allow moisture to condense into towering clouds. The same is true with heavy, showery rain: such comes about when air is forced upwards enough to create rain. In heavy storms, the turbulence is compounded by downdrafts that force rain to the surface, passing through the updrafts that allow the storm to develop in the first place.

Mountain Waves

Another place where turbulence is common is over mountain ranges. Mountains provide a natural lifting mechanism for unstable air, allowing air to rise and move around more strongly. This extra movement is often most noticeable the closer you are to the mountains, which is why mountainous areas often have the bumpiest takeoffs and landings. These are commonly referred to as mountain waves.

Pilots have additional tools to help them predict turbulence. In the United States, the Aviation Weather Center – part of the National Oceanic and Atmospheric Administration (NOAA) – creates aviation-specific weather reports and forecasts to help crew identify weather patterns conducive to atmospheric instability.

• READ MORE: Treat High-Altitude Turbulence with Knowledge and Respect

Most important are inflight aviation weather advisories called AIRMETs, SIGMETs, and Convective SIGMETs. AIRMETs apply mostly to smaller aircraft; they pertain to activies such as areas of low clouds and visibility and moderate turbulence. SIGMETs and Convective SIGMETs apply to all aircraft regardless of size.

Convective SIGMETs are the most applicable for finding areas of extreme turbulence. They may be issued for things such as lines of severe thunderstorms called squall lines; tornadoes; embedded thunderstorms; surface winds greater than 50 knots; and more. These provide pilots with information on the areas most critical to avoid inflight.

New Tools Available

There are also third-party apps that help crews and even passengers, predict where the smoothest rides will be. They take weather and pilot reports to make assessments and predictions about where the smoothest rides will be, allowing for safer, more comfortable trips. They also use real-time data to cross-check the accuracy of their systems.

In addition, pilots are able to use a reporting system – called PIREPs – to warn others of their observations, including icing and turbulence. Crews use these reports and predictions to make decisions about which routes to take, which altitudes to fly, or even whether to fly at all.

• READ MORE: ForeFlight Introduces Reported Turbulence Map

Not every bit of turbulence is predictable, though. There is another type of turbulence called “clear air turbulence” that can seemingly appear out of nowhere and will not show up on radar. This type of turbulence tends to take pilots by surprise and does not provide any possibility of avoidance. This is a big reason why pilots and cabin crew tell passengers to fasten their seatbelts whenever seated, even if the seatbelt sign is off: if turbulence suddenly takes an aircraft by surprise, passengers reduce their own risk if they are already strapped in.

Severe and extreme turbulence events are still exceedingly rare in the context of how many commercial flights operate each day.

Editor’s Note: This article first appeared on AVweb.

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“No one enjoys flying through turbulence, whether you’re piloting a single-engine piston or riding in the back of a jet,” said Henrik Hansen, ForeFlight’s chief technology officer.

ForeFlight says the additional feature within the mobile app displays the measured intensity of turbulence at multiple altitudes, making it easy for pilots to find the smoothest altitude along their flight path. ForeFlight Mobile automatically uploads the reports once it establishes an internet connection after the flight or instantly if connectivity is maintained during flight, according to officials.

Turbulence reports are depicted as colored markers on the Maps tab: Gray signifies smooth air, while yellow, orange, and dark orange represent increasing levels of turbulence, ranging from light to severe.

While pilots traditionally rely on weather forecasts and PIREPs for route planning, ForeFlight says its Reported Turbulence method offers distinct advantages, including enhanced accuracy and objective reporting.

ForeFlight estimates its Reported Turbulence layer offers 50 times more turbulence reports than manual PIREPs, per Sporty’s IPAD Pilot News.

Reported Turbulence is available as two add-ons for Pro Plus subscribers. Reported Turbulence (Low) offers access to turbulence reports up to 14,000 feet, whereas Reported Turbulence (All) provides access to reports across all altitudes.

Editor’s Note: This article first appeared on AVweb.

