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Spatial distribution and settling velocity of heavy particles in synthetic turbulent ﬁelds

100%

Łuniewski M. , Pozorski J.

tom nr 135

87--100

We analyse numerically the motion of small inertial particles, subject to gravity, in two simple velocity ﬁelds: two-dimensional cellular ﬂow, and a three-dimensional ﬂow being the superposition of random Fourier velocity modes. The latter, also known as the kinematic simulation or synthetic turbulence, has often been applied in various studies, including those aiming to predict particle dispersion. The interplay of the particle inertia and the acceleration of gravity has non-trivial consequences for trajectories of particles and their spatial distribution, known as a preferential concentration. Also, we compute the average settling velocity of particles in function of their inertia and the number of ﬂuid velocity modes used in simulations. The present paper aims to study these efects, as the synthetic turbulence represents an interesting option for subﬁlter modeling in particle-laden large-eddy simulation.

Pollution sources and metallic elements mobility recorded by heavy minerals in soils affected by Cu-smelting (Legnica, SW Poland)

88%

Tyszka R. , Pietranik A. , Marciniak-Maliszewska B. , Kierczak J.

Mineralogia

2024

tom Vol. 55, iss. 1

1--14

Heavy mineral particles are widely used in Earth science studies to show sediment provenance and weathering conditions. Such particles are particularly useful in polluted soils surrounding mining and smelting facilities because heavy minerals are common by-products of these activities and may accumulate in the soils. As such, the particles are suitable indicators of metallic element carriers and their stability in the soil environment. In this study, we analyze heavy mineral particles in two soils surrounding the active copper smelter (Legnica, SW, Poland). We show that particles associated with different smelting activities dominate the heavy mineral fraction. We note the general absence of sulfides in the fraction indicating that these minerals might have been entirely dissolved, but timing of this dissolution is uncertain (before or after deposition within soils). Currently, the carriers of potentially toxic elements are mainly secondary Fe oxides. Studies aiming at better estimation of the proportion of metallic elements contained in heavy mineral particles are needed to fully use the potential of these phases in polluted soil studies. We estimate that Pb contained in Pb-rich silicate glass constitutes.

Prędkość opadania ciężkiej cząstki w polu burzliwym

63%

Nowosielski J.

Inżynieria Chemiczna i Procesowa

2001

tom T. 22, z. 3D

1025--1030

Rozważono opadanie ciężkiej cząstki w płynie burzliwym. Stwierdzono, że stosowane powszechnie wzory do obliczeń czasu relaksacji cząstki nie są właściwe. Gdy opadanie odbywa się poza zakresem Stokesa, wartość czasu relaksacji dla przemieszczania się cząstki w kierunku zgodnym z działaniem siły zewnętrznej jest inna niż w kierunku prostopadłym, zaś rozkład składowej prędkości cząstki jest niesymetryczny, co wynika z nieliniowej zależności siły oporu od prędkości względem płynu.

Falling of a heavy particle in turbulent fluid apart from Stokes law was considered. It was shown the relaxation time for the longitudinal dispersion differs from the value of the parameter for the transverse displacement of the particle. The distribution of the particle fluctuating velocity in the direction parallel to the external force is asymmetric because of the non-linear dependence of the drag force on the slip velocity.