Fluid Dynamics Equipment Quiz

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Questions and Answers

How is absolute pressure in the tunnel determined?

By relating the tunnel datum to the atmospheric datum and adding barometric pressure (correct)

By using only the total pressure in the tunnel

By measuring the static pressure only

By measuring the dynamic pressure only

What happens when a manometer tube is disconnected?

It shows a higher static pressure reading

It measures the dynamic pressure only

It shows atmospheric datum (correct)

It measures absolute pressure

What is the relationship between total pressure and static pressure measured with a Pitot Static tube in a wind tunnel?

Total pressure is always higher than static pressure (correct)

Total pressure is always lower than static pressure

Total pressure is both lower and higher than static pressure depending on conditions

Total pressure equals static pressure at all times

In a wind tunnel, when is the local static pressure typically equal to tunnel static pressure?

When the cross-sectional area is unchanged Signup and view all the answers

What will be observed in a wind tunnel when there is increased velocity and reduced cross-sectional area?

Sub-atmospheric pressures Signup and view all the answers

What can be inferred about the total pressure in free stream conditions?

It equals the atmospheric pressure when ignoring frictional losses Signup and view all the answers

What is the size of the working section in the described wind tunnel?

150 mm x 150 mm Signup and view all the answers

Which type of pressure reading will be higher when using a Pitot Static tube?

Static pressure tapping Signup and view all the answers

What is the primary function of the fan in the wind tunnel system?

To draw air through the working section. Signup and view all the answers

Which component directly connects to the static pressure tapping at the rear of the working section?

Inclined Manometer Signup and view all the answers

What is the significance of the honeycomb type flow straightener in the wind tunnel?

It minimizes turbulence within the tunnel. Signup and view all the answers

What happens to static pressure inside the working section when the fan operates?

It becomes sub-atmospheric. Signup and view all the answers

What is the ratio of the contraction section used in the wind tunnel?

9.4:1 Signup and view all the answers

How does the inclined manometer measure changes in air velocity?

By drawing water up relevant tubes as air velocity increases. Signup and view all the answers

What role does the electrical console play in the wind tunnel system?

It allows full electronic monitoring and recording of pressure measurements. Signup and view all the answers

What happens to the inclined manometer readings at atmospheric pressure?

All tubes will indicate the same level as the water reservoir. Signup and view all the answers

What is the primary function of the inclined manometer bank in the context of a wind tunnel?

To measure small pressure differences using water Signup and view all the answers

How are water levels preserved in the manometer tubes during operational changes?

Using a sliding cursor that locks in the reading Signup and view all the answers

What are the quick release connectors used for in the inclined manometer system?

To connect to different instruments and models quickly Signup and view all the answers

What effect does raising or lowering the displacer in the water reservoir have on the manometer readings?

It affects all connected tubes simultaneously Signup and view all the answers

What is the orientation of the manometer tubes in the inclined manometer bank?

30° inclined Signup and view all the answers

What is the operational range of the inclined manometer in terms of pressure measurement?

0 – 160 mm H2O Signup and view all the answers

What do the cursors help reduce when taking measurements?

Parallax error and calculation difficulties Signup and view all the answers

Where is the inclined manometer typically installed within the wind tunnel setup?

Inside the frame below the test section Signup and view all the answers

What is the purpose of the blanking plug in the wind tunnel?

To avoid disturbances in the working section Signup and view all the answers

What is a potential risk of not securing a model before starting the wind tunnel fan?

The model could be sucked into the fan blades Signup and view all the answers

How does the twine aid in flow visualization?

It follows the flow contour around the model Signup and view all the answers

Where can the stainless steel 'L' shaped tube for twine be positioned?

In the roof at three alternative positions Signup and view all the answers

What must be done before operating the wind tunnel fan with the twine?

The end of the twine should be tied to the 'O' ring Signup and view all the answers

Which of the following is NOT a function of the manometer bank?

Providing airflow visualization Signup and view all the answers

What does the protective grill around the fan primarily ensure?

Safety by preventing contact with rotating blades Signup and view all the answers

Which manometer options are available for use with some models?

13 tube inclined water manometer or a 16 channel electronic manometer Signup and view all the answers

What allows the measurement of static pressure when using the Bernoulli Apparatus?

The support plug Signup and view all the answers

How is the equipment controlled from a PC in the wind tunnel?

Via a USB port Signup and view all the answers

What is the purpose of the circular hatch in the wind tunnel?

To mount optional models Signup and view all the answers

What feature of the standard hatch cover aids in securely mounting models during flow visualization studies?

Central boss with a hole Signup and view all the answers

What do the roof tappings in the working section enable?

Installation of flow visualisation systems Signup and view all the answers

How does the design of the circular opening help avoid flow disturbance?

By being flush with the inside wall Signup and view all the answers

What is the main purpose of the small hatch located behind the model mounting position?

To enable downstream model installation Signup and view all the answers

Which component is used to calculate and display instantaneous air velocity?

Static pressure sensor Signup and view all the answers

Study Notes

Wind Tunnel Overview

The wind tunnel features a square working section measuring 150 mm (6”) constructed from clear acrylic for visibility.
Air is drawn into the working section by a variable speed fan located at the discharge end of the tunnel.
A honeycomb flow straightener and a 9.4:1 contraction ratio enhance airflow development in the working section.
Electronic monitoring of pressure is achieved through an electronic manometer bank integrated with Wind Tunnel software.

Airflow and Pressure Measurement

The fan generates sub-atmospheric pressure within the working section to minimize turbulence.
Static pressure inside the tunnel is typically lower than atmospheric pressure, impacting measurements recorded by instruments.
The inclined manometer connects to a common water reservoir, and tube levels indicate air velocity fluctuations as flow increases.

Wind Tunnel Components

Electrical Console allows control of the wind tunnel setup via PC interface through a USB port.
Static Pressure Sensor measures the static pressure at the rear of the working section to calculate air velocity.
Circular Hatch (120 mm diameter) enables the installation of models while maintaining flush alignment to avoid flow disturbances.
Small Hatch positioned downstream for the installation of additional models, kept covered until in use.

Flow Measurement and Visualisation

Roof Tappings provide points for flow visualization and measurements using devices like the Pitot Static tube.
Fan is equipped with a protective grill for safety during operation, and models must be secured before fan activation to prevent accidents.
Flow Visualisation System uses lightweight twine to show flow contours, indicating turbulence or boundary layer separation along models.

Manometers and Pressure Measurements

A manometer bank is essential for pressure measurement; options include a 13-tube inclined water manometer or a 16-channel electronic manometer.
The inclined manometer measures small pressure differences using water, located beside the Electrical Console for convenience.
Each tube features a sliding cursor to record water levels, facilitating easy reading and comparison of pressure measurements.

Operational Notes

The total pressure in the wind tunnel corresponds to atmospheric pressure in idle conditions, but readings differ when airflow is present.
Measurement conventions differ in the tunnel; for instance, a Pitot Static tube indicates a lower reading for total pressure compared to static pressure under airflow conditions.
Adjustments to the manometer's water level should be conducted after model changes to maintain accurate measurements.

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Description

Test your knowledge on various fluid dynamics equipment and instruments. This quiz covers essential components such as flow straighteners, static pressure sensors, and inclined manometers. Perfect for students in engineering or physics courses.