scholarly journals A linearised model for calculating inertial forces on a particle in the presence of a permeate flow

2018 ◽  
Vol 861 ◽  
pp. 253-274 ◽  
Author(s):  
Mike Garcia ◽  
B. Ganapathysubramanian ◽  
S. Pennathur
Keyword(s):  
Axial Flow ◽  
Reynolds Numbers ◽  
Lateral Force ◽  
Inertial Particles ◽  
Inertial Forces ◽  
Viscous Forces ◽  
Lateral Forces ◽  
Biological Studies ◽  
Wide Range ◽  
Time Required

Understanding particle transport and localisation in porous channels, especially at moderate Reynolds numbers, is relevant for many applications ranging from water reclamation to biological studies. Recently, researchers experimentally demonstrated that the interplay between axial and permeate flow in a porous microchannel results in a wide range of focusing positions of finite-sized particles (Garcia & Pennathur, Phys. Rev. Fluids, vol. 2 (4), 2017, 042201). We numerically explore this interplay by computing the lateral forces on a neutrally buoyant spherical particle that is subject to both inertial and permeate forces over a range of experimentally relevant particle sizes and channel Reynolds numbers. Interestingly, we show that the lateral forces on the particle are well represented using a linearised model across a range of permeate-to-axial flow rate ratios. Specifically, our model linearises the effects of the permeate flow, which suggests that the interplay between axial and permeate flow on the lateral force on a particle can be represented as a superposition between the lateral (inertial) forces in pure axial flow and the viscous forces in pure permeate flow. We experimentally validate this observation for a range of flow conditions. The linearised behaviour observed significantly reduces the complexity and time required to predict the migration of inertial particles in permeate channels.

Film spreading from a miscible drop on a deep liquid layer

2017 ◽  
Vol 829 ◽  
pp. 304-327 ◽  
Author(s):  
Raj Dandekar ◽  
Anurag Pant ◽  
Baburaj A. Puthenveettil
Keyword(s):  
Surface Tension ◽  
Water Layer ◽  
Reynolds Numbers ◽  
Capillary Waves ◽  
Water Mixture ◽  
Inertial Forces ◽  
Viscous Forces ◽  
Dimensionless Velocity ◽  
Deep Water Layer ◽  
Film Spreading

We study the spreading of a film from ethanol–water droplets of radii $0.9~\text{mm}<r_{d}<1.1~\text{mm}$ on the surface of a deep water layer for various concentrations of ethanol in the drop. Since the drop is lighter ($\unicode[STIX]{x1D709}=\unicode[STIX]{x1D70C}_{l}/\unicode[STIX]{x1D70C}_{d}>1.03$), it stays at the surface of the water layer during the spreading of the film from the drop; the film is more viscous than the underlying water layer since $\unicode[STIX]{x1D712}=\unicode[STIX]{x1D707}_{l}/\unicode[STIX]{x1D707}_{d}>0.38$. Inertial forces are not dominant in the spreading since the Reynolds numbers based on the film thickness $h_{f}$ are in the range $0.02<Re_{f}<1.4$. The spreading is surface-tension-driven since the film capillary numbers are in the range $0.0005<Ca_{f}<0.0069$ and the drop Bond numbers are in the range $0.19<Bo_{d}<0.56$. We observe that, when the drop is brought in contact with the water surface, capillary waves propagate from the point of contact, followed by a radially expanding, thin circular film of ethanol–water mixture. The film develops instabilities at some radius to form outward-moving fingers at its periphery while it is still expanding, till the expansion stops at a larger radius. The film then retracts, during which time the remaining major part of the drop, which stays at the centre of the expanding film, thins and develops holes and eventually mixes completely with water. The radius of the expanding front of the film scales as $r_{f}\sim t^{1/4}$ and shows a dependence on the concentration of ethanol in the drop as well as on $r_{d}$, and is independent of the layer height $h_{l}$. Using a balance of surface tension and viscous forces within the film, along with a model for the fraction of the drop that forms the thin film, we obtain an expression for the dimensionless film radius $r_{f}^{\ast }=r_{f}/r_{d}$, in the form $fr_{f}^{\ast }={t_{\unicode[STIX]{x1D707}d}^{\ast }}^{1/4}$, where $t_{\unicode[STIX]{x1D707}d}^{\ast }=t/t_{\unicode[STIX]{x1D707}d}$, with the time scale $t_{\unicode[STIX]{x1D707}d}=\unicode[STIX]{x1D707}_{d}r_{d}/\unicode[STIX]{x0394}\unicode[STIX]{x1D70E}$ and $f$ is a function of $Bo_{d}$. Similarly, we show that the dimensionless velocity of film spreading, $Ca_{d}=u_{f}\unicode[STIX]{x1D707}_{d}/\unicode[STIX]{x0394}\unicode[STIX]{x1D70E}$, scales as $4f^{4}Ca_{d}={r_{f}^{\ast }}^{-3}$.