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My ride that day was a brand-new Piper Archer, N2876K. It was well equipped for that era; it even had a two-axis autopilot and DME—a luxury in those days. The flight was planned for four hours plus, with a stop in Indianapolis for fuel and to check weather at the Combs Gates FBO. I filed my first solo instrument flight plan and departed at 8:30 a.m. local. The weather was VFR all the way to Indianapolis International Airport (KIND)with only early morning haze to contend with. After picking up my IFR flight plan from Cleveland Departure, I climbed with the sun at my back into a cloudless blue sky. I felt like I belonged.

A quick 2 hours and 15 minutes later, I was taxiing up to Combs Gates with a real sense of accomplishment, maybe even more than four days earlier when I passed my checkride. After all, I was flying in the “system” with no supervision—entirely on my own. However, that was about to change. The next segment between Indianapolis and 50 miles east of St. Louis produced one of those life-altering moments for an aviator, one that shaped every aspect of my future flying career.

As I topped off the tanks and had a sip of Coke, I had a pleasant conversation with a flight service specialist who gave me a standard briefing that included: “VFR along the entire route but with a chance of isolated thunderstorms.” Your typical Midwest summer forecast.

Fair weather cumulus started to form, but nothing in the briefing hinted at a go/no-go decision. In fact, the briefer mentioned the cloud bases reported along the route were at least 7,000 feet. Just for safety, I filed for a westbound altitude of 6,000 feet on Victor 14. I wanted to be on an IFR flight plan—just not hard IFR.

I headed west above the haze and leveled at 6,000 feet. As I approached Terre Haute, Indiana, I saw a confusing solid wall of clouds extending many thousands of feet above my altitude. The clouds didn’t look like cumulus. A quick call to Indianapolis Center confused me even more. The controller said he wasn’t “painting” any weather from my position all the way to St. Louis.

At this point, I considered canceling IFR and landing at Terre Haute. But I scrapped that idea. My ego got in the way. After all, I had just passed my check ride in actual, and I was beaming with confidence. Onward I flew into the cloud bank. The initial ride generated an occasional bump at worst. I felt confident I had made the correct decision to continue. I couldn’t have been more wrong.

Soon I was handed off to Kansas City Center over eastern Illinois. By this time, the Archer was jolted by continuous moderate turbulence. My confidence quickly turned into real concern. I keyed the mike and asked the new controller about the weather in front of me, but he only came back with “light to moderate” precipitation for the next 50 miles. At this point, the airplane was still on autopilot and handling the chop and occasional upset.

Then the situation got worse. Torrential rain, continuous lightning, severe turbulence, and—most upsetting to me—the vertical speed indicator was first pegged up to the stops and then pegged in the opposite direction. I reduced power for an indicated airspeed lower than maneuvering speed (V_A), but I knew I was in trouble. I was convinced the wings were going to separate from the airframe. I felt more like a helpless passenger than PIC.

I called Kansas City Center again, but this time I confessed my unfortunate position. I was on the verge of tears. There was little or no controlling my altitude. The updrafts and downdrafts were so strong I knew any attempt to maintain altitude would cause a break up.

• READ MORE: Racing a Storm Is Not the Best Choice

I needed help, quickly. The controller sensed the urgency in my transmission and calmly said, “Stand by.” A few moments later, the controller handed me off to a new one. I was to be his only customer, and he volunteered that he was only “painting” light to moderate precipitation, but I told him the airplane was in severe updrafts and downdrafts. He said to keep the wings level, and he would try to steer me clear of the heaviest precipitation.

Time stood still. I have no recollection of how long he vectored me. He kept saying not to worry about altitude and just try to keep the wings level. The controller continued to “suggest” headings followed by “How’s the ride now?” I wasn’t reassured, but I did robotically turn as suggested, all the time going up and down the elevator. I was soaked through with perspiration and exhausted.

