A simple method for calculating in situ floc settling velocities based on effective density functions

Markussen, Thor Nygaard; Andersen, Thorbjørn Joest

doi:10.1016/j.margeo.2013.07.002

Cited by 36 publications

(24 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The settling velocity can then be derived if the relationship between effective density and floc size is established. This has been done, e.g., by assuming a self‐similarity between primary particles and flocs based on fractal theory [ Kranenburg , ; Winterwerp , ] or by using density functions that describe the mass distribution over the PSD [ Markussen and Andersen , ]. The settling velocity was calculated for each of the four aggregate groups of primary particles, flocculi, microflocs, and macroflocs separately, using the modified Stokes' equation [ Lee et al ., ]:

w_{s, i} = \frac{ρ_{p} - ρ_{w}}{18 μ} g D_{p}^{3 - n f_{i}} \frac{D_{i}^{n f_{i} - 1}}{1 + 0.15 R e_{i}^{0.687}}

where w s , i is the settling velocity of the i th aggregate group.…”

Section: Methodsmentioning

confidence: 99%

Seasonal variation in concentration, size, and settling velocity of muddy marine flocs in the benthic boundary layer

Fettweis

Baeye

2015

JGR Oceans

View full text Add to dashboard Cite

Suspended Particulate Matter (SPM) concentration profiles of the lowest 2 m of the water column and particle size distribution at 2 m above the bed were measured in a coastal turbidity maximum area (southern North Sea) during more than 700 days between 2006 and 2013. The long-term data series of SPM concentration, floc size, and settling velocity have been ensemble averaged according to tidal range, alongshore residual flow direction, and season, in order to investigate the seasonal SPM dynamics and its relation with physical and biological processes. The data show that the SPM is more concentrated in the near-bed layer in summer, whereas in winter, the SPM is better mixed throughout the water column. The decrease of the SPM concentration in the water column during summer is compensated by a higher nearbed concentration indicating that a significant part of the SPM remains in the area during summer rather than being advected out of it. The opposite seasonality between near-bed layer and water column has to our knowledge not yet been presented in literature. Physical effects such as wave heights, wind climate, or storms have a weak correlation with the observed seasonality. The argument to favor microbial activity as main driver of the seasonality lies in the observed variations in floc size and settling velocity. On average, the flocs are larger and thus settling velocities higher in summer than winter.

show abstract

w_{s, i} = \frac{ρ_{p} - ρ_{w}}{18 μ} g D_{p}^{3 - n f_{i}} \frac{D_{i}^{n f_{i} - 1}}{1 + 0.15 R e_{i}^{0.687}}

where w s , i is the settling velocity of the i th aggregate group.…”

Section: Methodsmentioning

confidence: 99%

Seasonal variation in concentration, size, and settling velocity of muddy marine flocs in the benthic boundary layer

Fettweis

Baeye

2015

JGR Oceans

View full text Add to dashboard Cite

show abstract

“…FV directly determines the vertical distribution of suspended sediment concentration (SSC) and near-bed deposition flux, and its accurate determination has been regarded as a priority in characterizing fine sediment transport. In the past, extensive efforts, e.g., (Fennessy et al, 1994;Gratiot et al, 2005;Krishnappan et al, 2004;Markussen and Andersen, 2013;McLaughlin, 1961;Mehta, 1989;Owen, 1971;Rouse, 1938;van Leussen, 2011), have been made to enhance our understanding of the physical process of fine sediment settling and a number of empirical and semi-empirical formulas for FV have been proposed in various forms.…”

Section: Introductionmentioning

confidence: 99%

“…Another insurmountable problem preventing in situ FV measurement is that this method cannot distinguish individual flocs under high SSC condition. Even slight increases in SSC can cause single flocs to become entirely indistinguishable, meaning that the method is only valid for relatively low SSC (Markussen and Andersen, 2013). (3) The use of laboratory experiment (by settling column) for measuring the FV has a long history (Camp, 1936;Fathi-Moghadam et al, 2011;McLaughlin, 1961;van Leussen, 1988).…”

Section: Introductionmentioning

confidence: 99%

Experimental study on fall velocity of fine sediment in the Yangtze Estuary, China

Wan

Roelvink

et al. 2015

Ocean Engineering

View full text Add to dashboard Cite

“…Laser in situ scattering and transmissometry (LISST) has been widely used to measure PSD in marine sediments, phytoplankton community and other natural particle assemblages, providing high-frequency and continuous PSD results (Czuba et al, 2015;Fettweis et al, 2014;Markussen and Andersen, 2013;Renosh et al, 2014;Reynolds et al, 2010;Xi et al, 2015). LISST greatly improves our understanding of PSD in seawater, but the SPM composition remains unclear.…”

Section: Introductionmentioning

confidence: 99%

Particle size distributions and organic-inorganic compositions of suspended particulate matters around the Bohai Strait

Wang

Bian

et al. 2017

J. Ocean Univ. China

View full text Add to dashboard Cite

Laser in situ scattering and transmissometry (LISST) significantly improves our ability to assess particle size distribution (PSD) in seawater, while wide-ranging measurements of the organic-inorganic compositions of suspended particulate matters (SPM) are still difficult by using traditional methods such as microscopy. In this study, PSD properties and SPM compositions around the Bohai Strait (China) were investigated based on the measurements by LISST in combination with hydro-biological parameters collected from a field survey in summer 2014. Four typical PSD shapes were found in the region, namely right-peak, left-peak, double-peak and negative-skew shapes. The double-peak and negative-skew shapes may interconvert into each other along with strong hydrodynamic variation. In the upper layer of the Bohai Sea, organic particles were in the majority, with inorganic particles rarely observed. In the bottom layer, SPM were the mixture of organic and inorganic matters. LISST provided valuable baseline information on size-resolved organic-inorganic compositions of SPM: the size of organic particles mainly ranged from 4 to 20 µm and 40 to 100 µm, while most SPM ranging from 20 to 40 µm were composed of inorganic sediment.

show abstract

A simple method for calculating in situ floc settling velocities based on effective density functions

Cited by 36 publications

References 37 publications

Seasonal variation in concentration, size, and settling velocity of muddy marine flocs in the benthic boundary layer

Seasonal variation in concentration, size, and settling velocity of muddy marine flocs in the benthic boundary layer

Experimental study on fall velocity of fine sediment in the Yangtze Estuary, China

Particle size distributions and organic-inorganic compositions of suspended particulate matters around the Bohai Strait

Contact Info

Product

Resources

About