#windtunneltesting — Public Fediverse posts

Making Quieter Shock Waves

NASA’s X-59 aircraft is intended to demonstrate supersonic flight without the boom. Although it’s broken into supersonic speeds, we haven’t yet heard its “sonic thump” because, so far, it’s been accompanied by conventional supersonic aircraft, which are louder.

The idea behind the long, skinny X-59 is to create weaker, widely-spaced shocks along the aircraft body. Weaker shocks are easier for atmospheric effects to damp out before they reach the ground, and spacing them out makes it harder for them to “pile up” at the nose and tail to create the strong double shocks that merge into a sonic boom.

NASA is preparing to test the X-59’s in-flight shocks soon, including with in-air schlieren photography like they’ve done in the past for other aircraft. But we’ve already have a glimpse of what to expect, thanks to wind tunnel testing, shown above. Ignore the three dark diagonal lines in the middle of the image (those are from the wind tunnel, not the model aircraft), and focus instead on the thin bright lines coming off the plane. Those are some impressively subtle shock waves!

Hear more from the aircraft’s designer and test pilots in this Ars Technica article. (Image credit: NASA; see also: Ars Technica, M. Ahaus et al.)

Making Quieter Shock Waves

NASA’s X-59 aircraft is intended to demonstrate supersonic flight without the boom. Although it’s broken into supersonic speeds, we haven’t yet heard its “sonic thump” because, so far, it’s been accompanied by conventional supersonic aircraft, which are louder.

The idea behind the long, skinny X-59 is to create weaker, widely-spaced shocks along the aircraft body. Weaker shocks are easier for atmospheric effects to damp out before they reach the ground, and spacing them out makes it harder for them to “pile up” at the nose and tail to create the strong double shocks that merge into a sonic boom.

NASA is preparing to test the X-59’s in-flight shocks soon, including with in-air schlieren photography like they’ve done in the past for other aircraft. But we’ve already have a glimpse of what to expect, thanks to wind tunnel testing, shown above. Ignore the three dark diagonal lines in the middle of the image (those are from the wind tunnel, not the model aircraft), and focus instead on the thin bright lines coming off the plane. Those are some impressively subtle shock waves!

Hear more from the aircraft’s designer and test pilots in this Ars Technica article. (Image credit: NASA; see also: Ars Technica, M. Ahaus et al.)

Derecho-Induced Skyscraper Damage

Derechos are short-lived, intense wind storms sometimes associated with thunderstorms. Last spring, such a storm passed through Houston, leaving downtown skyscrapers with more damage than a hurricane with comparable wind speeds. Now researchers believe they know why a derecho’s 40 meter per second winds can badly damage buildings built to withstand 67 meter per second hurricane winds.

In surveying the damage to Houston’s skyscrapers, the team noted that broken windows were concentrated in areas that faced other tall buildings. In a wind facility, the team explored how skyscrapers interfered with each other, based on their separation difference. They looked both at conditions that mimicked a hurricane’s winds as well as the downbursts — strong downward wind bursts — that are found in derechos.

The researchers found that downbursts in between nearby buildings caused extremely strong suction forces along a building’s face — even compared to the forces seen with higher hurricane-force winds. Currently, these buildings are designed for hurricane-like conditions, but the team suggests that — at least in some regions — designers will need to take into account how downburst wind patterns affect a skyscraper, too. (Image credit: National Weather Service; research credit: O. Metwally et al.; via Ars Technica)

#derecho #downburst #engineering #fluidDynamics #meteorology #physics #science #wind #windTunnelTesting

Derecho-Induced Skyscraper Damage

Derechos are short-lived, intense wind storms sometimes associated with thunderstorms. Last spring, such a storm passed through Houston, leaving downtown skyscrapers with more damage than a hurricane with comparable wind speeds. Now researchers believe they know why a derecho’s 40 meter per second winds can badly damage buildings built to withstand 67 meter per second hurricane winds.

In surveying the damage to Houston’s skyscrapers, the team noted that broken windows were concentrated in areas that faced other tall buildings. In a wind facility, the team explored how skyscrapers interfered with each other, based on their separation difference. They looked both at conditions that mimicked a hurricane’s winds as well as the downbursts — strong downward wind bursts — that are found in derechos.

The researchers found that downbursts in between nearby buildings caused extremely strong suction forces along a building’s face — even compared to the forces seen with higher hurricane-force winds. Currently, these buildings are designed for hurricane-like conditions, but the team suggests that — at least in some regions — designers will need to take into account how downburst wind patterns affect a skyscraper, too. (Image credit: National Weather Service; research credit: O. Metwally et al.; via Ars Technica)

#derecho #downburst #engineering #fluidDynamics #meteorology #physics #science #wind #windTunnelTesting

Derecho-Induced Skyscraper Damage

Derechos are short-lived, intense wind storms sometimes associated with thunderstorms. Last spring, such a storm passed through Houston, leaving downtown skyscrapers with more damage than a hurricane with comparable wind speeds. Now researchers believe they know why a derecho’s 40 meter per second winds can badly damage buildings built to withstand 67 meter per second hurricane winds.

