Laser Doppler Velocimetry
This technique uses small tracer particles added to the flow (oil, particles with diameter below 1 micrometer).
These particles scatter light projected by two laser beams into a small measurement volume. In this volume these
laser-beams interfere producing interference planes (tiny planes of light one behind the other). The particle
reflects the light when flying through these planes ; The frequency of these light flashes allows the calculation
of the velocity if the distance between the interference planes is known.
MPEG video (506 KB)
For our work we use a commercially available LDV system together with four other institutes at the Faculty of
Mechanical Engineering. This system consists of a Coherent Innova 90/6 , a two-dimensional DANTEC Fiberflow
probe system, two DANTEC Burst Spectrum Analyser for real time Fourier processing of the signal and a DANTEC
590x590x690mm computer-controlled traverse. Additionally this system can be used with a DANTEC PDA Processor
for particle sizing. A small DANTEC Flow Lite system is supporting the students lab and outdoor measurements.
(for details on the systems visit DANTEC homepage)
GIF picture (86KB)
Together with flow visualisation and interferometric techniques LDV measurements are used for precise velocity
measurements in transonic flow in a linear cascade as well as in rotating machinery. The picture shows the
result of a LDV measurement in the linear turbomachinery blade
cascade of the institute. Currently experiments using LDV technique are performed for the study
of turbine blade wake turbulence (Project S6801)
and turbine blade cooling flow aerodynamics