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Questions and Answers
How is absolute pressure in the tunnel determined?
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?
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?
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?
In a wind tunnel, when is the local static pressure typically equal to tunnel static pressure?
What will be observed in a wind tunnel when there is increased velocity and reduced cross-sectional area?
What will be observed in a wind tunnel when there is increased velocity and reduced cross-sectional area?
What can be inferred about the total pressure in free stream conditions?
What can be inferred about the total pressure in free stream conditions?
What is the size of the working section in the described wind tunnel?
What is the size of the working section in the described wind tunnel?
Which type of pressure reading will be higher when using a Pitot Static tube?
Which type of pressure reading will be higher when using a Pitot Static tube?
What is the primary function of the fan in the wind tunnel system?
What is the primary function of the fan in the wind tunnel system?
Which component directly connects to the static pressure tapping at the rear of the working section?
Which component directly connects to the static pressure tapping at the rear of the working section?
What is the significance of the honeycomb type flow straightener in the wind tunnel?
What is the significance of the honeycomb type flow straightener in the wind tunnel?
What happens to static pressure inside the working section when the fan operates?
What happens to static pressure inside the working section when the fan operates?
What is the ratio of the contraction section used in the wind tunnel?
What is the ratio of the contraction section used in the wind tunnel?
How does the inclined manometer measure changes in air velocity?
How does the inclined manometer measure changes in air velocity?
What role does the electrical console play in the wind tunnel system?
What role does the electrical console play in the wind tunnel system?
What happens to the inclined manometer readings at atmospheric pressure?
What happens to the inclined manometer readings at atmospheric pressure?
What is the primary function of the inclined manometer bank in the context of a wind tunnel?
What is the primary function of the inclined manometer bank in the context of a wind tunnel?
How are water levels preserved in the manometer tubes during operational changes?
How are water levels preserved in the manometer tubes during operational changes?
What are the quick release connectors used for in the inclined manometer system?
What are the quick release connectors used for in the inclined manometer system?
What effect does raising or lowering the displacer in the water reservoir have on the manometer readings?
What effect does raising or lowering the displacer in the water reservoir have on the manometer readings?
What is the orientation of the manometer tubes in the inclined manometer bank?
What is the orientation of the manometer tubes in the inclined manometer bank?
What is the operational range of the inclined manometer in terms of pressure measurement?
What is the operational range of the inclined manometer in terms of pressure measurement?
What do the cursors help reduce when taking measurements?
What do the cursors help reduce when taking measurements?
Where is the inclined manometer typically installed within the wind tunnel setup?
Where is the inclined manometer typically installed within the wind tunnel setup?
What is the purpose of the blanking plug in the wind tunnel?
What is the purpose of the blanking plug in the wind tunnel?
What is a potential risk of not securing a model before starting the wind tunnel fan?
What is a potential risk of not securing a model before starting the wind tunnel fan?
How does the twine aid in flow visualization?
How does the twine aid in flow visualization?
Where can the stainless steel 'L' shaped tube for twine be positioned?
Where can the stainless steel 'L' shaped tube for twine be positioned?
What must be done before operating the wind tunnel fan with the twine?
What must be done before operating the wind tunnel fan with the twine?
Which of the following is NOT a function of the manometer bank?
Which of the following is NOT a function of the manometer bank?
What does the protective grill around the fan primarily ensure?
What does the protective grill around the fan primarily ensure?
Which manometer options are available for use with some models?
Which manometer options are available for use with some models?
What allows the measurement of static pressure when using the Bernoulli Apparatus?
What allows the measurement of static pressure when using the Bernoulli Apparatus?
How is the equipment controlled from a PC in the wind tunnel?
How is the equipment controlled from a PC in the wind tunnel?
What is the purpose of the circular hatch in the wind tunnel?
What is the purpose of the circular hatch in the wind tunnel?
What feature of the standard hatch cover aids in securely mounting models during flow visualization studies?
What feature of the standard hatch cover aids in securely mounting models during flow visualization studies?
What do the roof tappings in the working section enable?
What do the roof tappings in the working section enable?
How does the design of the circular opening help avoid flow disturbance?
How does the design of the circular opening help avoid flow disturbance?
What is the main purpose of the small hatch located behind the model mounting position?
What is the main purpose of the small hatch located behind the model mounting position?
Which component is used to calculate and display instantaneous air velocity?
Which component is used to calculate and display instantaneous air velocity?
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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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