3D-LDA System

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The 3D fiber-optics LDA system of the LTT/NTUA comprises a 2D optical probe, powered by a 5-watt argon-ion laser, that makes use of the green and blue beams to measure two orthogonal velocity components, and a 1D probe, powered by an infrared laser-diode, that measures the third non-orthogonal velocity component. This third velocity component is measured in the plane of the green beam pair. The system is intended for measurements in turbomachinery components with limited optical access. The angle between the two probes is thus limited to between 20 and 40 degrees, depending on the allowed separation between the two probes and the focal length requirements for the lenses. The system has been successfully employed for the measurement of mean velocity distributions in complex high-speed 3D turbomachinery flows, while some data on the RMS fluctuations of individual components have also been acquired.