Rotating Cavity With Axial Throughflow of Cooling Air: Flow Structure

1990 ◽  
Author(s):  
P. R. Farthing ◽  
C. A. Long ◽  
J. M. Owen ◽  
J. R. Pincombe
Keyword(s):  
Flow Structure ◽  
Vortex Breakdown ◽  
Laser Doppler Anemometry ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Angular Speed ◽  
Rotating Cavity ◽  
Wide Range ◽  
Ekman Layers ◽  
Cooling Air

A rotating cavity with an axial throughflow of cooling air is used to provide a simplified model for the flow that occurs between adjacent corotating compressor discs inside a gas-turbine engine. Flow visualization and laser-Doppler anemometry are employed to study the flow structure inside isothermal and heated rotating cavities for a wide range of axial-gap ratios. G. rotational. Reynolds numbers, Reφ, axial Reynolds numbers, Rez, and temperature distributions. For the isothermal case, the superposed axial flow of air generates a powerful toroidal vortex inside cavities with large gap ratios (G > 0.400) and weak counter-rotating toroidal vortices for cavities with small gap ratios. Depending on the gap ratio and the Rossby number, ε (where ε ∝ Rez/Reφ), axisymmetric and nonaxisymmetric vortex breakdown can occur, but circulation inside the cavity becomes weaker as ε is reduced. For the case where one or both discs of the cavity are heated, the flow becomes nonaxisymmetric: cold air enters the cavity in a “radial arm” on either side of which is a vortex. The cyclonic and anti-cyclonic circulations inside the two vortices are presumed to create the circumferential pressure gradient necessary for the air to enter the cavity (in the radial arm) and to leave (in Ekman layers on the discs). The core of fluid between the Ekman layers precesses with an angular speed close to that of the discs, and vortex breakdown appears to reduce the relative speed of precession.

Laboratory Rearing of the Seed-corn Maggot, Hylemya cilicrura (Rond.) (Diptera: Anthomyiidae)

1958 ◽  
Vol 90 (6) ◽  
pp. 372-374 ◽  
Author(s):  
R. J. McClanahan ◽  
L. A. Miller
Keyword(s):  
Fish Meal ◽  
Adult Stage ◽  
High Protein Diet ◽  
Laboratory Rearing ◽  
Seed Corn ◽  
Biological Studies ◽  
Wide Range ◽  
Laboratory Investigations ◽  
Successive Generations ◽  
Time Required

The seed-corn maggot, Hylemya cilicrura (Rond.), is a cosmopolitan pest and feeds on a wide range of hosts. The maggots cause extensive damage to seeds and seedlings of beans, soybeans, peas, corn, and cucurbits. Hitherto laboratory investigations have been hampered because the maggot has been very difficult to rear continuously.Biological studies have indicated that such diverse diets as soybeans (Harukawa et al., 1934), cottonseed meal and fish meal (Reid, 1940), and potato (Leach, 1926) serve to rear the maggot to the adult stage. However, it has been difficult to maintain an adult colony for the time required for mating and oviposition. Reid (1940) used field-collected flies as a source of eggs in his experiments, but failed to get a second generation. Successive generations were reared by Ristich (1950), who provided a high protein diet for adults held in glass cages; in attempts to follow this method at Chatham, only one complete generation could be reared. A more satisfactory method of rearing the species continuously is described in this paper.

scholarly journals Experimental observation of the origin and structure of elastoinertial turbulence

