scholarly journals Particle Accumulation Structures in a 5 cSt Silicone Oil Liquid Bridge: New Data for the Preparation of the JEREMI Experiment

2021 ◽  
Vol 33 (2) ◽  
Author(s):  
Paolo Capobianchi ◽  
Marcello Lappa
Keyword(s):  
Liquid Bridge ◽  
Silicone Oil ◽  
Fluid Dynamic ◽  
Solid Particles ◽  
Critical Threshold ◽  
Marangoni Flow ◽  
Disk Radius ◽  
Carrier Fluid ◽  
Aspect Ratios ◽  
Time Periodic

AbstractSystems of solid particles in suspension driven by a time-periodic flow tend to create structures in the carrier fluid that are reminiscent of highly regular geometrical items. Within such a line of inquiry, the present study provides numerical results in support of the space experiments JEREMI (Japanese and European Research Experiment on Marangoni flow Instabilities) planned for execution onboard the International Space Station. The problem is tackled by solving the unsteady non-linear governing equations for the same conditions that will be established in space (microgravity, 5 cSt silicone oil and different aspect ratios of the liquid bridge). The results reveal that for a fixed supporting disk radius, the dynamics are deeply influenced by the height of the liquid column. In addition to its expected link with the critical threshold for the onset of instability (which makes Marangoni flow time-periodic), this geometrical parameter can have a significant impact on the emerging waveform and therefore the topology of particle structures. While for shallow liquid bridges, pulsating flows are the preferred mode of convection, for tall floating columns the dominant outcome is represented by rotating fluid-dynamic disturbance. In the former situation, particles self-organize in circular sectors bounded internally by regions of particle depletion, whereas in the latter case, particles are forced to accumulate in a spiral-like structure. The properties of some of these particle attractors have rarely been observed in earlier studies concerned with fluids characterized by smaller values of the Prandtl number.

Electrohydrodynamic stability: Taylor–Melcher theory for a liquid bridge suspended in a dielectric gas

2002 ◽  
Vol 452 ◽  
pp. 163-187 ◽  
Author(s):  
C. L. BURCHAM ◽  
D. A. SAVILLE
Keyword(s):  
Surface Tension ◽  
Dielectric Constant ◽  
Electric Fields ◽  
Liquid Bridge ◽  
Numerical Solutions ◽  
Specific Conductivity ◽  
Axisymmetric Deformation ◽  
Aspect Ratios ◽  
The Stability ◽  
Theory And Experiment

A liquid bridge is a column of liquid, pinned at each end. Here we analyse the stability of a bridge pinned between planar electrodes held at different potentials and surrounded by a non-conducting, dielectric gas. In the absence of electric fields, surface tension destabilizes bridges with aspect ratios (length/diameter) greater than π. Here we describe how electrical forces counteract surface tension, using a linearized model. When the liquid is treated as an Ohmic conductor, the specific conductivity level is irrelevant and only the dielectric properties of the bridge and the surrounding gas are involved. Fourier series and a biharmonic, biorthogonal set of Papkovich–Fadle functions are used to formulate an eigenvalue problem. Numerical solutions disclose that the most unstable axisymmetric deformation is antisymmetric with respect to the bridge’s midplane. It is shown that whilst a bridge whose length exceeds its circumference may be unstable, a sufficiently strong axial field provides stability if the dielectric constant of the bridge exceeds that of the surrounding fluid. Conversely, a field destabilizes a bridge whose dielectric constant is lower than that of its surroundings, even when its aspect ratio is less than π. Bridge behaviour is sensitive to the presence of conduction along the surface and much higher fields are required for stability when surface transport is present. The theoretical results are compared with experimental work (Burcham & Saville 2000) that demonstrated how a field stabilizes an otherwise unstable configuration. According to the experiments, the bridge undergoes two asymmetric transitions (cylinder-to-amphora and pinch-off) as the field is reduced. Agreement between theory and experiment for the field strength at the pinch-off transition is excellent, but less so for the change from cylinder to amphora. Using surface conductivity as an adjustable parameter brings theory and experiment into agreement.

A Model for the Effect of Velocity on Erosion of N80 Steel Tubing due to the Normal Impingement of Solid Particles

1992 ◽  
Vol 114 (1) ◽  
pp. 54-64 ◽  
Author(s):  
D. P. Chase ◽  
E. F. Rybicki ◽  
J. R. Shadley
Keyword(s):  
Solid Particle ◽  
Computational Study ◽  
Target Material ◽  
Target Surface ◽  
American Petroleum Institute ◽  
Solid Particles ◽  
Unknown Coefficient ◽  
Conservation Of Energy ◽  
Carrier Fluid ◽  
Erosion Behavior

