Measurements in ducted flows by laser-Doppler anemometry

The merits of small-scale, water-flow experiments with measurements by laser-Doppler anemometry are indicated in relation to previously reported results. New measurements are reported in a square-to-round transition duct and show that, for example, the pressure forces overwhelm any small normal-stress driven secondary flows in the inlet plane to given maximum values of around 0.07 of the bulk velocity in the exit plane. The precision of manufacture of the ducts means that the geometric boundary conditions are accurately known and the results are therefore suitable for calculation purposes. Similarly, the instrumentation allows the flow boundary conditions to be accurately determined.