2021 ◽  
Vol 118 (45) ◽  
pp. e2102350118
Author(s):  
George H. Choueiri ◽  
Jose M. Lopez ◽  
Atul Varshney ◽  
Sarath Sankar ◽  
Björn Hof
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Shear Layers ◽  
Viscoelastic Flows ◽  
Inertial Forces ◽  
Weakly Nonlinear ◽  
Weakly Nonlinear Theory ◽  
Wide Range ◽  
Maximum Drag Reduction ◽  
Striking Contrast

Turbulence generally arises in shear flows if velocities and hence, inertial forces are sufficiently large. In striking contrast, viscoelastic fluids can exhibit disordered motion even at vanishing inertia. Intermediate between these cases, a state of chaotic motion, “elastoinertial turbulence” (EIT), has been observed in a narrow Reynolds number interval. We here determine the origin of EIT in experiments and show that characteristic EIT structures can be detected across an unexpectedly wide range of parameters. Close to onset, a pattern of chevron-shaped streaks emerges in qualitative agreement with linear and weakly nonlinear theory. However, in experiments, the dynamics remain weakly chaotic, and the instability can be traced to far lower Reynolds numbers than permitted by theory. For increasing inertia, the flow undergoes a transformation to a wall mode composed of inclined near-wall streaks and shear layers. This mode persists to what is known as the “maximum drag reduction limit,” and overall EIT is found to dominate viscoelastic flows across more than three orders of magnitude in Reynolds number.

Microwaves: Application in Electron Microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 140-141
Author(s):  
Anthony S-Y Leong ◽  
David W Gove
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Chemical Reactions ◽  
Electromagnetic Waves ◽  
Tissue Fixation ◽  
Primary Method ◽  
Dipolar Molecules ◽  
Wide Range ◽  
Time Required ◽  
Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

TIME TO THE END OF PRIMARY CONSOLIDATION (EOP) OF SOFT CLAYEY SOILS: CONCERNING THE EFFECT OF ATTERBERG’S LIMIT AND CYCLIC LOADING HISTORY

2019 ◽  
Vol 128 (2B) ◽  
pp. 29-41
Author(s):  
Trần Thanh Nhàn
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Clayey Soils ◽  
Loading History ◽  
Cyclic Shear ◽  
Wide Range ◽  
Primary Consolidation ◽  
Time Required

In order to observe the end of primary consolidation (EOP) of cohesive soils with and without subjecting to cyclic loading, reconstituted specimens of clayey soils at various Atterberg’s limits were used for oedometer test at different loading increments and undrained cyclic shear test followed by drainage with various cyclic shear directions and a wide range of shear strain amplitudes. The pore water pressure and settlement of the soils were measured with time and the time to EOP was then determined by different methods. It is shown from observed results that the time to EOP determined by 3-t method agrees well with the time required for full dissipation of the pore water pressure and being considerably larger than those determined by Log Time method. These observations were then further evaluated in connection with effects of the Atterberg’s limit and the cyclic loading history.

New insights on Laminaria digitata ultrastructure through combined conventional chemical fixation and cryofixation

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Christos Katsaros ◽  
Sophie Le Panse ◽  
Gillian Milne ◽  
Carl J. Carrano ◽  
Frithjof Christian Küpper
Keyword(s):  
Cell Wall ◽  
General Structure ◽  
Raw Material ◽  
Rocky Shores ◽  
Chemical Fixation ◽  
Laminaria Digitata ◽  
Vegetative Cells ◽  
Biological Studies ◽  
New Findings ◽  
Wide Range

Abstract The objective of the present study is to examine the fine structure of vegetative cells of Laminaria digitata using both chemical fixation and cryofixation. Laminaria digitata was chosen due to its importance as a model organism in a wide range of biological studies, as a keystone species on rocky shores of the North Atlantic, its use of iodide as a unique inorganic antioxidant, and its significance as a raw material for the production of alginate. Details of the fine structural features of vegetative cells are described, with particular emphasis on the differences between the two methods used, i.e. conventional chemical fixation and freeze-fixation. The general structure of the cells was similar to that already described, with minor differences between the different cell types. An intense activity of the Golgi system was found associated with the thick external cell wall, with large dictyosomes from which numerous vesicles and cisternae are released. An interesting type of cisternae was found in the cryofixed material, which was not visible with the chemical fixation. These are elongated structures, in sections appearing tubule-like, close to the external cell wall or to young internal walls. An increased number of these structures was observed near the plasmodesmata of the pit fields. They are similar to the “flat cisternae” found associated with the forming cytokinetic diaphragm of brown algae. Their possible role is discussed. The new findings of this work underline the importance of such combined studies which reveal new data not known until now using the old conventional methods. The main conclusion of the present study is that cryofixation is the method of choice for studying Laminaria cytology by transmission electron microscopy.

