A Study of Some Measurement Errors in L2F - Velocimetry

In high speed flows the measurement accuracy of Laser-Two-Focus velocimetry is mainly determined by the statistical error due to insufficient number of sampled particles. Nevertheless there exist a lot of other sources of measurement error which may reduce the accuracy of the results: The geometry of the measurement volume leadsto systematic errors in the turbulence degree. Windows which permit optical access to the internal flow may disturb the flow or distort the Laser measurement volume. The evaluation procedure may add some uncertainty. In the present study some of these measurement errors have been investigated numerically. In some cases systematic errors can be circumvented or may be corrected quantiatatively. It can also be shown that measurement time may be reduced by choosing adequate parameters for the L2F-device and the measurement procedure, without affecting measurement accuracy.