UKSBS RE18258 3 Nortek Vector ADVs

Three acoustic Doppler velocimeters (ADV) for single point velocity measurements are required for field observations of currents, turbulence, and sediment fluxes. The instrument functions by sending an acoustic ping, which is scattered by natural particles in the water and received by three transducers. ADVs are the state-of-the-art instruments for single point measurements. Important features of the ADV are the single-point measurement of the three components velocity (u,v,w) from which the three turbulent fluctuating components (u',v',w') can be extracted, and the fast sampling rates. These fast sampling rates (faster than 8 Hz and often up to 32 Hz) are required to resolve the entire turbulence spectra, and slower rates severely limit the scientific validity of the data. The backscatter signal can also be used for sediment fluxes. The instrument must also be designed for use in harsh nearshore (beaches, surf zones) and estuarine environments. A laboratory version of the ADV exists, but for the work of the National Oceanography Centre these are not appropriate as we require robust instruments that are able to be deployed without a computer or external power supply.