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convenient velocity data. Many varieties of commercial hot-wire equipment are available, as are do-it-yourself designs . Excellent detailed discussions of the hot wire
are given in Refs. 1 and 28.
Because of its frailty, the hot wire is not suited to liquid flows, whose high density
and entrained sediment will knock the wire right off. A more stable yet quite sensitive
alternative for liquid-flow measurement is the hot-film anemometer (Fig. 6.29f). A thin
metallic film, usually platinum, is plated onto a relatively thick support which can be
a wedge, a cone, or a cylinder. The operation is similar to the hot wire. The cone gives
best response but is liable to error when the flow is yawed to its axis.
Hot wires can easily be arranged in groups to measure two- and three-dimensional
velocity components. | v v Laser-doppler anemometer. In the LDA a laser beam provides highly focused, coherent monochromatic light which is passed through the flow. When this light is scattered
from a moving particle in the flow, a stationary observer can detect a change, or doppler...
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- Spring '08