Sediment Size Effects in Acoustic Doppler Velocimeter-Derived Estimates of Suspended Sediment Concentration

Abstract

Backscatter output from a 10 MHz acoustic Doppler velocimeter (ADV) was used to quantify suspended sediment concentrations in a laboratory setting using sand-sized particles. The experiments included (a) well-sorted sand samples ranging in size from 0.112 to 0.420 mm, obtained by the sieving of construction sand, (b) different, known mixtures of these well-sorted fractions, and (c) sieved natural beach sand with median sizes ranging from 0.112 to 0.325 mm. The tested concentrations ranged from 25 to 3000 mg·L −1 . The backscatter output was empirically related to concentration and sediment size, and when non-dimensionalized by acoustic wavelength, a dimensionless sediment size gradation coefficient. Size-dependent upper and lower bounds on measurable concentrations were also established empirically. The range of measurable conditions is broad enough to make the approach useful for sand sizes and concentrations commonly encountered in nature. A new method is proposed to determine concentrations in cases of mixed-size sediment suspensions when only calibration data for well-sorted constituent sands are available. This approach could potentially allow better estimates when the suspended load is derived from but is not fully representative of the bed material, and when the size characteristics of the suspended material are varying in time over the period of interest. Differences in results between the construction and beach sands suggest that sediment shape may also need to be considered, and point to the importance of calibrating to sediments encountered at the site of interest.

Characterizing the Composition of Sand and Mud Suspensions in Coastal and Estuarine Environments Using Combined Optical and Acoustic Measurements

“…The OBS was initially calibrated using sandy sediment obtained from the seabed adjacent to the measurement frame, as is frequently done in practice (Fettweis et al, 2019;Paphitis & Collins, 2005). However, there is still concern that calibration using bed material can be inappropriate and error-prone if there are significant differences between the bed sediment and material in suspension (Bass et al, 2007;Beamsley et al, 2001;Kineke & Sternberg, 1992;Öztürk, 2017;Su et al, 2016), as expected at our field site. On this basis, the original calibration was discarded when it was recognized that the additional presence of suspended sediment significantly finer than the bed sediment made interpretation ambiguous.…”

“…Only the latter is specifically designed to measure suspended sediment concentration; ADCPs and ADVs were originally intended to measure velocity, but their operating principles mean that inferring sediment concentration from acoustic backscatter is a useful side benefit. In this study, we mainly consider acoustic backscatter from ADVs, which are widely used to measure suspended sediment concentrations (Fugate & Friedrichs, 2002; Lin et al., 2020; Öztürk, 2017).…”

In-situ long-period monitoring of suspended particulate matter dynamics in deep sea with digital video images

“…In the last decade much work has been done to measure SPM concentration by optical/acoustic backscatter (Fugate and Friedrichs, 2002;Downing, 2006;Sahin et al, 2019). Commonly, the relationship between optical backscatter signal and SPM concentration was almost linear (Haalboom et al, 2021), and the acoustic backscatter signal was logarithmically proportional to the SPM concentration (Rouhnia et al, 2014;Öztürk, 2017;Sahin et al, 2017). In this section, we compared the image signal with the optical/ acoustic backscattering signal.…”

Türbülans parametrelerinin ölçümü ve türbülans kinetik enerjisinin oksijen transferine etkisi

“…ADV sinyal dönüş verisi sediment konsantrasyonu ve tanecik büyüklüğü ile deneysel olarak ilişkilidir, bu değerler akustik dalga boyu değerleriyle boyutsuzlaştırıldığında sediment büyüklükleri ile bağıntılı geçiş katsayıları elde edilmektedir. [11].…”