A wind tunnel (风洞) is used for teasing planes or plane
models. In a wind tunnel air is blown over a plane or a model
placed in a test section(区).Wind tunnel test sections are
different in size depending on airflow speed requirements.
Some low-speed tunnels have test sections large enough for a
complete small plane. In the very high speed tunnels used for
space testing, however, the model may be as small as a pencil.
There are two ways of feeding air to the test section. In
the constant flow tunnel, airflow is produced by electric
fans. It is forced through the tunnel to the test section,
then through another tunnel section back to the starting point
for reuse.
The other way involves (卷入) storing high-pressure air in a
box, sending it out by a controlling device(装置) to pass
through the tunnel and test section into another box. This way
is usually used for a very short period of high-speed airflow.
Wind tunnels are usually used to test planes before they are
flown. Problems in a plane can be found when it meets the
high-speed airflow in the tunnel. For example, if the wings
are built so that they would weaken(become weak) at high
speeds, this fact can be discovered in the tunnel, saving many
lives and millions of dollars.
In a wind tunnel, scientists also find out how different
planes will act different speeds. They find out such things as
how the air dives by the wing surfaces, how slowly a plane can
fly before it starts to drop, and how fast it can climb.
52.Some wind tunnel sections are larger than others because
________.
A. they are used large planes B. stronger wind can be
produced in them
C. they are built to meet a higher speed test D. the wind used
in them flows at a lower speed
53.Which of the following shows the right way of feeding air
to a wind tunnel section usually
used for a high speed test?
( ← = wind flow = test section)
54. "This fact" in paragraph 4 of the text refers to _______.
A. the wing are not good enough B. it costs a lot to test a
plane
C. some problems are found with the plane D. many people will
die in a plane accident
55. A wind tunnel can be used to find out ______.
A. how fast a plane can rise B. how smooth a plane's
surface is
C. if a plane can land in a very strong wind D. if a plane
will drop when flying at a low height
参考答案：
DDAA