As part of a combined experimental and computational study of erosion for gas and oil production conditions, a semi-empirical model has been developed to predict erosion ratio behaviors of metals due to solid particle impingement. One use of the model will be to reduce the total number of experiments needed to characterize erosion behavior. The model represents material property information associated with both the target material and the impinging particles, as well as impingement speed. Five different models are examined in terms of ability to predict erosion ratio behavior as a function of impingement speed. The model selected is based on a conservation of energy formulation and fracture mechanics considerations to predict the amount of material removed due to solid particle impingement. The resulting equation to predict the erosion ratio for a given particle size contains one unknown coefficient which is determined through comparison with experimental data. Illustrative examples are presented for data for two different sizes of glass bead solid particles in an oil carrier fluid impinging on an API (American Petroleum Institute) N80 grade steel target at an impingement angle 90 deg to the target surface. Using erosion data at one impingement speed to determine the unknown coefficient, the model was used to predict erosion behavior at a range of other speeds. Good agreement between the erosion ratio data and the values predicted by the model were found for two solid particle sizes. Recommendations for expanding the capabilities of the model are pointed out.

scholarly journals Two-Phase Dusty Fluid Flow Along a Rotating Axisymmetric Round-Nosed Body

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Sadia Siddiqa ◽  
Naheed Begum ◽  
M. A. Hossain ◽  
Rama Subba Reddy Gorla
Keyword(s):  
Boundary Layer ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Solid Particles ◽  
Dust Particles ◽  
Computational Domain ◽  
Two Phase ◽  
Carrier Fluid ◽  
Boundary Layer Equations ◽  
Implicit Finite Difference

This article is concerned with the class of solutions of gas boundary layer containing uniform, spherical solid particles over the surface of rotating axisymmetric round-nosed body. By using the method of transformed coordinates, the boundary layer equations for two-phase flow are mapped into a regular and stationary computational domain and then solved numerically by using implicit finite difference method. In this study, a rotating hemisphere is used as a particular example to elucidate the heat transfer mechanism near the surface of round-nosed bodies. We will investigate whether the presence of dust particles in carrier fluid disturbs the flow characteristics associated with rotating hemisphere or not. A comprehensive parametric analysis is presented to show the influence of the particle loading, the buoyancy ratio parameter, and the surface of rotating hemisphere on the numerical findings. In the absence of dust particles, the results are graphically compared with existing data in the open literature, and an excellent agreement has been found. It is noted that the concentration of dust particles’ parameter, Dρ, strongly influences the heat transport rate near the leading edge.

Numerical simulation of wind loads on solar panels

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840009 ◽  
Author(s):  
Kao-Chun Su ◽  
Kung-Ming Chung ◽  
Shu-Tsung Hsu
Keyword(s):  
Fluid Dynamic ◽  
Pressure Coefficient ◽  
Solar Panel ◽  
Wind Loads ◽  
Strong Wind ◽  
Solar Panels ◽  
Wind Uplift ◽  
Aspect Ratios ◽  
Wind Tunnel Data ◽  
Inclined Angle

Solar panels mounted on the roof of a building or ground are often vulnerable to strong wind loads. This study aims to investigate wind loads on solar panels using computational fluid dynamic (CFD). The results show good agreement with wind tunnel data, e.g. the streamwise distribution of mean surface pressure coefficient of a solar panel. Wind uplift for solar panels with four aspect ratios is evaluated. The effect of inclined angle and clearance (or height) of a solar panel is addressed. It is found that wind uplift of a solar panel increases when there is an increase in inclined angle and the clearance above ground shows an opposite effect.

A numerical study of the nucleation, growth and settling of crystals from a turbulent convecting fluid

2021 ◽  
Author(s):  
Vojtech Patocka ◽  
Nicola Tosi ◽  
Enrico Calzavarini
Keyword(s):  
Magma Chamber ◽  
Solid Fraction ◽  
Large Scale ◽  
Solid Phase ◽  
Numerical Study ◽  
Equilibrium Concentration ◽  
Solid Particles ◽  
Settling Rate ◽  
Carrier Fluid ◽  
Nucleation Growth

