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Article

Experimental investigation of laminar and turbulent displacement of residual oil film

Zhang, Y., Barrouillet, B. and Skadsem, H.J.

2023Scientific Reports1321120

Keywordscleaning, flow displacement, shear flow, thin film

DisciplinesChemical Engineering, Fluid Mechanics, Mechanical Engineering

CategoryLaboratory experiments

Scale1e-6 to 1e-3 m / 1 to 60 s

Non-expert summaryThis paper reports an experimental study of the removal of thin oil films from the wall of a cylindrical tube by a flow of water. The removal of the oil film is measured by monitoring dye concentration in the flushing liquid leaving the system: local extents of removal were not measured. The authors investigated the effect of the flow regime of the displacing fluid (water Reynolds numbers ranged from 1480 to 12690), the duration of the displacing fluid flow, and the estimated wall shear stress imposed on the film. When the volume of fluid is limited, the largest displacement efficiency was observed at Re = 7000-8000 (named the intermediate turbulent regime). The largest Reynolds number flows were most effective for achieving complete cleaning over a long time period.

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Article

Numerical investigation of ice pigging isothermal flow in water-supply pipelines cleaning

Hu, J. and Tao, T.

2022Chemical Engineering Research & Design182428-437

Keywordscleaning, detachment, flow displacement, heat transfer, hydrodynamics, multiphase flow

DisciplinesChemical Engineering, Fluid Mechanics

CategoryNumerical simulations

Scale1e-3 to 1 m / 1e-3 to 1 s, 1 to 60 s

Non-expert summaryIce-pigging is a cleaning method in which a dense slurry (to be removed) is pushed along a channel (often a pipe, but more complex geometries can also be cleaned by this method) by an upstream solid-liquid thick ice slurry. The authors use the commercial CFD code FLUENT to evaluate a numerical model of this multiphase (solid-liquid) material undergoing pipe flow. In this coupled Eulerian-Eulerian description the two phases are treated separately as continuous phases coupled by pressure and interphase forces. They validate their model against experimental data from literature and report the predicted ice volume fraction, wall shear stress and melting rate. The results show strong inhomogeneity in the solid content (ice volume fraction).

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Article

Shear flow over a protuberance on a plane wall

Pozrikidis, C.

1997Journal of Engineering Mathematics3129-42

Keywordsdecontamination, flow displacement, shear flow

DisciplinesApplied Mathematics, Fluid Mechanics

CategoryNumerical simulations

Non-expert summaryMany cleaning and decontamination operations employ a flow to detach or move a particle or foreign element (e.g. a piece of dust, baterium or a spore) from a surface. The presence of the element disturbs the flow near the wall. Knowledge of the flow field and the forces imposed on the element is useful for predicting or quantifying removal. This paper considers a simple shear flow of a Newtonian fluid over an axisymmetric protuberance (with uniform shape) on a plane wall. The full 3-D problem is formulated in terms of three scalar Fredholm integral equations of the first kind and is solved using a boundary-element method. The hydrodynamic force and torque exerted on the protuberance, and distribution of shear stresses, are calculated. There is good agreement with previous analytical computations for hemi-spherical and spherical shapes.

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Article

Lift, drag and added mass of a hemispherical bubble sliding and growing on a wall in a viscous linear shear flow

Legendre, D., Colin, C., Coquard, T.

2008Phil. Trans. R. Soc. A3662233-2248

Keywordsflow displacement, shear flow

DisciplinesFluid Mechanics

CategoryNumerical simulations

Non-expert summaryThe Navier-Stokes equations for the three-dimensional flow of a Newtonian fluid around a hemispherical bubble simultaneously sliding along a flat wall and growing are solved. The forces experienced by the bubble (lift, drag and added mass) are calculated for bubble Reynolds numbers greater than or equal to 0.01 and flow Reynolds numbers < 2000. The bubble does not change shape. The scenarios studied are (i) an immobile bubble in a linear shear flow; (ii) a bubble sliding along the wall in an otherwise stagnant fluid; and (iii) a bubble sliding in a linear shear flow. The results are presented in the form of dimensionless coefficients.

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Article

A three-dimensional computer model analysis of three hypothetical biofilm detachment mechanisms

Chambless, J.D., Stewart, P.S.

