fuckyeahphysica:

A vortex portal to another universe.

This is known as wingtip vortex. It is a ramification of the design of the wing and how it works.

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How does an aircraft fly? Think of it like this, due to the design of the wing, larger number of air molecules are hitting the bottom portion of the aircraft than the top.

As a result, a upward force acts on the wing, hence the wing lifts!

image

This works fine till we get to the wing tips.

In the wingtip, the air from a higher pressure wants to move to the region of lower pressure. And as a result, this forms vortices ( fancy name for the swirling motion of air ) known as Wingtip Vortex. ( because its formed in the wing tips!!! )

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Why do birds fly in a V formation?

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Migratory birds take advantage of each other’s wingtip vortices by flying in a V formation so that all but the leader are flying in the upwash from the wing of the bird ahead. ( Look at the image, each one is exactly out of phase in its wing motion ).

This upwash makes it easier for the bird to support its own weight, reducing fatigue on migration flight.

And somehow birds know about this and recalibrate themselves in flight?

Wow! There is so much more to a bird’s flight that that meets the eye. I will take up the same sometime down the line. But, If you are really curious to find out why, read this nature article.

Have a Good Day!

PC: John Benson, boldmethod,mathcareer, natgeo, NASA.

EDIT – Also do check out the Smoke Angels.

Now we now know about stalls, boundary layers, vortex generators and wing tip vortices. In the concluding post of this mini series we will try to apply the knowledge gathered thusfar in the context of a F1 car. Stay tuned…

fuckyeahphysica:

The Physics of the ‘Stall’

The proposition that more the angle of attack, more the lift does not hold at all angles.

image

At about 14 degrees, something weird happens and the aircraft instead of soaring the skies starts to plummet to the ground.

When this happens it is known as a stall.

image

                                                  Source

What causes Lift ?

The main thing to know is that a difference in pressure across the
wing–low pressure over the top and higher pressure below–creates the net
upward force we call lift.

image

Upon reaching a certain velocity, the aircraft’s lift is more than its weight and as a result, the aircraft takes off .

image

The Concept of a Boundary Layer (BL)

There is a high chance that you might have heard this word even in a casual conversation about wings and that’s because its an important concept in the context of aerodynamics and associated fields.

To understand the physics of a stall, lets consider the interaction of a moving air on a flat plate.

image

The nature of airflow over a wing/plate is the result of stickiness or viscosity of air. 

The first layer sticks to the wing/plate not moving at all.

The second layer in frictional contact with the first moves slowly over it.

And the third layer moves somewhat faster than the second

Thus layer by later the flow builds up to the free stream velocity or airspeed. These layers of flow are known as boundary layers.

image

What happens to the BL during a stall?

image

                                              Source Video

During a stall, these successive tiers of air that form the boundary layer lose their gripping on the surface and break away into turbulence.

( what i mean by turbulence is the chaotic wiggling of the test leads attached to the wing in the animation )

image

                                                  Source

It takes a pressure difference between the top and bottom parts of the wing in order to produce lift. But when the flow of air becomes turbulent ( i.e during a stall ), this pressure difference is no longer established.

As a result of which, the lift drastically decreases and the aircraft starts dropping to the ground.

How to get out of a stall ?

Stalls can cause problems only when the pilot is not aware that the aircraft is stalling. ( Unlikely but has caused accidents in yester times )

image

                                                 Source

As the airplane loses altitude, its nose dips down and airspeed picks up quickly. This restores the lift and the pilot would be able to regain control and bring the aero-plane into level flight.

How are stalls detected ?

On light aircraft there is a reed (much like used on a musical wind
instrument) mounted on one wing root, which is angled such that at the
Angle of Attack which would cause a stall, the reed “plays” which can be
heard in the cockpit.

image

Here is a view of where this system is mounted on a Cessna

On some aircrafts, it is a similar principal, however instead of a
reed, it uses a fin which at critical AoA pushes a micro-switch which
activates a buzzer/horn inside the cockpit.

image

Here is the assembly on a Beech 18


Large commercial aircraft typically rely on either Angle of Attack (AoA) Vanes or Differential Pitot Tubes  to supply input to flight computers for the purpose of calculating AoA.

image

                                                     Source


Review:

A lot of important stuff regarding aerodynamics in this post. Here’s a summary of the post:

Boundary Layer concept  — >  Why do aircrafts stall ? — >  How to get out of one  — > How are stalls detected ?

That’s all folks!

image

Hope you enjoyed today’s post and learnt something new.

Have a good one !

This post covers the fundamental principles from which the subsequent posts queued up for this weekend are derived from. Stay tuned.. It is gonna be wild ride.

On Taj Mahal and Lift in airplanes

This is an interesting story that is probably popular among those in the aerospace community on how flaps help provide lift.

image

During the World War II, a C-87 cargo plane (pic above) was all set to take off from Agra airport, India. The pilot had specifically asked for a small load of fuel for takeoff.

(because the C-87 did not climb well when heavily loaded  )

But the ground crew accidentally filled it to its full capacity and  forgot to tell the pilot about it.

image

The pilot realized this only halfway through the runway and was already committed for take off.

With a three ton overload on the plane, the plane was heading for a fatal crash with one of the towers of the Taj Mahal which was being repaired at that time and was swarming with workmen.

image

The pilot gave full throttle but it still refused to rise up.

