ch5: Flashcards
(49 cards)
What does flow measurement euberian?
It measures velocity and direction at a fixed point.
What are the types of eulerian methods?
Mechanical, acoustic, electromagnetic, radar.
What does a Lagrangian method follow?
The movement of a water parcel.
What is an example of a Lagrangian instrument?
GPS floats.
How does a propeller measure flow?
By counting revolutions per time = flow velocity.
What does propeller reading depend on?
Flow conditions.
What is used to compare direction?
A compass added to the flow meter.
Why are multiple measurements needed?
To get full profile of flow.
What does acoustic travel time measure?
Flow by analyzing travel time of signal.
What affects travel time?
Distance, flow velocity, sound velocity.
What affects sound velocity?
Temperature and conductivity.
What principle does ADCP use?
Doppler shift of particles.
What does ADCP calculate?
Velocity based on travel time and frequency.
What does ADCP provide?
Vertical velocity profiles and 3D flow components.
Where is ADCP installed?
On boats or fixed platforms.
What does bottom tracking measure?
Speed and position.
What is the blanking zone?
Area near transducer affected by noise.
What principle does EMV use?
Faraday’s law.
What does EMV measure?
Voltage from fluid in magnetic field → flow velocity.
Where is EMV used?
Low-flow environments, small channels.
What does HF Radar measure?
Surface currents using EM waves (3–50 MHz).
What does a buoy scatterometer measure?
Wave profile using backscatter.
What principle do drifter buoys use?
Lagrangian technique (floating device).
What is the GPS accuracy in drifter buoys?
1–3 m.