This went on until just south of Litchfield, Illinois, when he cleared me down to the minimum en route altitude (MEA), and I broke out of the cloud bases. Now I had a fighting chance of surviving. There was lightning in all quadrants and sheets of virga I had to dodge, but that was manageable. While the updrafts and downdrafts had subsided, there still was continuous moderate-to-severe turbulence. My head hit the side of the airframe, the headliner, and the glareshield. And without warning, just as I was handed to St. Louis Approach, the airplane broke out into CAVU VFR.

I landed at Spirit of St Louis Airport with the aircraft in one piece—but I was scarred for life. I had been sure I was going to die and would be just another low-time pilot who flew into a thunderstorm. I was so grateful the controller had helped me through, but I knew I would never look at instrument flying the same way. Thousands of hours later, I am still haunted by that flight.

This article first appeared in the July 2023/Issue 939 print edition of FLYING.

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Unsurprisingly, choppiness also occurs due to updrafts or downdrafts created by storms. In recent years, however, there’s growing evidence that climate change is causing more inclement weather—and by extension, more turbulence.

But what if we could get rid of that bumpiness for good? In a viral video that has racked up more than 3.2 million views on X (formerly Twitter), Austria-based Turbulence Solutions gave a sneak peek of its Turbulence Canceling solution, which got its first customer earlier this year. The Vienna startup plans to use a combination of sensors, lidar, and flight control software to reduce the effects of turbulence by measuring, predicting, and mitigating choppiness.

Andras Galffy, founder, CEO, and head of technology and research at Turbulence Solutions, told FLYING the company first plans to integrate its solution on GA aircraft, as well as electric vertical takeoff and landing (eVTOL) aircraft for planned advanced air mobility (AAM) services.

“Even without climate change increasing turbulence, especially for light and small aircraft flying low and fast, comfort is a showstopper.” Galffy said. “A very limited number of passengers enjoy flying GA aircraft for comfort reasons. AAM and eVTOL will need to provide turbulence-free ride quality and passenger comfort for returning and recommending customers.”

Galffy, who earned his doctorate in flight control from Vienna University of Technology’s Automation and Control Institute, founded Turbulence Solutions in 2018. But the company appears to have emerged from stealth in 2022, when it began circulating the now-viral video on LinkedIn and posting on Facebook and X.

According to its website, Turbulence Solutions has already obtained a U.S. patent for its solution, with a few others in the application process. It also tested the system on board a crewed demonstrator aircraft, which it used to gather in-flight data, in 2021, Galffy said.

Based on that data, the company predicts Turbulence Canceling will reduce the load felt by passengers by more than 80 percent, though the system is a comfort feature and won’t be required for operation. The company said it will use a feedback and “feedforward” approach, combining dynamic lift control with predictive sensor technology.

The solution’s Turbulence Load Prediction component will provide the “feedforward,” anticipating choppiness in front of the aircraft. Pressure sensors and wind lidar technology will combine to measure differential pressure ahead of the wing, predicting vertical acceleration to an estimated 1 m/s/s degree of error, the company claims.

That system will send feedback to a Direct Lift Control system, which dynamically adjusts wing shape within fractions of a second (as a bird does) to reduce inertia on the flaps and stabilize angle of attack. This component will incorporate flight dynamics beyond wing root moments, including vertical acceleration, pitch, roll, and wing bending. It can be integrated on aircraft with conventional flaps or enable wing morphing.

Galffy contrasted this strategy with conventional turbulence avoidance methods, which often involve pitching the entire aircraft via elevator input. This, he said, is simply too slow of a reaction to avoid choppiness.

How Pilots Handle Turbulence

By and large, pilots know what to do when they encounter turbulence, but existing mitigation strategies aren’t exactly ideal.

Chapter 12 of the Pilot’s Handbook of Aeronautical Knowledge introduces the concept of turbulence and educates about its causes and effects. Typically, the initial course of action is to slow to maneuvering speed—fast enough to keep the aircraft in level flight, but slow enough to escape structural damage from choppiness. 

