scholarly journals Migration and Alignment of Three Interacting Particles in Poiseuille Flow of Giesekus Fluids

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 218
Author(s):  
Bing-Rui Liu ◽  
Jian-Zhong Lin ◽  
Xiao-Ke Ku
Keyword(s):  
Poiseuille Flow ◽  
Particle Diameter ◽  
Cross Flow ◽  
Weissenberg Number ◽  
Channel Height ◽  
Interacting Particles ◽  
Fictitious Domain Method ◽  
Particle Spacing ◽  
Mobility Parameter ◽  
Direct Forcing

Effect of rheological property on the migration and alignment of three interacting particles in Poiseuille flow of Giesekus fluids is studied with the direct-forcing fictitious domain method for the Weissenberg number (Wi) ranging from 0.1 to 1.5, the mobility parameter ranging from 0.1 to 0.7, the ratio of particle diameter to channel height ranging from 0.2 to 0.4, the ratio of the solvent viscosity to the total viscosity being 0.3 and the initial distance (y0) of particles from the centerline ranging from 0 to 0.2. The results showed that the effect of y0 on the migration and alignment of particles is significant. The variation of off-centerline (y0 ≠ 0) particle spacing is completely different from that of on-centerline (y0 = 0) particle spacing. As the initial vertical distance y0 increased, the various types of particle spacing are more diversified. For the off-centerline particle, the change of particle spacing is mainly concentrated in the process of cross-flow migration. Additionally, the polymer extension is proportional to both the Weissenberg number and confinement ratio. The bigger the Wi and confinement ratio is, the bigger the increment of spacing is. The memory of shear-thinning is responsible for the reduction of d1. Furthermore, the particles migrate abnormally due to the interparticle interaction.

An Efficient Immersed Boundary Method Based on Penalized Direct Forcing for Simulating Flows Through Real Porous Media

2012 ◽  
Author(s):  
Wim-Paul Breugem ◽  
Vincent van Dijk ◽  
René Delfos
Keyword(s):  
Porous Medium ◽  
Ct Scan ◽  
Immersed Boundary Method ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Particle Diameter ◽  
Immersed Boundary ◽  
Average Particle ◽  
Boundary Method ◽  
Direct Forcing

A computationally efficient Immersed Boundary Method (IBM) based on penalized direct forcing was employed to determine the permeability of a real porous medium. The porous medium was composed of about 9000 glass beads with an average particle diameter of 1.93 mm and a porosity of 0.367. The forcing of the IBM depends on the local solid volume fraction within a computational grid cell. The latter could be obtained from a high-resolution X-ray Computed Tomography (CT) scan of the packing. An experimental facility was built to determine the permeability of the packing experimentally. Numerical simulations were performed for the same packing based on the data from the CT scan. For a scan resolution of 0.1 mm the numerical value for the permeability was nearly 70% larger than the experimental value. An error analysis indicated that the scan resolution of 0.1 mm was too coarse for this packing.

Assessment of Cooling Enhancement of Synthetic Jet in Conjunction With Forced Convection

2007 ◽  
Author(s):  
Yogen Utturkar ◽  
Mehmet Arik ◽  
Mustafa Gursoy
Keyword(s):  
Forced Convection ◽  
Cross Flow ◽  
Electronics Cooling ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Channel Height ◽  
Large Area ◽  
Complete Replacement ◽  
Cooling Enhancement ◽  
The Impact

Synthetic jets are meso or micro fluidic devices, which operate on the “zero-net-mass-flux” principle. They impart a positive net momentum flux to the external environment, and are able to produce the cooling effect of a fan sans its ducting, reliability issues, and oversized dimensions. As a result, recently their application as electronics cooling devices is gaining momentum. Traditionally, synthetic jets have been sought as a replacement to the fan in many electronic devices. However, in certain large applications, complete replacement of the fan is not feasible, because it is necessary to provide the basic level of cooling over a large area of a printed assembly board. Such applications often pose a question whether synthetic jet would be able to locally provide reasonable enhancement over the forced convection of the fan flow. In the present study, we present the cooling performance of synthetic jets complementing forced convection from a fan. Both experiments and CFD computations are performed to investigate the interaction of the jet flowfield with a cross flow from fan. The inlet velocity, jet disk amplitude, and channel height are varied in the computational simulations to evaluate the impact of these changes on the cooling properties. Overall, both studies show that a synthetic jet is able to pulse and disrupt the boundary layer caused from fan flow, and improve heat transfer up to 4× over forced convection.