2007Biotechnology and Bioengineering97(6)1573-1584

Keywordsbacteria, biofilm, cleaning, detachment, flow displacement, shear flow

DisciplinesChemical Engineering, Microbiology

CategoryNumerical simulations

Scale1e-6 m, 1e-6 to 1e-3 m, 1e-3 m / 1e-3 to 1 s, 1 to 60 s, 1 to 60 min

Non-expert summaryThe removal of biofilms by sloughing is a natural phenomenon in biofilm dynamics. Three hypothetical mechanisms of detachment were incorporated into a 3D model of biofilm development. The model integrated processes of substrate utilization, substrate diffusion, growth, cell advection, and detachment in a cellular automata framework. The three detachment mechanisms analyzed represented various physical and biological influences hypothesized to affect biofilm detachment; fluid shear removing protruding material; removal linked to local nutrient availability; and erosion. The detachment mechanisms demonstrated diverse behaviors with respect to the four analysis criteria. The results show that detachment is a critical determinant of biofilm structure and of the dynamics of biofilm accumulation and loss.

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Review article

Instabilities in blistering

Juel, A., Pihler-Puzović, D., Heil, M.

2018Annual Review of Fluid Mechanics50691-714

Keywordscavity flow, decontamination, elasticity theory, fingering instabilities, flow displacement, flow-structure interaction, Hele-Shaw flows, interfacial dynamics, lubrication theory, pattern formation

DisciplinesFluid Mechanics, Physics

CategoryReview

Scale1e-9 to 1e-6 m, 1e-6 m, 1e-6 to 1e-3 m / 1e-3 to 1 s, 1 to 60 s

Non-expert summaryThis is a review of the fluid mechanics associated with blistering, which occurs when a thin solid layer locally separates from an underlying substrate through cracking of a bulk material, delamination of a composite material, or peeling of a thin layer (membrane) adhered to the substrate by a thin layer of viscous fluid. The focus of the review is on the latter case, where the expansion of the newly formed blister by fluid injection occurs via a displacement flow, which peels the adhered surfaces apart through a two-way interaction between flow and deformation. These blisters are prone to fluid- and solid-mechanical instabilities. If the injected fluid is less viscous than the fluid already occupying the gap, patterns of short and stubby fingers (fingering) form on the propagating fluid interface. Buckling/wrinkling instabilities of the delaminated layer can arise for sufficiently thin membranes and can interact with the fluid mechanical fingering instability.

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Article

Pressure-driven miscible two-fluid channel flow with density gradients

Sahu, K.C., Ding, H., Valluri, P., Matar, O.K.

2009Physics of Fluids21043603

Keywordscleaning, flow displacement, hydrodynamics, miscible liquids, multiphase flow

DisciplinesChemical Engineering, Fluid Mechanics

CategoryNumerical simulations

Non-expert summaryThe displacement of one liquid by another in a channel of constant height occurs in flushing and cleaning operations. The authors study the effect of buoyancy (arising from different fluid densities) on a pressure-driven flow of two miscible fluids in inclined channels using direct numerical simulations DNS). The flow dynamics are governed by the continuity and Navier–Stokes equations, without the Boussinesq approximation for buoyancy, coupled to a convective-diffusion equation for mass transfer between the two liquids. The effect of concentration on viscosity and density is modelled. The effect of varying the density ratio, Froude number, and channel inclination on the flow dynamics is examined, for moderate Reynolds numbers. These detailed simulations give insights into mixing and cleaning behaviour.

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Article

Linear stability analysis and numerical simulation of miscible two-layer channel flow

Sahu, K.C., Ding, H., Valluri, P., Matar, O.K.

2009Physics of Fluids21042104

Keywordscleaning, flow displacement, interfacial dynamics, linear stability analysis, miscible liquids, multiphase flow

DisciplinesChemical Engineering, Fluid Mechanics

CategoriesNumerical simulations, Theoretical modelling

Non-expert summaryWhen one liquid is pumped into a channel containing a second liquid, the behaviour depends on the properties of the two fluids and pressure driving force. This paper considers the stability of a flow of two miscible fluids in a horizontal channel. The flow dynamics are governed by the continuity and Navier–Stokes equations, with mass transfer between the two. An analysis of the flow in the linear regime delineates the presence of convective and absolute instabilities, and shows that vertical gradients of viscosity perturbations (caused by mixing) are the main destabilizing influence of the interface (in agreement with previous work). Previous work in the area is reviewed as well. Transient numerical simulations demonstrate the development of complex dynamics in the nonlinear regime, characterized by roll-up phenomena and intense convective mixing.

