Acoustic measuring techniques for suspended sediment

28th IAHR symposium on Hydraulic Machinery and Systems

Gruber, P.^1 ; Felix, D.^2 ; Storti, G.^3 ; Lattuada, M.^4 ; Fleckenstein, P.^3 ; Deschwanden, F.^1

Competence Center for Fluid Mechanics and Hydro Machines (CC FMHM), Hochschule Luzern (HSLU), Technikumstrasse 21, Horw

CH-6048, Switzerland^1

Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zürich, Hönggerberg-ring 26, Zurich

CH-8093, Switzerland^2

Institute for Chemical and Bioengineering, ETH Zürich, Vladimir Prelog Weg 1-5/10, Zurich

CH-8093, Switzerland^3

Adolphe Merkle Institute-Nanoparticles Self-Assembly, Université de Fribourg, Chemin des Verdiers 4, Fribourg

CH-1700, Switzerland^4

关键词: Backscattered signal;    Discharge measurements;    Frequency dependencies;    Low signal-to-noise ratio;    Measuring technique;    Sediment monitoring;    Simultaneous determinations;    Suspended sediment concentrations;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/49/12/122003/pdf
DOI  :  10.1088/1755-1315/49/12/122003

来源: IOP

【 摘 要 】

Acoustic signals can be used in various ways for suspended sediment monitoring. One possibility which lends itself particularly well in the context of hydropower plants (HPPs), is to use installations for acoustic discharge measurement (ADM). Such installations already exist at waterways of many HPPs. Similar to certain turbidimeters, the attenuation of the forward scattered signal travelling through the water-sediment mixture is correlated with suspended sediment concentration (SSC). This correlation can be based on reference SSCs, e.g. from gravimetric analyses of bottle samples. Without the need of additional sensors and practically maintenance-free, this method is used successfully in the HPP Fieschertal to warn the HPP operator of high SSC to prevent excessive turbine abrasion. Acoustic methods and systems that allow for estimating both SSC and particle size distribution (PSD) are under development. The simultaneous determination of SSC and PSD is not possible using a single frequency. Therefore, multi-frequency approaches are investigated for generally scattered signals. When backscattered signals are used, a stronger frequency dependency can be exploited. However, the reliable simultaneous determination of particle size (and distribution) and concentration is still a major challenge due to a low signal-to-noise ratio and an ill- posed problem of estimating concentration and size from recorded signals. The optimal setup configuration (angles, frequencies) for such a system is not unique and further investigations are recommended.