Modelling of sediment suspensions in oscillating grid turbulence

Abstract

A k -model is used to describe the steady state of ÿne-grained sediments maintained in suspension by purely di usive turbulence, as generated in oscillating grid turbulence experiments. The behaviour is shown to depend both on the bulk Rouse number Rou 0 and the product of the bulk Rouse number and the bulk Richardson number Ri 0 Rou 0 , built on oscillating grid parameters. For Rou 0 ¡ 0:01, concentrated suspensions are observed with a homogeneous particle concentration in the suspension layer. An interface, called lutocline, separates the suspension layer from the clear water at a distance z m from the grid. The depth of the suspension layer is found to vary as z m =z 0˙( Ri 0 Rou 0 ) −1=4 . For Ri 0 Rou 0 1 the decay of turbulence is a ected by the particle concentration only in a region very close to the interface. In this case the ux Richardson number approaches the value of 1 near the interface. The lutocline is seen to vanish for large values of Rou 0 . For Rou 0 ¿ 0:01 the mean sediment concentration and turbulence decay simultaneously with increasing distance from the grid, and no sharp interface is observed.

A model of the vertical distribution of suspended sediment in the bottom layer of a natural water body

“…(27), we just refer to the qualitative resemblance of the distributions depicted in Fig. 2 with the similar observed and/or modelled distributions published in Kirby & Parker (1983), E & Hopfinger (1989), Noh & Fernando (1991) and Michallett & Mory (2004).…”

“…The major disadvantage of these approaches has been insufficient physical justification of the adopted dependences, revealed mostly in attempts to explain the concentration distributions with the presence of the lutocline. The lutocline was first observed in data measured in the Severn Estuary and Inner Bristol Channel (Kirby & Parker 1983) and was thereafter studied in several experimental (Kirby 1986(Kirby , 1992Mehta 1988;E & Hopfinger 1989;Wolanski et al 1989;Mehta & Srinivas 1993) and model investigations performed on semi-empirical background (Smith & Kirby 1989;Gross & Nowell 1990;Noh & Fernando 1991;Toorman & Berlamont 1993;Michallett & Mory 2004;Yoon & Kang 2005).…”

“…The derived formula is tested against laboratory data reported in Coleman (1986), where the lutocline was not observed. Data on detailed model testing for the case with the presence of the lutocline are not available, therefore in this case the comparison is limited to showing the qualitative similarity between the model-predicted effects and the respective effects observed and/or modelled in other studies (Kirby & Parker 1983;E & Hopfinger 1989;Noh & Fernando 1991;Michallett & Mory 2004).…”

Oscillating-grid turbulence and its applications: a review/ Turbulence de grille oscillante et ses applications: une revue

“…Such an example was given by Matsunaga et al (1999), who reported that the turbulent kinetic energy and dissipation rate of OGT could be computed from the k-ε turbulence model, and their analysis appeared in good agreement with experimental data. Michallet and Mory (2004) also extended the k-ε model to the study of sediment suspension induced by OGT. However, uncertainties could be involved in using k-ε model which is developed largely based on the characteristics of shear-affected flow for this purpose.…”

A model of vertical distribution of suspended matter in an open channel flow

“…While the first distribution type has been modelled by simple semi-empirical means [1,2,10,11,19,24], then the mathematical models of the second distribution type have required a more thorough physical reasoning. The Prandtl mixing length conception and the k−ε-type turbulence models [5,11,15,17,23] have been applied for this purpose hitherto. Unlike the quoted approaches applying traditional methods of the turbulence problem discussion, the current paper utilizes the theory of the rotationally anisotropic turbulence (RAT theory) [6].…”