And in a desperate attempt, he lowered the flaps fully and instantaneously the plane ballooned upwards.

image

Surely, it lost some of its forward speed due to the increased drag. But it comfortably cleared the famous tomb, averting an impending disaster. So yeah, flaps on an airplane are no joke.

Have a great one!

* Why does lowering flaps increase lift?

** Physics of stall

*** Stories are great at linking words with experience. And this aids a lot in the learning process.

image

One of the many ways to get a plane airborne is to blow fast moving air along the wings, generating lift. The above clipping is the scenario in action during a violent storm.

And surprisingly this method of moving the medium of traverse ( air ) instead of the object itself is the principle of operation of Wind Tunnels.

What is a wind tunnel ?

They are tube shaped facilities where powerful fans move air through the tube. The object is placed ( bolstered ) in a test section and the speeds of the air blown are controlled by fans 

image

By moving air around an object, the wind tunnel simulates the conditions during operation.

The object can be a
smaller-scale model of a vehicle, one piece of a vehicle, a full-size
aircraft or spacecraft, or even a common object like a tennis ball.

image

              NASA Tests Boeing Aircraft Tail in World’s Largest Wind Tunnel
 

Usually, the object carries special instruments to measure the forces
produced by the air on the object.

Engineers also study how the air
moves around the object by injecting smoke or dye into the tunnel and
photographing its motion around the object. Improving the flow of air
around an object can increase its lift and decrease its drag.

image

It saves a lot of time and money required for the testing and analysis of designs, and prototypes.


I leave you guys with this clipping from a wind tunnel testing facility at NASA:

image

The Flappy Plane : This phenomenon is known as Flutter in Aerodynamics. It is an unstable oscillation that can lead to destruction


Have a Great Day!

More about Wind Tunnels: NASA, explainthatstuff

fuckyeahphysica:

The Physics of the ‘Stall’

The proposition that more the angle of attack, more the lift does not hold at all angles.

image

At about 14 degrees, something weird happens and the aircraft instead of soaring the skies starts to plummet to the ground.

When this happens it is known as a stall.

image

                                                  Source

What causes Lift ?

The main thing to know is that a difference in pressure across the
wing–low pressure over the top and higher pressure below–creates the net
upward force we call lift.

image

Upon reaching a certain velocity, the aircraft’s lift is more than its weight and as a result, the aircraft takes off .

image

The Concept of a Boundary Layer (BL)

There is a high chance that you might have heard this word even in a casual conversation about wings and that’s because its an important concept in the context of aerodynamics and associated fields.

To understand the physics of a stall, lets consider the interaction of a moving air on a flat plate.

image

The nature of airflow over a wing/plate is the result of stickiness or viscosity of air. 

The first layer sticks to the wing/plate not moving at all.

The second layer in frictional contact with the first moves slowly over it.

And the third layer moves somewhat faster than the second

Thus layer by later the flow builds up to the free stream velocity or airspeed. These layers of flow are known as boundary layers.

image

What happens to the BL during a stall?

image

                                              Source Video

During a stall, these successive tiers of air that form the boundary layer lose their gripping on the surface and break away into turbulence.

( what i mean by turbulence is the chaotic wiggling of the test leads attached to the wing in the animation )

image

                                                  Source

It takes a pressure difference between the top and bottom parts of the wing in order to produce lift. But when the flow of air becomes turbulent ( i.e during a stall ), this pressure difference is no longer established.

As a result of which, the lift drastically decreases and the aircraft starts dropping to the ground.

How to get out of a stall ?

Stalls can cause problems only when the pilot is not aware that the aircraft is stalling. ( Unlikely but has caused accidents in yester times )

image

                                                 Source

As the airplane loses altitude, its nose dips down and airspeed picks up quickly. This restores the lift and the pilot would be able to regain control and bring the aero-plane into level flight.

How are stalls detected ?

On light aircraft there is a reed (much like used on a musical wind
instrument) mounted on one wing root, which is angled such that at the
Angle of Attack which would cause a stall, the reed “plays” which can be
heard in the cockpit.

image

Here is a view of where this system is mounted on a Cessna

On some aircrafts, it is a similar principal, however instead of a
reed, it uses a fin which at critical AoA pushes a micro-switch which
activates a buzzer/horn inside the cockpit.

image

Here is the assembly on a Beech 18


Large commercial aircraft typically rely on either Angle of Attack (AoA) Vanes or Differential Pitot Tubes  to supply input to flight computers for the purpose of calculating AoA.

image

                                                     Source


Review:

A lot of important stuff regarding aerodynamics in this post. Here’s a summary of the post:

Boundary Layer concept  — >  Why do aircrafts stall ? — >  How to get out of one  — > How are stalls detected ?

That’s all folks!

image

Hope you enjoyed today’s post and learnt something new.

Have a good one !

The Bernoulli Family.

Bernoulli’s principle, Bernoulli’s number, Bernoulli’s polynomial, Bernoulli’s differential equation and the list goes on.

If you were like me and thought that Bernoulli was the name of a single guy, you are soo wrong. They were a family !

Over the course of three generations, the Bernoullis produced eight mathematically gifted academics who, between them, contributed to the foundations of applied mathematics and physics. 

Some of the most popular ones of the family are:

1. Daniel Bernoulli ( Inventor of the Bernoulli’s equation )

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2. Jacob Bernoulli. ( The Bernoulli Numbers )

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3. Johann Bernoulli. ( One of the early adopters of Infinitesimal Calculus).

image

And the rest contributed extensively to the fields of math and physics.

If you are want to know more about the history of the Bernoulli Family click here.