In surveying the damage to Houston’s skyscrapers, the team noted that broken windows were concentrated in areas that faced other tall buildings. In a wind facility, the team explored how skyscrapers interfered with each other, based on their separation difference. They looked both at conditions that mimicked a hurricane’s winds as well as the downbursts — strong downward wind bursts — that are found in derechos.

The researchers found that downbursts in between nearby buildings caused extremely strong suction forces along a building’s face — even compared to the forces seen with higher hurricane-force winds. Currently, these buildings are designed for hurricane-like conditions, but the team suggests that — at least in some regions — designers will need to take into account how downburst wind patterns affect a skyscraper, too. (Image credit: National Weather Service; research credit: O. Metwally et al.; via Ars Technica)

#derecho #downburst #engineering #fluidDynamics #meteorology #physics #science #wind #windTunnelTesting

Derecho-Induced Skyscraper Damage

Derechos are short-lived, intense wind storms sometimes associated with thunderstorms. Last spring, such a storm passed through Houston, leaving downtown skyscrapers with more damage than a hurricane with comparable wind speeds. Now researchers believe they know why a derecho’s 40 meter per second winds can badly damage buildings built to withstand 67 meter per second hurricane winds.

In surveying the damage to Houston’s skyscrapers, the team noted that broken windows were concentrated in areas that faced other tall buildings. In a wind facility, the team explored how skyscrapers interfered with each other, based on their separation difference. They looked both at conditions that mimicked a hurricane’s winds as well as the downbursts — strong downward wind bursts — that are found in derechos.

The researchers found that downbursts in between nearby buildings caused extremely strong suction forces along a building’s face — even compared to the forces seen with higher hurricane-force winds. Currently, these buildings are designed for hurricane-like conditions, but the team suggests that — at least in some regions — designers will need to take into account how downburst wind patterns affect a skyscraper, too. (Image credit: National Weather Service; research credit: O. Metwally et al.; via Ars Technica)

#derecho #downburst #engineering #fluidDynamics #meteorology #physics #science #wind #windTunnelTesting

Derecho-Induced Skyscraper Damage

Derechos are short-lived, intense wind storms sometimes associated with thunderstorms. Last spring, such a storm passed through Houston, leaving downtown skyscrapers with more damage than a hurricane with comparable wind speeds. Now researchers believe they know why a derecho’s 40 meter per second winds can badly damage buildings built to withstand 67 meter per second hurricane winds.

In surveying the damage to Houston’s skyscrapers, the team noted that broken windows were concentrated in areas that faced other tall buildings. In a wind facility, the team explored how skyscrapers interfered with each other, based on their separation difference. They looked both at conditions that mimicked a hurricane’s winds as well as the downbursts — strong downward wind bursts — that are found in derechos.

The researchers found that downbursts in between nearby buildings caused extremely strong suction forces along a building’s face — even compared to the forces seen with higher hurricane-force winds. Currently, these buildings are designed for hurricane-like conditions, but the team suggests that — at least in some regions — designers will need to take into account how downburst wind patterns affect a skyscraper, too. (Image credit: National Weather Service; research credit: O. Metwally et al.; via Ars Technica)

#derecho #downburst #engineering #fluidDynamics #meteorology #physics #science #wind #windTunnelTesting

Wind plays a major role in cycling, since aerodynamic drag is the greatest force hampering a cyclist. In road racing, both individual cyclists and teams use tactics that vary based on the wind speed and direction. Crosswinds — when the apparent wind comes from the side in the cyclist’s point of view — are some of the toughest conditions to deal with. In races, groups will often form echelons to minimize the group’s overall effort in a crosswind. Alternatively, racers looking to tire their competitors out will position themselves on the road so that the rider behind them gets little to no shelter from the wind; this is known as guttering an opponent.

In this study, researchers put a lone cyclist in a wind tunnel and measured the effects of crosswind from a pure headwind to a pure tailwind and every possible angle in between. From that variation, they were able to mathematically model the aerodynamic effects of crosswind on a cyclist from every angle. With rolling resistance (a cyclist’s second largest opposing force) included, they found relatively few conditions where a crosswind actually helped a cyclist. Most of the time — as any cyclist can tell you — hiding from the wind is beneficial. (Image credit: J. Dylag; research credit: C. Clanet et al.)

Related topics: The physics of the Tour de France, how the peloton protects riders aerodynamically, track cycling physics, and a look inside wind tunnel testing bikes and cyclists

Catch all of our ongoing Olympics coverage here.

https://fyfluiddynamics.com/2024/08/paris-2024-cycling-in-crosswinds/

#crosswinds #cycling #drag #dragReduction #echelon #fluidDynamics #olympics #Paris2024 #physics #science #sports #windTunnelTesting