Pilots are required to know this speed, which is specified by aircraft gross weight in the Pilot’s Operating Handbook and is commonly placarded in the cockpit: the heavier the aircraft, the higher the maneuvering speed. 

The strategy is similar to driving slowly on a bumpy road to avoid dents from potholes. For passengers, however, this can cause discomfort or raise concerns about the aircraft’s safety.

Less frequently, pilots will take a different road entirely; that is to say, they will adjust course or altitude to avoid the turbulence altogether. But for large aircraft in particular, rerouting can strain fuel requirements and increase carbon dioxide emissions. And for smaller aircraft traveling short distances at low altitude, it’s a near-impossible task, Galffy said.

In short, there is no simple recourse for pilots who encounter choppiness. On its website, Turbulence Solutions points out that eVTOL designs are also susceptible to turbulence. These aircraft are relatively light but cruise at high speeds, and turbulence could tank customer satisfaction or limit the availability of planned AAM services.

Galffy told FLYING the company has already developed systems to sufficiently reduce turbulence for light and eVTOL aircraft. This year, the startup picked up its first customer: a manufacturer of 1,300-pound ultralights. 

Next up will be adding fail-operational capabilities to integrate Turbulence Canceling on larger models. Galffy mentioned business jets and airliners as potential customers. For now, though, the focus is on a simpler system for GA and eVTOL aircraft, which the CEO said is easier to certify.

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According to the FAA, around 4 p.m. on March 3, the Bombardier Challenger CL30 with three passengers and two crew members on board, was flying from Dillant-Hopkins Airport (KEEN) in Keene, New Hampshire, to Leesburg Executive Airport (KJYO) in Virginia when it encountered severe turbulence. The crew diverted to Bradley Field, Windsor Locks (KBDL) in Connecticut. One of the passengers was fatally injured during the incident.

The FAA and the National Transportation Safety Board are working together on the investigation, with the NTSB taking the lead role. The name of the person fatally injured has not been released.

The NTSB will be analyzing information from the flight data recorder, cockpit voice recorder, and weather at the time of the incident, the agency told FLYING in a statement. A preliminary report is expected to be available in two to three weeks.

Defining Turbulence

In its educational materials, the FAA defines turbulence as “air movement created by atmospheric pressure, jet streams, air around mountains, cold or warm weather fronts, or thunderstorms.”

The FAA has defined the intensity of turbulence as follows:

• Light Chop: Slight, rapid, and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude.
• Light Turbulence: Slight, erratic changes in altitude and/or attitude. Occupants may feel a slight strain against seatbelts. Unsecured objects may be displaced slightly. Food service may be conducted and little to no difficulty is encountered in walking.
• Moderate Chop: Rapid bumps or jolts without appreciable changes in aircraft altitude or attitude.
• Moderate Turbulence: Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed, food service and walking are difficult.
• Severe: Large, abrupt changes in altitude and/or attitude. Usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. Occupants are forced violently against seatbelts. Unsecured objects are tossed about. Food service and walking are impossible.
• Extreme: Aircraft is violently tossed about and is practically impossible to control. May cause structural damage.

Earlier in the week, seven passengers aboard a Lufthansa Airbus A330 enroute from Austin, Texas, to Frankfurt, Germany, were injured when the aircraft encountered severe turbulence. The aircraft was diverted to Washington Dulles International Airport (KIAD).

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Answer:

If you are a brand new pilot or even one that has a few thousand hours recorded in your logbook, eddy dissipation rate or EDR, is not likely part of your aviation vocabulary. However, if you use aviationweather.gov, the EZWxBrief progressive web app (ezwxbrief.com) or one of the many heavyweight flight planning apps, you have likely stumbled across this relatively new “aviation” term. Let’s define EDR and explore how it should be used by GA pilots.

