Sediment concentration measurement by transverse suction

Bosman, J.J.; Velden, Elsbeth T.J.M. van der; Hulsbergen, C.H.

doi:10.1016/0378-3839(87)90033-0

Cited by 69 publications

(46 citation statements)

References 2 publications

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“…This arrangement yields a trapping ratio (measured concentration divided by true concentration) less than unity because the sediment particles cannot always follow the curved fluid paths into the intake tubes. The concentrations were corrected for this effect (Bosman et al 1987). The intake velocity was about 1.4 re~s, satisfying sampling requirements.…”

Section: Methodsmentioning

confidence: 90%

Transport of Fine Sands by Currents and Waves

Rijn¹,

Nieuwjaar

Kaay

et al. 1993

J. Waterway, Port, Coastal, Ocean Eng.

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ABSTRACT:The transport process of fine sands in combined current and wave conditions in a flume was studied. Two types of sediment material were used, a very fine sand with a median diameter of about 100 ~m and a medium-fine sand with a diameter of 200 txm. The current velocities were varied in the range of 0.1-0.5 m/s (following and opposing the waves). Irregular waves with a single-topped spectrum and peak period of 2.5 s were generated. The significant wave height varied in the range of 0.075 m to 0.18 m. The water depth was about 0.5 m in all tests. Time-averaged fluid velocities were measured by an electromagnetic current meter. Time-averaged sediment concentrations were measured by a pump sampler. The transport rate was obtained by integration of the product of velocity and concentration over the depth. The generation of waves in following or opposing currents causes a decrease of the time-averaged velocities in the near-bed region. A larger wave height results in larger concentrations and in a more uniform distribution over the depth. The influence of the current direction on the concentration profile and the transport rate is negligible.

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Section: Methodsmentioning

confidence: 90%

Transport of Fine Sands by Currents and Waves

Rijn¹,

Nieuwjaar

Kaay

et al. 1993

J. Waterway, Port, Coastal, Ocean Eng.

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“…Waves were generated for sufficient time to allow bed ripples to develop and stabilize. Time-averaged concentrations of suspended quartz and heavy minerals entrained from the rippled bed were measured using a transverse suction (TS) system (Bosman et al 1987). Rather than one multi-intake tube array positioned over a selected bed feature (e.g., McFetridge and Nielsen 1985), six separate intakes spanning the middle third of the test section were used.…”

Section: Methodsmentioning

confidence: 99%

“…These values indicate that the intakes are not preferential in terms of sampling particular grain sizes. It is expected that the intakes would probably catch at least 75% of all suspended particles (Bosman et al 1987). Following collection of suspended sediment the flume was fully drained to enable profiling of ripple features and bed levels photographically and with a rail-mounted pointer gauge.…”

Section: Methodsmentioning

confidence: 99%

Selective Entrainment of Sediment Graded by Size and Density Under Waves

Tomkins¹,

Nielsen²,

Hughes³

2003

Journal of Sedimentary Research

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The influence of near-bed sorting processes on heavy mineral content in suspension is discussed. Sediment concentrations above a rippled bed of mixed quartz and heavy mineral sand were measured under regular nonbreaking waves in the laboratory. Using the traditional gradient diffusion process, settling velocity would be expected to strongly affect sediment distribution. This was not observed during present trials. In fact, the vertical gradients of time-averaged suspension concentrations were found to be similar for the light and heavy minerals, despite their different settling velocities. This behavior implies a convective rather than diffusive distribution mechanism. Between the nonmoving bed and the lowest suspension sampling point, light and heavy mineral concentration differs by two orders of magnitude. This discrimination against the heavy minerals in the pickup process is due largely to selective entrainment at the ripple face. Bedform dynamics and the nature of quartz suspension profiles are found to be little affected by the trialed proportion of overall heavy minerals in the bed (3.8-22.1%).

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“…Much of the analysis that follows rests on measurements of sediment concentration made by pumped sampling; here the procedures of Bosman et al (1987) guided the sampling methodology.…”

Section: Experiments In a Full-scale Wave Flumementioning

confidence: 99%

On the suspension of graded sediment by waves above ripples: Inferences of convective and diffusive processes

Davies

Thorne

2016

Continental Shelf Research

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The relationship between the grain size distribution of the sediment on the bed and that found in suspension due to wave action above ripples is assessed here using detailed, pumped sample, measurements obtained at full-scale and also at laboratory scale. The waves were regular and weakly asymmetrical in most tests, and irregular in a minority of tests. The beds comprised fine and medium sand and were rippled in all tests. The cycle-mean sediment concentrations (C) from the pumped samples were split into multiple grain size fractions and then represented by exponential Cprofile shapes. The analysis of these profiles was carried out in two stages to determine: i) the relationship between the size distribution of the sediment on the bed and that found in the reference concentration, and ii) the behaviour of the exponential decay scale of the C-profiles. From this analysis inferences are made about the relative roles of diffusion and convection in the upward sediment flux linked to the process of vortex shedding from the ripple crests. The Transfer Function (Tr) defined to relate the bed sediment size distribution to that of the reference concentration indicates that, while finer fractions are relatively easily entrained, the suspension of some coarser fractions is caused by an additional convective effect that supplements diffusion. The evidence for this becomes pronounced above steep ripples, and the Transfer function suggests further that irregular waves increase the occurrence of coarser fractions in suspension. A functional form for Tr is suggested incorporating these principles. The exponential decay scale LS arising from the fractional C-profiles is also examined to assess the mechanisms responsible for the upward transfer of grains and a parameterisation of LS related to ripple size is suggested. The separate findings for Tr and LS present supporting evidence of diffusion affecting the finer fractions in suspension and combined diffusion + convection affecting the coarser fractions. The methodology developed allows the vertical profile of suspended median grain size to be predicted given knowledge of both the bed grain size distribution and also the flow conditions.

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Sediment concentration measurement by transverse suction

Cited by 69 publications

References 2 publications

Transport of Fine Sands by Currents and Waves

Transport of Fine Sands by Currents and Waves

Selective Entrainment of Sediment Graded by Size and Density Under Waves

On the suspension of graded sediment by waves above ripples: Inferences of convective and diffusive processes

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