Turbulent three-dimensional dielectric electrohydrodynamic convection between two plates

2012 ◽  
Vol 696 ◽  
pp. 228-262 ◽  
Author(s):  
A. Kourmatzis ◽  
J. S. Shrimpton
Keyword(s):  
Spatial Data ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Energy Budgets ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Wide Range ◽  
Scalar Variance

AbstractThe fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low (${\mathit{Re}}_{E} = 1$) and high electric Reynolds numbers (up to ${\mathit{Re}}_{E} = 120$). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\ensuremath{\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\ensuremath{\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC; however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.

scholarly journals Focusing of Particles in a Microchannel with Laser Engraved Groove Arrays

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 263
Author(s):  
Tianlong Zhang ◽  
Yigang Shen ◽  
Ryota Kiya ◽  
Dian Anggraini ◽  
Tao Tang ◽  
...  
Keyword(s):  
Open Space ◽  
Lateral Displacement ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Particle Sedimentation ◽  
Nanoparticle Separation ◽  
Wide Range ◽  
Fs Laser ◽  
Channel Bottom ◽  
Myoblast Cells

Continuous microfluidic focusing of particles, both synthetic and biological, is significant for a wide range of applications in industry, biology and biomedicine. In this study, we demonstrate the focusing of particles in a microchannel embedded with glass grooves engraved by femtosecond pulse (fs) laser. Results showed that the laser-engraved microstructures were capable of directing polystyrene particles and mouse myoblast cells (C2C12) towards the center of the microchannel at low Reynolds numbers (Re < 1). Numerical simulation revealed that localized side-to-center secondary flows induced by grooves at the channel bottom play an essential role in particle lateral displacement. Additionally, the focusing performance proved to be dependent on the angle of grooves and the middle open space between the grooves based on both experiments and simulation. Particle sedimentation rate was found to critically influence the focusing of particles of different sizes. Taking advantage of the size-dependent particle lateral displacement, selective focusing of micrometer particles was demonstrated. This study systematically investigated continuous particle focusing in a groove-embedded microchannel. We expect that this device will be used for further applications, such as cell sensing and nanoparticle separation in biological and biomedical areas.

scholarly journals A proposal to determine the distribution of lateral forces from loaded recycled plastic drainage kerbs

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Fin O’Flaherty ◽  
Fathi Al-Shawi
Keyword(s):  
Laboratory Test ◽  
Detailed Analysis ◽  
Test Data ◽  
Lateral Force ◽  
Measuring Device ◽  
Test Methodology ◽  
Lateral Forces ◽  
Test Conditions ◽  
Fit For Purpose ◽  
Construction Product

AbstractThis study presents a detailed analysis of the lateral forces generated as a result of vertically applied loads to recycled plastic drainage kerbs. These kerbs are a relatively new addition to road infrastructure projects. When concrete is used to form road drainage kerbs, its deformation is minimum when stressed under heavy axle loads. Although recycled plastic kerbs are more environmentally friendly as a construction product, they are less stiff than concrete and tend to deform more under loading leading to a bursting type, lateral force being applied to the haunch materials, the magnitude of which is unknown. A method is proposed for establishing the distribution of these lateral forces resulting from deformation under laboratory test conditions. A load of 400 kN is applied onto a total of six typical kerbs in the laboratory in accordance with the test standard. The drainage kerbs are surrounded with 150 mm of concrete to the front and rear haunch and underneath as is normal during installation. The lateral forces exerted on the concrete surround as a result of deformation of the plastic kerbs are determined via a strain measuring device. Analysis of the test data allows the magnitude of the lateral forces to the surrounding media to be determined and, thereby, ensuring the haunch materials are not over-stressed as a result. The proposed test methodology and subsequent analysis allows for an important laboratory-based assessment of any typical recycled plastic drainage kerbs to be conducted to ensure they are fit-for-purpose in the field.

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