Elastic particle deformation in rectangular channel flow as a measure of particle stiffness

Soft Matter ◽  
2018 ◽  
Vol 14 (2) ◽  
pp. 216-227 ◽  
Author(s):  
Margaret Y. Hwang ◽  
Seo Gyun Kim ◽  
Heon Sang Lee ◽  
Susan J. Muller
Keyword(s):  
Shear Modulus ◽  
Channel Flow ◽  
Rectangular Channel ◽  
Particle Deformation ◽  
Experimental Deformation ◽  
Soft Particles ◽  
Elastic Particle ◽  
Confined Channel

Experimental deformation of hydrogel soft particles in a confined channel is quantified and can be used to obtain shear modulus.

Frictional Drag Reduction: Review and Numerical Simulation of Microbubble Drag Reduction in a Channel Flow

2018 ◽  
Vol Vol 160 (A2) ◽  
Author(s):  
S Sindagi ◽  
R Vijayakumar ◽  
B K Saxena
Keyword(s):  
Numerical Simulation ◽  
Drag Reduction ◽  
Channel Flow ◽  
Void Fraction ◽  
Rectangular Channel ◽  
Air Injection ◽  
Spanwise Direction ◽  
Flat Plates ◽  
Frictional Drag ◽  
Injection Point

The reduction of ship’s resistance is one of the most effective way to reduce emissions, operating costs and to improve EEDI. It is reported that, for slow moving vessels, the frictional drag accounts for as much as 80% of the total drag, thus there is a strong demand for the reduction in the frictional drag. The use of air as a lubricant, known as Micro Bubble Drag Reduction, to reduce that frictional drag is an active research topic. The main focus of authors is to present the current scenario of research carried out worldwide along with numerical simulation of air injection in a rectangular channel. Latest developments in this field suggests that, there is a potential reduction of 80% & 30% reduction in frictional drag in case of flat plates and ships respectively. Review suggests that, MBDR depends on Gas or Air Diffusion which depends on, Bubble size distributions and coalescence and surface tension of liquid, which in turn depends on salinity of water, void fraction, location of injection points, depth of water in which bubbles are injected. Authors are of opinion that, Microbubbles affect the performance of Propeller, which in turn decides net savings in power considering power required to inject Microbubbles. Moreover, 3D numerical investigations into frictional drag reduction by microbubbles were carried out in Star CCM+ on a channel for different flow velocities, different void fraction and for different cross sections of flow at the injection point. This study is the first of its kind in which, variation of coefficient of friction both in longitudinal as well as spanwise direction were studied along with actual localised variation of void fraction at these points. From the study, it is concluded that, since it is a channel flow and as the flow is restricted in confined region, effect of air injection is limited to smaller area in spanwise direction as bubbles were not escaping in spanwise direction.

A numerical analysis of vortex shedding within a confined channel flow

1999 ◽  
Vol 213 (5) ◽  
pp. 477-490 ◽  
Author(s):  
T. J. Scanlon ◽  
M. T. Stickland ◽  
A Oldroyd
Keyword(s):  
Numerical Analysis ◽  
Channel Flow ◽  
Vortex Shedding ◽  
Convective Transport ◽  
Fully Implicit ◽  
Order Scheme ◽  
Computational Fluid Dynamics Cfd ◽  
Vortex Shedding Frequency ◽  
Higher Order Scheme ◽  
Confined Channel

The numerical analysis of two-dimensional laminar vortex shedding from a rectangular cylinder within a confined channel flow is presented. This study, carried out using a computational fluid dynamics (CFD) code based on the SIMPLEST algorithm, considers the influence of numerical diffusion on the prediction of the vortex shedding frequency. The computational analysis compares the commonly used first-order accurate UPWIND scheme with the well-known third-order scheme QUICK and its derivative SMART, used for the discretization of convective transport. For the temporal differencing, a fully implicit scheme has been adopted. Plots of Strouhal number against Reynolds number suggest that the implementation of a higher-order scheme is beneficial for the accurate capture of the vortex shedding transient in unsteady flows of this nature.

scholarly journals Interplay of inertia and deformability on rheological properties of a suspension of capsules

2014 ◽  
Vol 751 ◽  
pp. 725-745 ◽  
Author(s):  
Timm Krüger ◽  
Badr Kaoui ◽  
Jens Harting
Keyword(s):  
Three Dimensional ◽  
Reynolds Numbers ◽  
Particle Collision ◽  
Immersed Boundary ◽  
Lateral Migration ◽  
Particle Deformation ◽  
Substantial Impact ◽  
Inertia Effects ◽  
Focusing Effect ◽  
Soft Particles

AbstractThe interplay of inertia and deformability has a substantial impact on the transport of soft particles suspended in a fluid. However, to date a thorough understanding of these systems is still missing, and only a limited number of experimental and theoretical studies are available. We combine the finite-element, immersed-boundary and lattice-Boltzmann methods to simulate three-dimensional suspensions of soft particles subjected to planar Poiseuille flow at finite Reynolds numbers. Our findings confirm that the particle deformation and inclination increase when inertia is present. We observe that the Segré–Silberberg effect is suppressed with respect to the particle deformability. Depending on the deformability and strength of inertial effects, inward or outward lateral migration of the particles takes place. In particular, for increasing Reynolds numbers and strongly deformable particles, a hitherto unreported distinct flow focusing effect emerges, which is accompanied by a non-monotonic behaviour of the apparent suspension viscosity and thickness of the particle-free layer close to the channel walls. This effect can be explained by the behaviour of a single particle and the change of the particle collision mechanism when both deformability and inertia effects are relevant.

