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BSAeE 3-2 > AEROLAB MODULE NO. 3 > Flashcards

AEROLAB MODULE NO. 3 Flashcards

1
Q

In aeronautical applications, the
measurement of ____________ in a wind
tunnel, forces and momentums, is a very
difficult task due to the required accuracy.
The wind tunnel balances, comprised by
several hardware and software components,
provides directly the pursued measurements,
with high accuracy and reliability

A

aerodynamic loads

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2
Q

In aeronautical applications, the
measurement of aerodynamic loads in a wind
tunnel, forces and momentums, is a very
difficult task due to the required accuracy.
The _______________, comprised by
several hardware and software components,
provides directly the pursued measurements,
with high accuracy and reliability

A

wind tunnel balances

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3
Q

In aeronautical applications, the
measurement of aerodynamic loads in a wind
tunnel, forces and momentums, is a very
difficult task due to the required accuracy.
The wind tunnel balances, comprised by
_________________________,
provides directly the pursued measurements,
with high accuracy and reliability

A

several hardware and software components

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4
Q

What comprises of a Six-Component Balance?

A

Drag, Lift, Side Force, (Pitching, Yawing, Rolling) Moment

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5
Q

What comprises a three component balance?

A

Lift, Drag, Pitching

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6
Q

What comprises a two component balance?

A

Lift and Drag only

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7
Q

A wind tunnel balance is an incredibly
complicated device and its design and
construction are much better left to _______________________.

A

left to engineers of balancing than to engineers
of tunnels.

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8
Q

They are placed outside
the model, inside or
outside the wind tunnel
chamber test section, but
they always introduce some
interference in the wind flow.

A

External Balance

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9
Q

They are placed inside the
model; thus, no or little interferences
are introduced in the wind
flow by the balance
components, but a mechanical
support for the model is
always needed to maintain it
in the test chamber and change
the model orientation if desired.

A

Internal Balance

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10
Q

Types of Model Mounts

A

External: Two strut, Three strut
Internal: Single Strut, Sting

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11
Q

Any wind tunnel balance is of necessity a
compromise between the ____________________ and the
____________________.

A

required maximum load capability of all components;
accuracy required for minimum loads

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12
Q

For an internal balance, the solution to this
problem is much easier, as many balances can be
planned and installed for various load ranges, and
one chosen for the desired loads.

A danger with an inner balance is that the loads of the model can ___________________.

This can lead to a ____________.

A

unintentionally exceed the ability of the balance;
faulty balance

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13
Q

For an external balance it is important to use a
___________ to try to account for and form of
model and test for which the balance will be used
over a number of years.

A

thorough analysis

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14
Q

The estimated loads a balance has to bear are
primarily a feature of the ________________________.

A

size and speed of the tunnel test section

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15
Q

If a tunnel size is doubled, the size of the
platform and the loads are increased ________ for a
set vehicle-to-tunnel-size ratio, platform attitude
and tunnel speed.

A

fourfold

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16
Q

In general usage _____ types of external
balances were used. These balances are
named for their main load-carrying members _________________.

A

four ; wire, frame, yokes and pyramid

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17
Q

Four External Balances

A

Wire type, Platform, Yoke, Pyramid Balance

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18
Q

The model was usually mounted inverted so that the
aerodynamic lift applied to the weight to prevent
the wires from being removed, as the resulting
stress can never be reduced to zero.

A

Wire Balance

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19
Q

Wire Balances

There’s a strong ______ on the wires that was
hard to accurately determine. The wires appeared to
split, which would result in the ______.

A

tare drag ; model losing

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20
Q

Wire balances turned out to be much __________ than the alternatives and since the very
early days of aeronautics have not been used
extensively.

A

less stable and flexible

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21
Q

Wire Balances

The space occupied is very __________

A

large

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22
Q

Platform, Yoke, and Pyramid Balances

These balances provide
mechanisms for changing the
_______________ and
transmit the _________ down
into a system of linkages
that separate them into force
and moment components.

A

angle of attack and yaw ; model loads

23
Q

Platform, Yoke, and Pyramid Balances

For Linkage type, the strut being
rigid, minimizes ___________.

A

deflection

24
Q

Platform, Yoke, and Pyramid Balances

By choosing __________,
interaction loads can be reduced to
a small value.

A

proper linkages

25
Q

Platform, Yoke, and Pyramid Balances

__________ can be encounter in high speed flows.

A

Deflections

26
Q

Platform, Yoke, and Pyramid Balances

Is it suitable for large test section tunnels? Yes, No or Maybe?

A

It is not

27
Q

Platform, Yoke, and Pyramid Balances

_________ drag is more when three point strut support is exhibited.

A

Interference

28
Q

External Balances

The linkage system by which the force and moment components are separated have gradually worked into three different fundamental types what are those?

