scholarly journals Establishing the conditions for the formation of a near-wall layer of solid granular fill of a rotating drum

2021 ◽  
Vol 5 (1(113)) ◽  
pp. 51-61
Author(s):  
Yuriy Naumenko ◽  
Kateryna Deineka ◽  
Tamara Myronenko
Keyword(s):  
Wall Layer ◽  
Hydrodynamic Characteristics ◽  
Hydrodynamic Effect ◽  
Rotating Drum ◽  
Circulation Flow ◽  
Dynamic Motion ◽  
Layer Mode ◽  
Granular Fill ◽  
Degree Of Filling ◽  
Near Wall

This paper reports the assessment of the influence of dynamic motion parameters on the formation and disappearance at the cylindrical surface of the chamber of the rotating drum of the near-wall layer of non-loose granular fill. Based on the results of experimental visualization of the flow, the effect of solidity on the behavior of granular fill was revealed. The hydrodynamic effect of fill quasi-liquefaction under the action of solidity has been established, which involves the occurrence of a connecting interaction between adjacent layers and the surface of the chamber. Conversion of shear circulation flow to homogeneous dense clustered stream with slipping and rolling without relative movement of particles was detected. The hydrodynamic characteristics of circulation flow transition to the near-wall layer mode during rotation acceleration have been defined. Such a transition is implemented by smoothly increasing the thickness of the layer when the rest of the fill is circulated at the bottom of the chamber. The effect of the rheological hysteresis of the movement of the rotating chamber fill, caused by quasi-liquefaction of non-loose granular environment, has been established. The effect implies exceeding the speed limit ωfl in the formation of a near-wall layer, at rotation acceleration, above the boundary ωdl of the layer disappearance when the rotation slows down. The manifestation of hysteresis mainly increases with an increase in Reynolds number. The intensity of increased hysteresis manifestation increases with a decrease in the degree of filling the chamber. The value of the Froud number for the ωfl and ωdl boundaries increases with the increase in Re. It has been established that at the relative particle size of the dispersed fill ψdc≈(0.065–1.04)·10‑3 and Re=30–500, Fr=1–2.9, for the ωfl boundary, and Fr=0.5–1.4, for the ωdl boundary. The Fr value for the ωfl limit was found to exceed this value for the ωdl boundary by 1.6–2.1 times. The established effects make it possible to substantiate the rational parameters for the grinding process in drum-roll mills

Simulating flow separation from continuous surfaces: routes to overcoming the Reynolds number barrier

2009 ◽  
Vol 367 (1899) ◽  
pp. 2885-2903 ◽  
Author(s):  
Michael Leschziner ◽  
Ning Li ◽  
Fabrizio Tessicini
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Major Elements ◽  
Wall Layer ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Models ◽  
High Reynolds ◽  
Near Wall

This paper provides a discussion of several aspects of the construction of approaches that combine statistical (Reynolds-averaged Navier–Stokes, RANS) models with large eddy simulation (LES), with the objective of making LES an economically viable method for predicting complex, high Reynolds number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail: one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

scholarly journals Liposome Drug Delivery System across Endothelial Plasma Membrane: Role of Distance between Endothelial Cells and Blood Flow Rate

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1875
Author(s):  
Olga E. Glukhova
Keyword(s):  
Drug Delivery ◽  
Endothelial Cells ◽  
Blood Flow ◽  
Drug Release ◽  
Drug Delivery System ◽  
Delivery System ◽  
Small Diameter ◽  
Movement Pattern ◽  
Wall Layer ◽  
Near Wall

This paper discusses specific features of the interactions of small-diameter liposomes with the cytoplasmic membrane of endothelial cells using in silico methods. The movement pattern of the liposomal drug delivery system was modeled in accordance with the conditions of the near-wall layer of blood flow. Our simulation results show that the liposomes can become stuck in the intercellular gaps and even break down when the gap is reduced. Liposomes stuck in the gaps are capable of withstanding a shell deformation of ~15% with an increase in liposome energy by 26%. Critical deformation of the membrane gives an impetus to drug release from the liposome outward. We found that the liposomes moving in the near-wall layer of blood flow inevitably stick to the membrane. Liposome sticking on the membrane is accompanied by its gradual splicing with the membrane bilayer. This leads to a gradual drug release inside the cell.