scholarly journals Experimental dataset and numerical simulation of floating bodies transport in open-channel flow

2020 ◽  
Vol 22 (5) ◽  
pp. 1161-1181
Author(s):  
Elisabetta Persi ◽  
Gabriella Petaccia ◽  
Stefano Sibilla ◽  
Pilar Brufau ◽  
José Ignacio García-Palacin
Keyword(s):  
Channel Flow ◽  
Water Surface ◽  
Open Channel ◽  
Numerical Models ◽  
Rectangular Channel ◽  
Open Channel Flow ◽  
Body Motion ◽  
Lagrangian Model ◽  
Floating Body ◽  
Floating Bodies

Abstract Numerical models trying to faithfully represent the movement of floating bodies transport in open-channel flow require experimental data for validation. In order to provide an adequate dataset, flume experiments were carried out to analyse the transport of singular and grouped rigid bodies floating on the water surface. Both cylindrical and spherical samples were employed: they were released in a rectangular channel under steady conditions in one-dimensional (plain channel) and two-dimensional (2D) configurations using one rectangular side obstacle, one smooth side obstacle or two rectangular alternate obstacles. The outcomes of the experiments are the planar displacement and the rotation of the samples, which are related to the flow field in the different configurations. The detailed experimental analysis of the floating body motion provides information for the calibration of numerical models simulating floating bodies transport. This dataset is thus employed for the validation of the Eulerian–Lagrangian model ORSA2D_WT, highlighting its strengths and improvable aspects. Similar applications could be carried out with any 2D model which performs the simulation of discrete elements moving on the water surface.

scholarly journals Photosensitised heterogeneous oxidation kinetics of biomass burning aerosol surrogates by ozone using an irradiated rectangular channel flow reactor

2013 ◽  
Vol 13 (3) ◽  
pp. 7553-7598
Author(s):  
S. M. Forrester ◽  
D. A. Knopf
Keyword(s):  
Channel Flow ◽  
Biomass Burning ◽  
Ozone Concentration ◽  
Flow Reactor ◽  
Rectangular Channel ◽  
Radiative Properties ◽  
Photon Flux ◽  
Biomass Burning Aerosol ◽  
Visible Irradiation ◽  
Uptake Data

Abstract. Heterogeneous reaction kinetics involving organic aerosol and atmospheric oxidants such as ozone can be enhanced under visible or UV irradiation in the presence of a photosensitiser, with subsequent implications for the climate, cloud radiative properties, air quality, and source appointment. In this study we report the steady state reactive uptake coefficient, γ, of O3 by levoglucosan and 5-nitroguaiacol acting as surrogates for biomass burning aerosol particles, with and without the presence of Pahokee peat acting as a photosensitiser. The reactive uptake has been determined in the dark and as a function of visible and UV-A irradiation and ozone concentration. In addition, γ was determined for 1:1, 1:10, and 1:100 by mass mixtures of Pahokee peat and 5-nitroguaiacol, and for a 10:1:3 mixture of levoglucosan, Pahokee peat, and 5-nitroguaiacol. We developed a novel irradiated rectangular channel flow reactor (I-RCFR) that was operated under low pressures of about 2–4 hPa, and allowed for uniform irradiation of the organic substrates. The I-RCFR was coupled to a chemical ionisation mass spectrometer and has been successfully validated by measuring the kinetics between various organic species and oxidants. γ of O3 and levoglucosan in the dark and under visible and UV-A irradiation was determined to be in the range of (2–11) × 10−6 and did not change in the presence of Pahokee peat. The determined γ of O3 and 5-nitroguaiacol in the dark was 5.7 × 10−6 and was only enhanced under UV-A irradiation, yielding a value of 3.6 × 10−5. γ of the 1:1 Pahokee peat/5-nitroguaiacol substrate was enhanced under visible and UV-A irradiation to 2.4 × 10−5 and 2.8 × 10−5, respectively. Decreasing the amount of Pahokee peat in the 5-nitroguaiacol/Pahokee peat substrate resulted in lower values of γ under visible irradiation, however, γ was consistent under UV-A irradiation regardless of the amount of Pahokee peat. The 10:1:3 mixture by mass of levoglucosan, Pahokee peat, and 5-nitroguaiacol, under both visible and UV-A irradiation yielded γ values of 2.8 × 10−5 and 1.4 × 10−5, respectively. γ was determined as a function of photon flux for O3 with the 1:1 Pahokee peat/5-nitroguaiacol substrate, yielding a linear relationship under both visible and UV-A irradiation. γ of O3 with the 1:1 Pahokee peat/5-nitroguaiacol substrate was determined as a function of ozone concentration and exhibited an inverse dependence of γ on ozone concentration, commonly interpreted as a Langmuir-Hinshelwood mechanism. The reactive uptake data have been represented by a Langmuir-type isotherm. From the O3 uptake data under visible irradiation, the following fit parameters have been derived: ks = (5.5 ± 2.7) × 10−19 cm2 s−1 molecule−1 and KO3 = (2.3 ± 2.0) × 10−12 cm3 molecule−1 and under UV-A irradiation: ks = (8.1 ± 2.0) × 10−19 cm2 s−1 molecule−1 and KO3 = (1.7 ± 0.7) × 10−12 cm3 molecule−1. The oxidative power, or the product of γ and [O3], was determined for O3 with the 1:1 Pahokee peat/5-nitroguaiacol substrate and was in the range of (1.2–26) × 106 molecule cm−3. Atmospheric particle lifetimes were estimated for a 0.4 μm 5-nitroguaiacol particle as a function of visible and UV-A irradiation and ozone concentration.

Sign in / Sign up

Export Citation Format

Share Document