A two-dimensional-three-component model for spanwise rotating plane Poiseuille flow

2019 ◽  
Vol 880 ◽  
pp. 478-496 ◽  
Author(s):  
Shengqi Zhang ◽  
Zhenhua Xia ◽  
Yipeng Shi ◽  
Shiyi Chen
Keyword(s):  
Reynolds Number ◽  
Poiseuille Flow ◽  
Reynolds Shear Stress ◽  
Streamwise Velocity ◽  
Channel Height ◽  
Neutral Stability ◽  
Two Dimensional ◽  
Plane Poiseuille Flow ◽  
Rotation Numbers ◽  
3C Model

Spanwise rotating plane Poiseuille flow (RPPF) is one of the canonical flow problems to study the effect of system rotation on wall-bounded shear flows and has been studied a lot in the past. In the present work, a two-dimensional-three-component (2D/3C) model for RPPF is introduced and it is shown that the present model is equivalent to a thermal convection problem with unit Prandtl number. For low Reynolds number cases, the model can be used to study the stability behaviour of the roll cells. It is found that the neutral stability curves, critical eigensolutions and critical streamfunctions of RPPF at different rotation numbers ($Ro$) almost collapse with the help of a rescaling with a newly defined Rayleigh number $Ra$ and channel height $H$. Analytic expressions for the critical Reynolds number and critical wavenumber at different $Ro$ can be obtained. For a turbulent state with high Reynolds number, the 2D/3C model for RPPF is self-sustained even without extra excitations. Simulation results also show that the profiles of mean streamwise velocity and Reynolds shear stress from the 2D/3C model share the same linear laws as the fully three-dimensional cases, although differences on the intercepts can be observed. The contours of streamwise velocity fluctuations behave like plumes in the linear law region. We also provide an explanation to the linear mean velocity profiles observed at high rotation numbers.

Experiments on the lift and drag of spheres suspended in a Poiseuille flow

1964 ◽  
Vol 20 (3) ◽  
pp. 513-527 ◽  
Author(s):  
R. Eichhorn ◽  
S. Small
Keyword(s):  
Reynolds Number ◽  
Poiseuille Flow ◽  
Rotation Speed ◽  
Fluid Dynamic ◽  
Particle Diameter ◽  
Dynamic Forces ◽  
Shear Parameter ◽  
Fluid Properties ◽  
Approach Velocity ◽  
Lift And Drag

An experimental investigation of the fluid dynamic forces on spheres suspended in a Poiseuille flow was performed. Small spheres of polystyrene, nylon, and Lucite, having diameters ranging from 0.061 in. to 0.126 in. were suspended in Poiseuille flows in a 0.419 in. diameter tube. Variations in particle size and density, the fluid properties, and the angle of inclination of the tube, resulted in a sphere Reynolds number (based on particle diameter and approach velocity) ranging from 80 to 250. The results are presented as curves which include the coefficients of lift and drag, and the dimensionless rotation speed plotted versus Reynolds number and a dimensionless shear parameter.

Unconditional Linear Stability of Plane Couette-Poiseuille Flow in Presence of Cross Flow

2010 ◽  
Author(s):  
Anirban Guha ◽  
Ian A. Frigaard
Keyword(s):  
Reynolds Number ◽  
Linear Stability ◽  
Poiseuille Flow ◽  
Energy Production ◽  
Energy Analysis ◽  
Cross Flow ◽  
Base Flow ◽  
Lower Range ◽  
Long Wavelength ◽  
Flow Reynolds Number

We have investigated the linear stability of plane Couette-Poiseuille flow in the presence of a cross-flow. The base flow is characterised by the cross flow Reynolds number, Ri and the dimensionless wall velocity, k. Corresponding to each k ∈ [0,1], we have observed two ranges of Ri for which the flow is unconditionally linearly stable. In the lower range, we have a stabilisation of long wavelengths leading to a cut-off Ri. In this range, cross-flow stabilisation and Couette stabilisation appear to act via very similar mechanisms in this range, leading to the potential for robust compensatory design of flow stabilisation using either mechanism. As Ri is increased, we see first destabilisation and then stabilisation at very large Ri. The instability is again a long wavelength mechanism. A linear energy analysis reveals that in this range the Reynolds stress becomes amplified, the critical layer is irrelevant and viscous dissipation is completely dominated by the energy production/negation, which approximately balances at criticality.

scholarly journals Quantifying Concentration Polarization – Raman Microspectroscopy for In-Situ Measurement in a Flat Sheet Cross-flow Nanofiltration Membrane Unit

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Oliver Jung ◽  
Florencia Saravia ◽  
Michael Wagner ◽  
Stefan Heißler ◽  
Harald Horn
Keyword(s):  
Concentration Polarization ◽  
Cross Flow ◽  
Raman Microspectroscopy ◽  
Channel Height ◽  
Concentration Profiles ◽  
Operating Pressure ◽  
Membrane Unit ◽  
Lower Velocity ◽  
Flat Sheet