Instability in a viscous flow driven by streamwise vortices

2001 ◽  
Vol 432 ◽  
pp. 127-166 ◽  
Author(s):  
K. W. BRINCKMAN ◽  
J. D. A. WALKER
Keyword(s):  
Boundary Layer ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Wall Layer ◽  
External Flow ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Wall Flow ◽  
Turbulent Wall ◽  
Near Wall

Unsteady separation processes at large finite, Reynolds number, Re, are considered, as well as the possible relation to existing descriptions of boundary-layer separation in the limit Re → ∞. The model problem is a fundamental vortex-driven three-dimensional flow, believed to be relevant to bursting near the wall in a turbulent boundary layer. Bursting is known to be associated with streamwise vortex motion, but the vortex/wall interactions that drive the near-wall flow toward breakdown have not yet been fully identified. Here, a simulation of symmetric counter-rotating vortices is used to assess the influence of sustained pumping action on the development of a viscous wall layer. The calculated solutions describe a three-dimensional flow at finite Re that is independent of the streamwise coordinate and consists of a crossflow plane motion, with a developing streamwise flow. The unsteady problem is constructed to mimic a typical cycle in turbulent wall layers and numerical solutions are obtained over a range of Re. Recirculating eddies develop rapidly in the near-wall flow, but these eddies are eventually bisected by alleyways which open up from the external flow region to the wall. At sufficiently high Re, an oscillation was found to develop in the streamwise vorticity field near the alleyways with a concurrent evolution of a local spiky behaviour in the wall shear. Above a critical value of Re, the oscillation grows rapidly in amplitude and eventually penetrates the external flow field, suggesting the onset of an unstable wall-layer breakdown. Local zones of severely retarded streamwise velocity are computed which are reminiscent of the low-speed streaks commonly observed in turbulent boundary layers. A number of other features also bear a resemblance to observed coherent structure in the turbulent wall layer.

Visualization of crystallization processes in the near-wall layer of a water drop

2013 ◽  
Vol 56 (3) ◽  
pp. 271-274 ◽  
Author(s):  
I. N. Pavlov ◽  
B. S. Rinkevichyus ◽  
A. V. Tolkachev
Keyword(s):  
Water Drop ◽  
Wall Layer ◽  
Near Wall

The minimal flow unit in near-wall turbulence

1991 ◽  
Vol 225 ◽  
pp. 213-240 ◽  
Author(s):  
Javier Jiménez ◽  
Parviz Moin
Keyword(s):  
Wall Stress ◽  
Wall Layer ◽  
Flow Unit ◽  
Wall Turbulence ◽  
Longitudinal Vortex ◽  
Spanwise Direction ◽  
Wall Region ◽  
Low Velocity ◽  
Good Agreement ◽  
Near Wall

Direct numerical simulations of unsteady channel flow were performed at low to moderate Reynolds numbers on computational boxes chosen small enough so that the flow consists of a doubly periodic (in x and z) array of identical structures. The goal is to isolate the basic flow unit, to study its morphology and dynamics, and to evaluate its contribution to turbulence in fully developed channels. For boxes wider than approximately 100 wall units in the spanwise direction, the flow is turbulent and the low-order turbulence statistics are in good agreement with experiments in the near-wall region. For a narrow range of widths below that threshold, the flow near only one wall remains turbulent, but its statistics are still in fairly good agreement with experimental data when scaled with the local wall stress. For narrower boxes only laminar solutions are found. In all cases, the elementary box contains a single low-velocity streak, consisting of a longitudinal strip on which a thin layer of spanwise vorticity is lifted away from the wall. A fundamental period of intermittency for the regeneration of turbulence is identified, and that process is observed to consist of the wrapping of the wall-layer vorticity around a single inclined longitudinal vortex.

1556 Experimental Study on a Three-Dimensional Wall Jet : Properties of the Near-wall Layer

2007 ◽  
Vol 2007.2 (0) ◽  
pp. 203-204
Author(s):  
Yoshihiro INOUE ◽  
Takaaki NISHIZUKA ◽  
Haruhisa YANO ◽  
Shintaro YAMASHITA
Keyword(s):  
Experimental Study ◽  
Three Dimensional ◽  
Wall Layer ◽  
Wall Jet ◽  
Near Wall

PECULIARITIES OF SHOWING CAPILLARY EFFECTS BY ELECTRORHEOLOGICAL FLUIDS

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1388-1394 ◽  
Author(s):  
E. V. KOROBKO ◽  
R. G. GORODKIN ◽  
M. I. MARDOSEVICH ◽  
E. I. MARDOSEVICH ◽  
A. O. KOROBKO
Keyword(s):  
Mineral Oil ◽  
Wall Layer ◽  
Electrorheological Fluids ◽  
Electrical Field ◽  
Electrical Fields ◽  
Capillary Effects ◽  
Wall Area ◽  
Weight Concentration ◽  
Near Wall

Experimentally the filling of a single capillary-condenser in the transverse to the gradient of electrical field current was studied. ERF on the basis of polymethyloxane fluids or mineral oil that consist of activated particles of SiO 2 with the weight concentration 5-30% were observed. The dependence of position of meniscus, its crookedness and the height of near-wall layer on the tension of electrical influence and time were measured. The variants of usage of homogeneous and gradient on the axis of the capillary electrical fields were studied. In the experiments consolidation of the middle area of meniscus and lengthening of its near-wall area and also the change of the speed of its filling while the intensity of electrical influence increased was found.

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