Laser transit velocimetry

Abstract

The article starts with a short overview about the history of the development of Laser Transit Velocimetry (LTV) also known as Laser Two Focus Velocimetry (L2F). The advantageous properties of LTV are explained which qualify this technique for high speed and turbomachinery flows and for near wall measurement applications. The fundamentals are then treated describing the general principal, the statistical data evaluation and the prospects of measuring turbulence statistics. Next, a state of the art LTV system is considered presenting details about the optical set up, the measurement procedure and the data processing and evaluation methods. In the second part of the article 3-component LTV techniques are treated with the main emphasis placed on the recently developed 3-component-Doppler-L2F velocimeter. In this hybrid system the L2F-principle is combined with a Doppler-frequency shift analysis by which the velocity component in the direction of the optical axis is determined. The unique measurement system is described in detail and examples of applications are presented.