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AirPressure and Algebraic Relationships - Contenido educativo

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Subido el 28 de mayo de 2007 por EducaMadrid

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NASA Connect Segment exploring drag and agebraic relationships. The video explains flow visualization and air flow and how engineers use algebra in their work.

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Why are patterns important in determining drag? 00:00:00
What algebraic relationship shows that a car has drag? 00:00:05
Explain the relationship between pressure and glow. 00:00:09
This is one of NASA Langley's many wind tunnels. 00:00:14
It's called the Basic Aerodynamics Research Tunnel, or BART for short. 00:00:16
Engineers like me use the BART in a technique called flow visualization to try 00:00:19
to understand how the air flows around aircraft. 00:00:23
By looking at or visualizing the airflow, 00:00:26
we can help aircraft designers create new shapes 00:00:28
that are more aerodynamic and produce less drag. 00:00:30
Drag slows down a vehicle or an object, 00:00:33
as you observed in the activity you just conducted. 00:00:35
Recently, NASA Langley used its experience in testing and simulating aircraft 00:00:38
to help a car manufacturer visualize and describe the airflow over one of its automobiles. 00:00:42
What we as engineers would really like to see is the air flowing continuously from the front 00:00:48
of the car to the back of the car, like the flow over this cylinder. 00:00:52
There's no interruption in the airflow and there is no drag. 00:00:55
Unfortunately, this is not how things work in real life, 00:00:58
so we have to make airplanes and cars streamlined. 00:01:01
This particular automobile is streamlined, which means it was designed 00:01:04
to offer minimal resistance to airflow. 00:01:07
Because of its shape, this car has little drag. 00:01:09
You know, that sounds like our activity. 00:01:12
The tetrahedron had the lowest drag because of its shape. 00:01:14
That's right. 00:01:17
The shape of airplanes and cars is mainly determined by aerodynamics and safety. 00:01:18
However, a car has additional factors that may affect its shape. 00:01:22
The vehicle must look good for people to buy it, the passengers must be comfortable, 00:01:25
and the vehicle must be able to transport people, cargo, or both. 00:01:29
With this in mind, automotive engineers used geometry to design cars with one of three shapes, 00:01:33
a hatchback, a squareback, or a notchback. 00:01:38
Which of the three shapes do you think would have the highest drag? 00:01:41
Looks like the notchback has the most drag. 00:01:45
You're right. 00:01:47
After deciding on the shape to test, we created a scale model 00:01:48
of a typical passenger vehicle with a notchback design. 00:01:51
To visualize and measure the airflow around this model, we used the BART and materials 00:01:54
like kerosene and titanium dioxide, a white powdery substance used in paint. 00:01:58
Visualizing the airflow provides a picture of how the air moves around the vehicle. 00:02:03
Okay, so how do you visualize airflow? 00:02:07
You can't really see air, can you? 00:02:10
No, you can, and that's a good question. 00:02:12
Without special materials, you really can't see air flowing. 00:02:14
So we mixed titanium dioxide and kerosene together and applied it to the surface of the model. 00:02:17
We turned on the wind tunnel, and as air flowed over the model, 00:02:22
the kerosene evaporated or turned into a gas. 00:02:24
The titanium dioxide left on the surface shows us an airflow pattern. 00:02:28
This pattern tells us how the air is moving close to the surface. 00:02:31
The measurements we collect allow us to describe the air's properties in motion with numbers. 00:02:35
Luther, that looks really cool, you know, but what does this pattern say 00:02:40
about the shape of the car and the drag it produces? 00:02:43
Well, this pattern tells us that the air is actually traveling in the same direction 00:02:45
as the car, or in other words, towards the back window. 00:02:48
This is called reverse flow. 00:02:51
Reverse flow creates low pressures on the back of the vehicle, which increases drag. 00:02:53
Remember this drawing? 00:02:58
See how the air flows smoothly over the cylinder and comes together again in the back? 00:02:59
