Flow past a single stationary sphere, 1. Experimental and numerical techniques

Tiwari, Sudarshan; Pal, Eshita; Bale, Shivkumar; Minocha, Nitin; Patwardhan, Ashwin W.; Nandakumar, K.; Joshi, Jyeshtharaj B.

doi:10.1016/j.powtec.2019.01.037

Cited by 33 publications

(14 citation statements)

References 108 publications

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“…Similarly, amongst studies not examining plants, few researchers have documented the patterns of airflow over hemispheres or crescents (Cao and Tamura 2020;Kim and Baik 2003;Savory and Toy 1985;Tavakol et al 2015;Tavakol et al 2010). However, the airflow around spherical and cylindrical obstructions is well described (Achenbach 1974;Achenbach 1972;Breuer 2000;Breuer 1998;Constantinescu and Squires 2004;Dehbi and Martin 2011;Hoffman 2006;Lyotard et al 2007;Norberg 1987;Raithby and Eckert 1968;Tiwari et al 2020), and provides a framework to interpret flow around cushion plants. Indeed, it has been consistently observed that as free-stream air approaches a nonporous bluff (i.e.…”

Section: Modelling Airflow Using Computational Fluid Dynamicsmentioning

confidence: 99%

Wind and seed: a conceptual model of shape-formation in the cushion plant Azorella Selago

et al. 2020

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Aims The sub-Antarctic cushion plant, Azorella selago, is usually hemispherical when small but frequently crescent-shaped when larger. Spatial variation in wind speed and in air-borne seed and sediment deposition is examined to determine if wind scouring and deposition patterns could contribute to the development of non-hemispherical shapes in cushion plants. Methods Computational fluid dynamic analyses were conducted for hemispherical and crescent-shaped cushion plants parameterizing models with data from A. selago habitats on Marion Island. Numerical data were contextualized with field observations to arrive at a conceptual model for shape development. Results Airflow modelling showed that both wind scouring and seed deposition of the commonly co-occurring grass Agrostis magellanica are greater on the windward side of the plant. By contrast, heavier sediment particles are predominantly deposited on the leeward side of plants, leading to burial of lee-side A. selago stems. This sediment accumulation may initiate the development of the crescent-shape in hemispherical plants by increasing stem mortality on the plant’s leeward edge. Once developed, the crescent-shape is probably self-reinforcing because it generates greater air recirculation (and lower air velocities) which enhances further deposition and establishment of A. magellanica grasses in the lee of the crescent. The conceptual model consists therefore of three stages namely, (1) negligible air recirculation, (2) sediment deposition and grass establishment, and (3) differential cushion growth. Conclusion This conceptual model of plant shape development may explain the occurrence and orientation of crescent-shaped cushion plants and highlights how predicted changes in wind patterns may affect vegetation patterns.

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Section: Modelling Airflow Using Computational Fluid Dynamicsmentioning

confidence: 99%

Wind and seed: a conceptual model of shape-formation in the cushion plant Azorella Selago

et al. 2020

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“…CFD has been used as a useful tool for hydrodynamic prediction, design, scale‐up, and optimization of several chemical engineering equipments. Some of the commonly used chemical engineering equipments, that have investigated using CFD so as to understand the underlying flow physics involved are: pipes and pipe bends, particulate flows, packed bed reactors, fluidized bed reactors, bubbly flows, and heat exchangers . CFD has gained a lot of importance in the previous three decades owing to the wide application and promising results, which it offers at a nominal cost.…”

Section: Introductionmentioning

confidence: 99%

Teaching turbulent flow through pipe fittings using computational fluid dynamics approach

Gajbhiye

Kulkarni

Tiwari

et al. 2020

Engineering Reports

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The largest network of fluid transportation in the world is through pipelines.During the transportation of fluids through pipes, several "fittings" are used in the piping system such as elbows, T-junctions, reducers, expanders, bends, couplings, valves, etc. The flow complexities in pipe fittings are accounted for the pressure drop in piping network design. The pressure drop is estimated using the loss coefficient or equivalent length method using standard charts. Computational fluid dynamics (CFD) is a reliable tool to estimate pressure drop and understand nonidealities in pipe fittings. The use of CFD in the advanced level course in transport phenomena/fluid flow for piping network design can help students to implement modern mathematical tools as well as evaluate standard protocols followed in the industries. In this article, an interactive teaching methodology has been implemented to investigate the hydrodynamics in various pipe fittings (elbow, bend, Tee, and reducer) by actually visualizing the flow. The three-dimensional flow visualization is used to demonstrate the nonidealities such as separation, swirling, dead zones, etc. The CFD simulations of pipe fittings provided a new learning experience to the students that would help them to predict the pressure drops in industrial piping network systems. The outcome from the students' survey showed that the proposed CFD methodology assisted them to gain a better understanding of conventional Chemical Engineering subjects of "Transport Phenomena" and "Fluid Dynamics" in an innovative way. K E Y W O R D Scomputational fluid dynamics, head loss coefficient, pipe fittings, turbulence models 1

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“…Such phenomena are of particular interest regarding, for example, the study of microscale ocean geology 40 . This is especially true considering that current experimental techniques such as micro-Particle Image Velocimetry 41 and microscale synthetic schlieren 42 are limited to particle diameters above 10 to 150 µm, which are far larger than the particles observed in our study.…”

Section: Discussionmentioning

confidence: 70%

Synthesis of core–shell copper–graphite submicronic particles and carbon nano-onions by spark discharges in liquid hydrocarbons

Glad

Gorry

Suk

et al. 2021

Sci Rep

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Spark discharge in hydrocarbon liquids is considered a promising method for the synthesis of various nanomaterials, including nanocomposites. In this study, copper–carbon particles were synthesized by generating spark discharges between two Cu electrodes immersed in heptane, cyclohexane, or toluene. The synthesized particles were characterized using scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. Overall, two families of particles were observed: Cu particles (diameter < 10 nm) embedded in a carbon matrix and submicrometric Cu particles encapsulated in a carbon shell. The obtained results indicate that the size distribution of the Cu nanoparticles and the degree of graphitization of the carbon matrix depend on the liquid. Indeed, discharges in heptane lead to Cu particles with diameters of 2–6 nm embedded in a carbon matrix of low graphitization degree, while discharges in toluene result in particles with diameters of 2–14 nm embedded in carbon matrix of high graphitization degree. Based on the obtained experimental results, it is proposed that the Cu nanoparticles are produced in the plasma core where Cu (evaporated from the electrode surface) and carbonaceous species (decomposition of the liquid) are present. When the plasma hits the electrode surface, hot (thousands of Kelvin) Cu particles are ejected from the electrode, and they propagate in the liquid. The propagation of the hot particles in the liquid results in the local evaporation of this liquid, which leads to the formation of a C-shell around each Cu particle. In few cases where the shape of the Cu particle is not spherical, carbon nanoonions are detected between the C-shell and the Cu core. These nanoonions are supposedly formed under the effect of the fluid vortices generated close to the particle surfaces when these latter are ejected into the liquid.

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Flow past a single stationary sphere, 1. Experimental and numerical techniques

Cited by 33 publications

References 108 publications

Wind and seed: a conceptual model of shape-formation in the cushion plant Azorella Selago

Wind and seed: a conceptual model of shape-formation in the cushion plant Azorella Selago

Teaching turbulent flow through pipe fittings using computational fluid dynamics approach

Synthesis of core–shell copper–graphite submicronic particles and carbon nano-onions by spark discharges in liquid hydrocarbons

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