<p>We evaluate the equilibrium concentration of a thermally convecting suspension that is cooled from above and in which<br>solid crystals are self-consistently generated in the thermal boundary layer near the top. In a previous study (Patočka et<br>al., 2020), we investigated the settling rate of solid particles suspended in a highly vigorous (Ra = 10<sup>8</sup> , 10<sup>10</sup>, and 10<sup>12</sup> ),<br>finite Prandtl number (Pr = 10, 50) convection. In this follow-up study we additionally employ the model of crystal<br>generation and growth of Jarvis and Woods (1994), instead of using particles with a predefined size and density that are<br>uniformly injected into the carrier fluid.</p><p>We perform a series of numerical experiments of particle-laden thermal convection in 2D and 3D Cartesian geometry<br>using the freely available code CH4 (Calzavarini, 2019). Starting from a purely liquid phase, the solid fraction gradually<br>grows until an equilibrium is reached in which the generation of the solid phase balances the loss of crystals due to<br>sedimentation at the bottom of the fluid. For a range of predefined density contrasts of the solid phase with respect to<br>the density of the fluid (ρ<sub>p</sub> /ρ<sub>f</sub> = [0, 2]), we measure the time it takes to reach such equilibrium. Both this time and<br>the equilibrium concentration depend on the average settling rate of the particles and are thus non-trival to compute for<br>particle types that interact with the large-scale circulation of the fluid (see Patočka et al., 2020).</p><p>We apply our results to the cooling of a large volume of magma, spanning from a large magma chamber up to a<br>global magma ocean. Preliminary results indicate that, as long as particle re-entrainment is not a dominant process, the<br>separation of crystals from the fluid is an efficient process. Fractional crystallization is thus expected and the suspended<br>solid fraction is typically small, prohibiting phenomena in which the feedback of crystals on the fluid begins to govern the<br>physics of the system (e.g. Sparks et al, 1993).</p><p>References<br>Patočka V., Calzavarini E., and Tosi N.(2020). Settling of inertial particles in turbulent Rayleigh-Bénard convection.<br>Physical Review Fluids, 26(4) 883-889.</p><p>Jarvis, R. A. and Woods, A. W.(1994). The nucleation, growth and settling of crystals from a turbulently convecting<br>fluid. J. Fluid. Mech, 273 83-107.</p><p>Sparks, R., Huppert, H., Koyaguchi, T. et al (1993). Origin of modal and rhythmic igneous layering by sedimentation in<br>a convecting magma chamber. Nature, 361, 246-249.</p><p>Calzavarini, E (2019). Eulerian–Lagrangian fluid dynamics platform: The ch4-project. Software Impacts, 1, 100002.</p>

scholarly journals Bio-Capture of Solid Pollutants by Vegetation Canopy Cave in Shallow Water Flow

2019 ◽  
Vol 16 (23) ◽  
pp. 4846 ◽  
Author(s):  
Yanhong Li ◽  
Liquan Xie ◽  
Tsung-chow Su
Keyword(s):  
Shallow Water ◽  
Water Flow ◽  
Removal Rate ◽  
Suspended Solid ◽  
Solid Particles ◽  
Capture Efficiency ◽  
Vegetation Canopy ◽  
Shallow Water Flow ◽  
Flume Experiments ◽  
Aspect Ratios

Vegetation has already been acknowledged to have the ability to remove fine solid pollutants by retention and absorption, and is widely used in the biorestoration engineering of natural shallow water flow. Vegetation usually takes a long time to obtain the expected removal rate. Therefore, vegetation is not applicable for some urgent or pressing situations. In addition, in traditional biorestoration engineering, solid pollutants usually deposit in the soil of flow bed, which infiltrates into the far-field and accumulates in crops to threaten human health. Herein, we propose a new biotechnique of foliage capture by designing a cave on the top of a vegetation canopy, which is aimed to enhance the removal efficiency (i.e., achieve quick removal) and avoid the soil deposition of pollutants. The effectiveness and efficiency of this new design were validated by a set of indoor water flume experiments, with one flat canopy top configuration serving as the model of a traditional bioretention system and three cave configurations of differing aspect ratios. The results showed that compared with that of the flat canopy top, the total amount of foliage-captured solid particles for the three caved canopies increased by 3.8, 7.3, and 12.2 times. Further, we found that the foliage-capture efficiency depended on the aspect ratio of the canopy cave. The results revealed that the effectiveness of foliage capture and the enhanced efficiency were mainly from three hydrodynamic mechanisms: (i) as flow penetrated the cave boundary from the above-canopy region to the within-canopy region, it entrained solid pollutants to collide with the foliage and increased their fate of capture; (ii) the large eddy vortices of turbulence broke due to the increasing canopy resistance, which resulted in enhanced mixing dynamics for fine, suspended, solid pollutants to collide into foliage; and (iii) the flow shear along the cave boundary decreased, which provided a reduced lift force for solid pollutants to suspend or resuspend. Comparisons between the flat canopy and caved canopies of three aspect ratios showed that the design of the canopy cave is highly significant for capture efficiency.

Attempt to study Marangoni flow of low-Pr-number fluids using a liquid bridge of silver

2008 ◽  
Vol 41 (12) ◽  
pp. 2107-2111 ◽  
Author(s):  
Taketoshi Hibiya ◽  
Keisuke Nagafuchi ◽  
Suguru Shiratori ◽  
Noriyoshi Yamane ◽  
Shumpei Ozawa
Keyword(s):  
Liquid Bridge ◽  
Marangoni Flow

Marangoni flow in half-zone liquid bridge of molten tin under ramped temperature difference

2005 ◽  
Vol 280 (3-4) ◽  
pp. 620-631 ◽  
Author(s):  
K. Li ◽  
S. Yasuhiro ◽  
N. Imaishi ◽  
S. Yoda
Keyword(s):  
Temperature Difference ◽  
Liquid Bridge ◽  
Marangoni Flow
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