When confronted with moderate or greater turbulence while in flight, the first response is to slow down below the aircraft’s maneuvering speed, or what is sometimes called turbulence penetration speed. But maneuvering speed is directly dependent on the aircraft’s weight. In other words, the heavier the aircraft, the higher the maneuvering speed. By reducing airspeed, the goal is to reduce the forces (or load) on the aircraft parts that could fail as the aircraft accelerates and decelerates in moderate or greater turbulence. Keep in mind, this is less about the wings falling off and more about the engine mount or other parts failing during an encounter with a jarring turbulence event. Therefore, how can turbulence be quantified for the specific aircraft you fly?

This is the job of EDR. EDR is an aircraft-independent meteorological field expressed in m²/s³ (meters squared per seconds cubed). Simply put, an atmosphere that causes eddies to dissipate rapidly is one that is likely turbulent. Most importantly, EDR is not a measure of the likelihood of turbulence, just the intensity. 

In fluid dynamics, an eddy is the “swirling” of a fluid. Given that air has similar properties as a fluid, there are also eddies in the atmosphere. It’s likely you have seen pictures of wake vortices swirling off the wingtips of a large turbofan aircraft as it passes through clouds or perhaps smoke. It’s important to avoid these wake vortices (which are usually invisible) since they can cause a smaller aircraft following the jet to enter an uncommanded roll. This is referred to as wake turbulence.

• READ MORE: Why Does the Pilot in Command Sit on the Left Side of the Cockpit?

In that light, you must pay close attention to the wind with respect to wake turbulence. This is because the prevailing current of wind will cause these vortices to “drift” downwind. If the wind is calm or nearly so, these vortices can persist over the area of concern for some time. Stronger winds will cause the vortices to move farther away from the area and eventually mix out more quickly with time.

Most eddies in the atmosphere do not manifest themselves like these wake vortices. However, imagine such a vortex or “eddy” in the atmosphere. A turbulent atmosphere will cause the eddy to quickly dissipate, whereas an atmosphere with little or no turbulence will allow the eddy to persist. Most importantly, the eddies must be on the scale of the size of the aircraft for you to feel a bumpy ride in the cockpit. From a forecast perspective, nobody is generating eddies in the atmosphere and watching what happens to them, but instead, they are determining what conditions in the atmosphere cause air to mix. An atmosphere that is mixing quite a bit is one that is likely turbulent. EDR is just a measure of how “mix-y” the atmosphere is, or how fast the atmosphere will mix out these eddies, hence the s³ (seconds cubed) in the unit’s denominator. 

EDR is an observed or forecast value that is between 0 and 1 with 0 representing perfectly smooth air and 1 implying supercell thunderstorm level of mixing. It is not critical to understand how this EDR is determined. The EDR value used throughout the EZWxBrief progressive web app is actually EDR x 100. Multiplying EDR by 100 provides a way to turn this into an integer value from 0 to 100 to make it easier to use. For example, an EDR value of 0.23 m²/s³ will be adjusted to 23. 

EDR is not a “one size fits all” kind of weather parameter such as ceiling or visibility. That’s the tricky part of EDR. As mentioned earlier, the turbulence penetration speed is directly related to the weight (class) of the aircraft. So, this means that a pilot flying a Cessna 152 is going to experience turbulence that’s different from a pilot flying a Gulfstream G600. And a Gulfstream G600 will experience turbulence that’s different than an Airbus A320. And an Airbus A320 will experience turbulence that’s different than a Boeing 777. This means an EDR value of 18 may produce moderate turbulence for a Cirrus SR20, but will be considered light turbulence for a Boeing 737.

There are three aircraft weight classes in the table below. These include light, medium, and heavy based on the aircraft’s maximum takeoff weight.