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Article

Self-cleaning of a hydrophobic surface by a rolling water droplet

Hassan, G., Yilbas, B.S., Al-Sharafi, A., Al-Qahtani, H.

2019Scientific Reports95744

Keywordscleaning, drop, flow displacement, wetting

DisciplinesMechanical Engineering, Surface Chemistry

CategoriesLaboratory experiments, Theoretical modelling

Scale1e-6 to 1e-3 m, 1e-3 m, 1e-3 to 1 m / 1e-3 to 1 s, 1 to 60 s

Non-expert summaryThis is an experimental study of removal of dust particles from a hydrophobic surface by a rolling/sliding water droplet. The effect of surface inclination angle on droplet dynamics and dust removal is analyses and compared with a model. Droplet rolling dominates over sliding. Removal is mainly due to the droplet liquid coating the particles as it passes over the particle, and the removal efficiency is determined by the inclination of the surface.

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Article

Transient displacement of a viscoplastic material by air in straight and suddenly constricted tubes

Dimakopoulos, Y., Tsamopoulos, J.

2003J. Non-Newtonian Fluid Mech.11243-75

Keywordscleaning, flow displacement, moving boundary problem, viscoplastic fluid

DisciplinesChemical Engineering, Fluid Mechanics

CategoryNumerical simulations

Non-expert summaryThe flushing of a viscous fluid from a pipe or cavity by a less viscous one is widely used in cleaning operations. This paper reports the numerical modelling of the transient displacement of a viscoplastic material from straight or suddenly constricted (square entry) concentric cylindrical tubes of finite length, simulating a gas at higher pressure displacing the geometry initially filled with liquid. A mixed finite element method is coupled with a quasi-elliptic mesh generation scheme in order to follow the very large deformations involved. The gas bubble grows in length and leaves a thin liquid film on the duct wall (so it does not remove all the liquid). The shape of the bubble is computed for various Reynolds and Bingham numbers (ratio of yield stress to viscous stress). The 'tip splitting' instability that can arise in flow of a gas along a tube filled with a viscous Newtonian fluids is suppressed with viscoplastic fluids at higher Bingham numbers. The shape of the bubble as it passes through the constriction is also studied.

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Article

On the gas-penetration in straight tubes completely filled with a viscoelastic fluid

Dimakopoulos, Y., Tsamopoulos, J.

2004J. Non-Newtonian Fluid Mechanics117(2-3)117-139

Keywordscleaning, flow displacement

DisciplinesApplied Mathematics, Fluid Mechanics

CategoryNumerical simulations

Non-expert summaryThe use of a gas to purge a viscous liquid from a straight cylindrical pipe of finite length is investigated for the case where the liquid is viscoelastic. The rheology of the liquid is described using the Giesekus and the Phan-Thien-Tanner (PTT) models. The focus of the work is on the numerical aspects of the simulations. A parametric analysis is made in order to determine the effects of elastic and inertial forces, and the Newtonian viscosity, on the process.

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Article

Transient displacement of Newtonian and viscoplastic liquids by air in complex tubes

Dimakopoulos, Y., Tsamopoulos, J.

2007J. Non-Newtonian Fluid Mechanics142(1-3)162-182

Keywordscleaning, flow displacement, hydrodynamics, multiphase flow, viscoplastic fluid

DisciplinesApplied Mathematics, Fluid Mechanics

CategoriesNumerical simulations, Theoretical modelling

Non-expert summaryThe use of pressurised air to displace a viscoplastic liquid from a complex duct geometry is simulated using detailed numerical modelling. The transient displacement of Newtonian and viscoplastic liquids by air in cylindrical tubes of finite length with a concentric expansion followed by a contraction in their cross section is considered. The change in diameter is not sudden. Various expansion and contraction ratios are studied. Papanastasiou's formula is employed to regularize the discontinuous Bingham model. Results are presented for a range of fluid and geometrical parameters, and some cases are compared to analytical results.

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