A

Platform, Yoke, Pyramidal

29
Q

One of the most troublesome problems of wind tunnel balances is the ____________.

A

lack of rigidity

30
Q

____________ in the balance may move the model from the resolving center and invalidate the moment data or nullify the balance alignment so that part of the lift appears as drag or side force.

A

Deflections

31
Q

Deflections must be _________ to where they are negligible or they must be evaluated and accounted for in the data reduction process.

A

kept down

32
Q

What is the greatest source of deflection?

A

The mounting mechanism

33
Q

Deflections must be long in reaching out of the test section and thin to prevent _____________.

A

overinterference

34
Q

The only way that the wind tunnel engineer can solve deflection is to use ___________ materials for the strut. By having a deep and stable structure, deflections in the balance frame can be reduced

A

high-modulus elasticity

35
Q

Balance linkages and Pivots

A large number of levers are the main components of an external balance and are built to have minimal ________ under high load. That increases their ________ and also increases their ________.

A

deflection ; weight ; height

36
Q

Balance linkages and Pivots

Usually, the joints between the levers are ________ with very limited _______

A

Pivots ; angular motion

37
Q

Early pivots were _______ in wind tunnel
balances. Because the edges
of this can be damaged
by shock loads and can bear
loads only in a compressive
direction, they have been
replaced by flexure pivot.

A

knife
edges

38
Q

The benefits of ________ include:
1. They may be designed to withstand loads between
the coupled members in either direction with no
loss of motion.
2. They are practically frictionless and thus reduce
the symptoms of hysteresis.
3. They can survive treatment which is relatively
harsh.
4. They are practically wearproof; therefore they
remain constant for an infinite period of time.

A

flexures

39
Q

For external balance calibration, calibration takes at least ________ for a professional crew to calibrate the new balance.

A

3 months

40
Q

__________ involves loading the balance components
to see if they read what they should, testing the
system deflection, calculating the natural frequency
of the balance in order to prevent resonance, and
applying fluctuating load.

A

Calibration

41
Q

Transducer of Internal Balance

A

Strain Gauges, Piezoelectric devices

42
Q

These balances are normally supplied to the customer
already calibrated and with the acquisition system.

A

Internal Balance

43
Q

The _____________ is compounded by
several items that allow the conversion of physical
forces into digital values that can be managed by a
computer. Several components comprise this and the selection of their properties will have an important
impact on the system behavior.

A

data acquisition system (DAQ)

44
Q

Of these two, strain gages far ________
piezoelectric devices.

The reason for this is that
although piezoelectric devices are extremely stiff
and have outstanding frequency response, they do
not measure steady loads well.

A

outnumber

45
Q

disadvantage of piezoelectric devices

A

extremely stiff, have high outstanding frequency response and does not measure steady loads well.

46
Q

In practice, the terms internal balance and internal strain gage balance are effectively ______

A

Synonimous

47
Q

The calibration method serves various purposes
including:

A
  1. Loading the balance to show
  2. Determining the coefficients of equilibrium
  3. Defining deflections as load feature
  4. To check the repeatability over short periods of
    time
  5. Tests reliability for longer periods of time
  6. Defines sensitivity or minimum response load
  7. To detect hysteresis
48
Q

The calibrations require a rather elaborate
__________. The system provides capability for
the balance to be rotated through 360deg and pitched
in the vertical plane.

A

calibration rig

49
Q

The __________ is used to keep the applied
load system aligned to the model attachment portion
of the balance, just as the model will be when the
system is loaded in the tunnel.

A

pitching motion

50
Q

This means the model attachment portion is kept
horizontal for all loading conditions since this
system uses weights and gravity to apply the loads.
It also allows the _______________ to
be measured.

A

balance and sting deflection

51
Q

__________ are used to apply the loads. These are indexed so that various values of moments
can be applied while holding the normal or side
force constant.

A

Calibration bars

52
Q

When the model is attached to the balance, the
orientation of the loads applied to the balance has
to be positively and precisely associated with the
model orientation.

This alignment is typically done
by ____________ rather than by some
adjustment device, so that the precision of
reproducibility is close to the limits of the
machine tool.

A

pins, buttons, or splines

53
Q

The calibration bar is leveled to _______. As
loads are applied at each loading station the bar
is again leveled and the sting and calibration bar
deflection is reported along with the outputs of
the balance. The measures are of deflection. Used
during test to correct the indicated angles of
attack.

A

zero load

54
Q

In order to get the ____________ and
estimate their reliability a large number of load
combinations are needed.

The time required to do a
full calibration of the six-component balance with
manually applied loads runs into weeks, involving
many people.

A

balance coefficients

BSAeE 3-2 (33 decks)

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