ADV measurements of turbulence: Can we improve their interpretation?

A simple technique to reduce the Doppler noise influence on measurements of turbulence using the Acoustic Doppler Velocimeter (ADV) is developed, and basic relationships to estimate turbulence characteristics using information about the Doppler noise are derived. The procedure involves, firstly, measurement of instantaneous velocities in the flow under consideration; secondly, measurement of the Doppler noise components in still water taken from the Bow investigated (with the same velocity range setting that was used in turbulence measurements); and thirdly, estimation of turbulence characteristics using both sets of measurements and relationships developed in the paper. The technique was tested for three typical environments (water storage basin with silty water, laboratory flume with water containing seeding material of neutrally buoyant hollow glass spheres with a mean size around 8-10 mu m, and outdoor flume with natural water containing air bubbles and organic particles). It was shown that the Doppler noise can change the measured turbulence characteristics significantly, even for high-level turbulence flows.