Abstract In this work, the concentration polarization layer (CPL) of sulphate in a cross-flow membrane system was measured in-situ using Raman microspectroscopy (RM). The focus of this work is to introduce RM as a new tool for the study of mass transfer inside membrane channels in reverse osmosis (RO) and nanofiltration (NF) generally. Specifically, this work demonstrates how to use RM for locally resolved measurement of sulphate concentration in a cross-flow flat-sheet NF membrane flow cell with channel dimensions similar to commonly applied RO/NF spiral wound modules (channel height about 0.7 mm). Concentration polarization profiles of an aqueous magnesium sulphate solution of 10 gsulphate·L−1 were obtained at operating pressure of 10 bar and cross-flow velocities of 0.04 and 0.2 m·s−1. The ability of RM to provide accurate concentration profiles is discussed thoroughly. Optical effects due to refraction present one of the main challenges of the method by substantially affecting signal intensity and depth resolution. The concentration profiles obtained in this concept study are consistent with theory and show reduced CPL thickness and membrane wall concentration with increasing cross-flow velocity. The severity of CP was quantified to reach almost double the bulk concentration at the lower velocity.

On the patterns of interaction between shear and interfacial modes in plane air–water Poiseuille flow

2005 ◽  
Vol 461 (2057) ◽  
pp. 1583-1597 ◽  
Author(s):  
Evgeniy Shapiro ◽  
Sergei Timoshin
Keyword(s):  
Poiseuille Flow ◽  
Neutral Curve ◽  
Interfacial Instability ◽  
Stable Region ◽  
Channel Height ◽  
Water Layers ◽  
Tollmien Schlichting ◽  
Neutral Conditions ◽  
Patterns Of Interaction ◽  
Interfacial Mode

The current work deals with the numerical analysis of linear stability problems in a stratified plain Poiseuille flow of air over water with equal layer heights. The interaction and branch exchange between Tollmien–Schlichting instability in air and interfacial instability is discovered and investigated. This effect is shown to stabilize disturbances with wavelengths of the order of channel height for interfacial waves and to produce a closed stable region inside the neutral curve of the interfacial mode. The behaviour of three unstable modes in the problem, corresponding to Tollmien–Schlichting type instability in air and water layers and interfacial instability respectively, has been studied in detail. Neutral conditions for all three modes and the stable region have been calculated.

scholarly journals Modal and non-modal stability analysis of electrohydrodynamic flow with and without cross-flow

2015 ◽  
Vol 770 ◽  
pp. 319-349 ◽  
Author(s):  
Mengqi Zhang ◽  
Fulvio Martinelli ◽  
Jian Wu ◽  
Peter J. Schmid ◽  
Maurizio Quadrio
Keyword(s):  
Stability Analysis ◽  
Electric Field ◽  
Linear Stability ◽  
Poiseuille Flow ◽  
Cross Flow ◽  
Transient Growth ◽  
Unstable Flow ◽  
Electrohydrodynamic Flow ◽  
Stability Threshold ◽  
Energy Growth

We report the results of a complete modal and non-modal linear stability analysis of the electrohydrodynamic flow for the problem of electroconvection in the strong-injection region. Convective cells are formed by the Coulomb force in an insulating liquid residing between two plane electrodes subject to unipolar injection. Besides pure electroconvection, we also consider the case where a cross-flow is present, generated by a streamwise pressure gradient, in the form of a laminar Poiseuille flow. The effect of charge diffusion, often neglected in previous linear stability analyses, is included in the present study and a transient growth analysis, rarely considered in electrohydrodynamics, is carried out. In the case without cross-flow, a non-zero charge diffusion leads to a lower linear stability threshold and thus to a more unstable flow. The transient growth, though enhanced by increasing charge diffusion, remains small and hence cannot fully account for the discrepancy of the linear stability threshold between theoretical and experimental results. When a cross-flow is present, increasing the strength of the electric field in the high-$\mathit{Re}$Poiseuille flow yields a more unstable flow in both modal and non-modal stability analyses. Even though the energy analysis and the input–output analysis both indicate that the energy growth directly related to the electric field is small, the electric effect enhances the lift-up mechanism. The symmetry of channel flow with respect to the centreline is broken due to the additional electric field acting in the wall-normal direction. As a result, the centres of the streamwise rolls are shifted towards the injector electrode, and the optimal spanwise wavenumber achieving maximum transient energy growth increases with the strength of the electric field.

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