Question

A three-dimentional flow velocity can be measured by using various method. Please name
two devices that use a probe and two sophisticated devices without a probe usage for the
three-dimentional flow velocity measurement.

Answer 1

1) The devices that uses a probe for the velocity measurement are: a) Pitot tube, b) Hot wire anemometer

a) Pitot tube: A pitot tube is just a tube with pressure tap at the stagnation point that measures stagnation pressure. The pitot static probe measures local velocity by measuring the pressure difference in conjunction with the Bernoulli's equation.

Above is known pitot formula.

b) Hot wire anemometer: They involve an electrically heated sensor and utilize a thermal effect to measure flow velocity. Anemometers have extremely small sensors and thus they can be used to measure the instantaneous velocity at any point in the flow without appreciably disturbing the flow.

2) The devices without a probe for the velocity measurement are: a) Venturi Meter, b) Electromagnetic flowmeter

a) Venturi Meter: Venturi meter is a converging diverging passage through which fluid passes and with the help of Bernoulli's and continuity equation we can find the velocity.

b) Electro Magnetic Flowmeter: A full flow electromagnetic flow meter in a non-intrusive device that consists of a magnetic oil that encircles the pipe and two electrodes drilled into the pipe along a diameter. The potential difference created is proportional to the flow velocity of the fluid and thus the flow velocity can be calculated by relating it to voltage generated.