Communication Dans Un Congrès Année : 2008

Suspended solids and attenuation of ultrasonic beam

Résumé

Acoustic flow-meters are gauging devices commonly used in urban hydrology. Many of them are based on the Doppler principle and their use is based on the hypothesis that the velocity of suspended particles is equal to the flow velocity. Thus, at least a small amount of backscattering particles (or bubbles) is required for the use of acoustic Doppler velocimeters. In the same time, due to thermal conductivity and viscosity effects, the intensity of an ultrasonic wave propagating in an homogeneous medium decreases. In suspension an additional attenuation due to scattering and absorption by particles contribute to the intensity decay. This term depends on the particles nature and concentration. There is a complete lack of data for runoff and wastewaters. Moreover the density of the particles ranges between 1.03 and 1.3 and their granulometry is roughly known. In order to quantify the attenuation by wastewaters solids, an experimental set-up has been developed. The attenuation measurement for various types of particles is presented. It appears that the attenuation of the ultrasonic beams by the particles in suspension within the wastewaters, at the common wastewaters concentration, is negligible and that most of the observed attenuation is due to deposit on the gauges within the water column.

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Dates et versions

hal-00614118 , version 1 (09-08-2011)

Identifiants

  • HAL Id : hal-00614118 , version 1

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Frédérique Larrarte, Pierre François. Suspended solids and attenuation of ultrasonic beam. 11th International Conference on Urban Drainage, Aug 2008, France. ⟨hal-00614118⟩
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