Fluid Mechanics Concepts

Questions and Answers

What is the primary use of an inclined tube manometer?

To measure fluid flow rates

To measure temperature variations in liquids

To measure large-scale pressure changes

To measure small changes in pressure (correct)

In terms of pressure transducers, what characterizes a gauge transducer?

It is only used for low-pressure measurements

It measures the absolute pressure only

It is open to atmospheric pressure (correct)

It measures pressure at absolute zero

Which type of pressure transducer measures the difference between two applied pressures?

Vacuum transducer

Absolute transducer

Gauge transducer

Differential transducer (correct)

What is linked to the resistance of shear forces in a fluid?

Viscosity of the fluid Signup and view all the answers

What error might a pressure transducer experience due to environmental temperature changes?

Drift error Signup and view all the answers

What is the Mach number condition for considering flow as incompressible?

M ≤ 0.3 Signup and view all the answers

In thermal anemometry, what is the role of thermal conductance in measuring fluid velocity?

It increases with fluid velocity. Signup and view all the answers

For supersonic flow (M > 1), what must be used to calculate local velocity?

Rayleigh relation Signup and view all the answers

Which type of sensor in thermal anemometry operates with a thin film of platinum or gold?

Hot-film Signup and view all the answers

What is the relationship between heat transfer (Q) and cooling velocity in thermal anemometry?

Q = A + B * U^n Signup and view all the answers

Study Notes

Inclined Tube Manometer

Measures small pressure changes using a U-tube design with one leg inclined at an angle (typically 10 to 30 degrees).
Useful for low-density fluid pressure measurements.

Shear Forces and Viscosity

Shear forces act parallel to a surface, impacting fluid behavior.
Resistance to shear in fluids is linked to viscosity; high viscosity indicates greater resistance.

Buoyancy

An object's buoyancy in a fluid equals the weight of the fluid displaced, explaining why some lighter objects float while denser ones may sink yet are easier to move underwater.

Pressure Transducers

Categories include:
- Absolute: Measures against absolute zero pressure.
- Gauge: Measures pressure relative to atmospheric pressure.
- Vacuum: A variation of absolute, used for low-pressure measurements.
- Differential: Measures the difference between two pressures.
Common errors include resolution, zero shift error, linearity, sensitivity, hysteresis, noise, and temperature-induced drift.

Mach Number

Defined as M = U / a, where U is local velocity and a is the speed of sound.
Flow is considered incompressible when M ≤ 0.3; significant errors arise when M > 0.3.

Thermal Anemometry

Measures fluid velocity based on heat transfer principles.
Sensor typically uses a metallic RTD element and operates on current-based heating.
Two operating modes: Constant Current (CC) and Constant Resistance (CR).
High sensitivity at low velocities with frequency limits determined by Strouhal frequency.

Doppler Anemometry

Relies on the Doppler Effect where wave frequency shifts due to the motion between source and observer.
Measures local fluid velocity using particles causing Doppler shifts in emitted laser light.
Dual-Beam Mode increases measurement accuracy by separating Doppler frequencies.

Mass Flow Rate

Calculated as mass flux times area (A = π.r²).
Units measured in kg/s or lbm/s.
Accurate mass flow measurement requires sensitivity to fluid density and velocity.

Volume Flow Rate

Depends on average velocity over the flow's cross-section.
Units measured in m³/s or ft³/s.
Distinguished from mass flow rate, which requires density consideration.

Flow Characteristics

Flow can be classified as laminar, turbulent, or transitional based on the Reynolds number (Re).
- Laminar: Re < 2000
- Transitional: 2000 ≤ Re ≤ 4000
- Turbulent: Re > 4000
Hydraulic diameter used for non-circular conduits.

Flow Measurement Installation

Sufficient straight lengths before and after flow meters are crucial for accurate measurements to minimize disturbances.
Downstream pressure recovery is necessary for stable flow post-meter passage.
Elbows and bends should be carefully considered during placement to avoid inaccuracies in flow measurements.

Description

Test your understanding of key fluid mechanics concepts including inclined tube manometers, shear forces, viscosity, buoyancy, and pressure transducers. This quiz covers essential principles and measurement techniques in fluid dynamics.