Dual-Measurement-Method and its extension for accurately resolving the secondary flows in LDA (Laser Doppler Anemometry) applications

In order to accurately resolve the secondary flow structures across the main flow, a method known as the Dual-Measurement-Method (DMM) has been developed and shown to be very efficient. The method is based on the “reflection design” of the LDA layout and aims to find out the velocity shift existing in the measurement results. For situations where the “reflection design” of the LDA layout is restricted, the Dual-Measurement-Method has been extended in a way that three arbitrary measurements have to be carried out. The calculation processes in finding out the velocity shift from three such measurements have been outlined and validated. An example of use indicates that just in that case the secondary flows have to be resolved as accurately as possible.