Although this isn't how things work in the real world, the air pressure in the front, 00:03:03
PF, is the same or equal to the pressure in the back, PB. 00:03:08
When the pressure in the front is equal to the pressure in the back, then there is no drag. 00:03:12
However, look at our notchback model. 00:03:16
See how the air flow separates at the back of the vehicle and the air actually begins 00:03:19
to flow in the reverse direction? 00:03:23
This is reverse flow, and the pressure in the front 00:03:24
of the model is greater than the pressure in the back. 00:03:27
When the pressure in the front is greater than the pressure in the back, you have drag. 00:03:29
Flow visualization helps us understand how the air flows over the model, 00:03:34
but in order to measure the pressures on the surface, we had to use additional techniques. 00:03:38
The most exciting is probably pressure-sensitive paint. 00:03:41
In addition to NASA Langley, NASA Glenn Research Center in Ohio, 00:03:44
and NASA Ames Research Center in California use pressure-sensitive paint 00:03:48
in their wind tunnel tests. 00:03:52
Pressure-sensitive paint, or PSP, is a special paint that glows when exposed to blue light. 00:03:54
The glow is really due to special molecules embedded in the paint called luminophores. 00:04:00
Luminophores. 00:04:05
Sounds like a word that comes from illuminate. 00:04:06
That's right. 00:04:09
These luminophores are excited or given excess energy by the blue light. 00:04:09
The luminophores don't like to have excess energy, so they get rid of it by either glowing 00:04:13
or by bumping into nearby oxygen molecules. 00:04:17
The behavior of the luminophores allows us to see a relationship between the brightness 00:04:20
of their glow and the pressure on the surface. 00:04:24
A relationship. 00:04:27
Sounds like algebra. 00:04:29
That's right. 00:04:30
I use algebra in my work every day. 00:04:31
Let me show you. 00:04:33
Remember when I said that the behavior of the luminophores allows us to relate the brightness 00:04:34
of the glow to the pressure on the surface? 00:04:37
This is done using a graph like this. 00:04:40
The curve on the graph shows an inverse relationship between pressure and glow. 00:04:42
When glow increases, we know the pressure has decreased. 00:04:46
But when glow decreases, we know the pressure has increased. 00:04:49
This inverse relationship can be represented with the following algebraic equation. 00:04:53
Pressure equals quantity glow minus one divided by the slope of the curve. 00:04:58
Using the graph in this algebraic equation, we solve for pressure. 00:05:03
The pressures we calculate can be displayed using different colors like this. 00:05:07
The red regions show where the pressures are high, and the blue regions show where the 00:05:11
pressures are low. 00:05:14
As you can see, the pressures in the front of the car are higher than the pressures in 00:05:15
the back. 00:05:19
As we calculated earlier, this difference determines the vehicle's drag. 00:05:20
This information is used by car designers to decide if the shape or geometry of a car 00:05:24
needs to be changed. 00:05:28
If I were a car designer, I'd change the notchback shape of the car. 00:05:29
It creates too much drag. 00:05:33
Well, Van, the research conducted here at the NASA Langley Research Center can be used 00:05:35
by automotive engineers and designers to create new designs and shapes with reduced drag and 00:05:39
better fuel efficiency. 00:05:44
This allows drivers like us to save money and protect the environment. 00:05:45
Okay, we've seen how different shapes affect drag. 00:05:49
Now, let's head back to First Flight Middle School and see what would happen if we changed 00:05:53
the frontal surface area of an object. 00:05:59
Are you ready, guys? 00:06:02
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Idioma/s:
en
Materias:
Matemáticas
Niveles educativos:
▼ Mostrar / ocultar niveles
      • Nivel Intermedio
Autor/es:
NASA LaRC Office of Education
Subido por:
EducaMadrid
Licencia:
Reconocimiento - No comercial - Sin obra derivada
Visualizaciones:
520
Fecha:
28 de mayo de 2007 - 16:51
Visibilidad:
Público
Enlace Relacionado:
NASAs center for distance learning
Duración:
06′ 03″
Relación de aspecto:
4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
Resolución:
480x360 píxeles
Tamaño:
36.39 MBytes

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