• Light < 15,500 pounds (e.g., Piper Cub, Cirrus SR22, Lear 23)
• Medium (or large) 15,500 to 300,000 pounds (e.g., A320, B737, GV, MD80)
• Heavy > 300,000 pounds (e.g., A330, A380, B787, B777)

This table is based on the results of a study done by turbulence researchers at the National Center for Atmospheric Research (NCAR). According to Dr. Robert Sharman, who participated in this study, the idea was to compare pilot weather reports (PIREPs) with in situ EDR data for the same location and altitude. But they only had medium weight class data (e.g., B737) for comparisons, and the statistical spread was quite large. So, these researchers used the medians for comparison. Then they used a theoretical argument about aircraft response based on weight to extend the mapping to include light and heavy class aircraft. It is important to understand that the EDR ranges for light and heavy aircraft weight classes in the table above have never been verified, and would be extremely difficult to do without a lot of data that simply doesn’t exist. Therefore, for light and heavy aircraft, these are educated guesses. In other words, your experience may vary. 

In the end, the EZWxBrief vertical route profile shown above evaluates the proposed route for turbulence aloft and color codes the EDR thresholds based on the aircraft weight class from the table above. That is, if you have the aircraft maximum takeoff weight set as a “light” aircraft, green colors on the profile represent EDR values from 13 to 15, tan are values from 16 to 35, red are values from 36 to 63, and dark red are values from 64 to 100. This provides a categorical turbulence forecast for light, moderate, severe, and extreme turbulence, respectively. Any point without a green, tan, red, or dark red color is an EDR value of 12 or less indicating it should be a relatively smooth ride.    

• READ MORE: Do I Need To Learn How To Refuel My Airplane? 

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The post What Is Turbulence? appeared first on FLYING Magazine.

Unseen—for the most part, unless rendered visible by dust or contrails—and always unwelcome, wake turbulence causes flight-path disruption at best, and fatal accidents when encountered at its worst. Pilots do what they can to avoid it, especially when on takeoff or landing, and controllers are tasked with helping us to steer clear. Still, we’re not always successful, and the price is paid in bent metal and lives lost.

One of the ongoing issues with avoiding wake turbulence lies in the complex models required to map it and predict it. Simulations currently in use by aerospace engineers developing aircraft can only capture and paint a portion of the collision of vortices that makes up a wake turbulence encounter—and they take a lot of time processing the data using supercomputers.

“Aircraft in extreme conditions cannot rely on simple modeling,” said Carlo Scalo, a Purdue University associate professor of mechanical engineering with a courtesy appointment in aeronautics and astronautics, in a recent press release from the university. “Just to troubleshoot some of these calculations can take running them on a thousand processors for a month. You need faster computation to do aircraft design.”

Scalo’s team at Purdue has developed successful models to “simulate vortex flow phenomena,” but now they require only one tenth to one hundredth of the computing power in order to use the models to simulate the vortex collision. The researchers call the model a “Coherent-vorticity-Preserving (CvP) Large-Eddy Simulation (LES).” According to the release, the development of the model has been published in a paper in the Journal of Fluid Mechanics.

“The CvP-LES model is capable of capturing super complex physics without having to wait a month on a supercomputer because it already incorporates knowledge of the physics that extreme-scale computations would have to meticulously reproduce,” Scalo said.

Researchers on the team applied the CvP-LES model to the “collision events of two vortex tubes called trefoil knotted vortices,” which are understood to trail behind an airplane’s wings and “dance when they reconnect,” stated the release. “When vortices collide, there’s a clash that creates a lot of turbulence. It’s very hard computationally to simulate because you have an intense localized event that happens between two structures that look pretty innocent and uneventful until they collide,” Scalo added.

A variety of applications are possible for the improved modeling. “The thing that’s really clever about Dr. Scalo’s approach is that it uses information about the flow physics to decide the best tactic for computing the flow physics,” said Matthew Munson, program manager for Fluid Dynamics at the Army Research Office, part of the US Army Combat Capabilities Development Command’s Army Research Laboratory. “It’s a smart strategy because it makes the solution method applicable to a wider variety of regimes than many other approaches. There is enormous potential for this to have a real impact on the design of vehicle platforms and weapons systems that will allow our soldiers to successfully accomplish their missions.”

And perhaps it may just help engineers design future aircraft that don’t create the hazardous wake turbulence we work so hard to avoid. You can watch a video of the model here.

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