Design of an Optical Box for Laser Doppler Anemometer Measurements

This report is about Design of an optical box for Laser Doppler Anemometer
measurements and fluid velocity measurement using Laser Doppler Anemometer.
Laser Doppler Anemometer uses a beam of light from laser to measure velocity of fluid
flows. The objective of the project is to design a module of laser Doppler anemometer
that can simplifY mathematical derivation for refraction correction of velocity
measurement and to run a test on the test section to obtain transversal measurement of
fluid velocity very close to the pipe wall. The main factor to be considered in the
experiment is the refractive index of the elements used. The design will include acrylic
pipe tube with '+' cross slit on the pipe wall, Teflon film to cover the cross slit, a gear,
and a connecting device to connect the test section to the pipe section. The pipe needs to
be rotatable so .that it can be used to measure the velocity of fluid flow at different
points. The experiments will be conducted using LDA laser which will pass through
different types of medium before reaching the fluid interface. Mathematical derivation
can be simplified by having the optical box and a cross slit on the pipe wall, which will
reduce refraction as the beams goes through the box, fluid inside the box and straight to
the fluid inside the pipe by eliminating the effect of pipe curvature. For that, refraction
needs to be as small as possible in such way that angle of incident is almost the same
with angle of refraction (zero refraction), where the refractive index of the pipe wall and
the Teflon film covering the slit are similar to the fluid being tested.