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In situ characterization of suspended sediment by acoustic techniques

Objective



There is a great need for reliable measurements of sediment
properties and transport for field studies, in particular
along coasts and in estuaries. Especially, it is now
increasingly recognized that better field data are required to ensure the proper validation and calibration of rather
sophisticated sediment transport models. However, suitable
instrumentation is not available at present. The general
objective of the project is to make the first step to fill
this gap using wide band acoustic methods (frequency range
from 100 kHz to 100 MHz). The advantage over more traditional techniques is that a single instrument can provide estimates of profiles in the water column or near the seabed.
The measured parameters are the sediment concentration (range: about 0.01 - 10 kg/m3), the particle size distribution (range: about 5-500 um), and, in combination with standard Doppler
techniques, the sediment transport.

The first goal of the project is to provide a knowledge base on the subject. At present there is a lack of physical
knowledge regarding the interaction process between the
acoustic waves and the sediment particles. To obtain this,
carefully tuned experimental and theoretical research will be carried out.
The second main objective is to detail this knowledge further, both theoretically and experimentally, in order to make it
directly useful for the development of instrumentation for
suspended sediment characterization. For example, the general fundamental theoretical model description will be extended, in order to describe real experimental conditions (e.g., geometry and patterns of the acoustic beams). This will allow a
detailed comparison with experimental results and is needed
for the design of research-phase instrumentation. In parallel (third objective), a research-phase acoustical instrument will be developed, tested and compared with optical instrumentation (under development outside the scope of the present project). A combination of acoustic and optical methods, which could
extend the size range down to about 0.1 um at low
concentrations (below 1 kg/m3), will be evaluated.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

STICHTING WATERLOOPKUNDIG LABORATORIUM (WL/DELFT HYDRAULICS)
Address
185,Rotterdamseweg 185
2600 MH Delft
Netherlands

Participants (2)

Danmarks Tekniske Universitet
Denmark
Address
100,Lundtoftevej
2800 Lyngby
IFREMER - INSTITUT FRANÇAIS DE RECHERCHE POUR L'EXPLOITATION DE LA MER
France
Address
Technopôle De Brest - Iroise
29280 Plouzane