Large eddy simulation of turbulent flow around a wall mounted hemisphere

Tavakol, Mohammad Mehdi; Abouali, Omid; Yaghoubi, M.

doi:10.1016/j.apm.2014.11.055

Cited by 29 publications

(6 citation statements)

References 23 publications

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“…This corresponds to a Strouhal number of St = 0.16 and is associated with the asymmetric von Kármán shedding process at the lateral sides of the hemisphere. This shedding type was also noticed with a similar Strouhal number in the previously mentioned publications on hemisphere flows (Manhart, 1998;Tavakol et al, 2015;Wood et al, 2016). Furthermore, a Strouhal number of St = 0.40 is found for all displacements.…”

Section: Unsteady Structure Excitationssupporting

confidence: 87%

“…A wide peak is located around 9.5 Hz (Strouhal number St = f D/U ∞ = 0.27) between 8.1 Hz and 10.9 Hz corresponding to a range of Strouhal numbers between 0.24 and 0.32. This peak is connected with the arc-type symmetric vortex shedding process behind the hemisphere described in various publications on hemisphere flows (Manhart, 1998;Tavakol et al, 2015;Wood et al, 2016) and reported to have similar Strouhal numbers. In addition, a major peak at 40 Hz is observed followed by a sudden drop until a second large peak at 102 Hz is observed.…”

Section: Unsteady Structure Excitationssupporting

confidence: 73%

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Experimental studies on the instantaneous fluid–structure interaction of an air-inflated flexible membrane in turbulent flow

Wood

Breuer

Nayer

2018

Journal of Fluids and Structures

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Section: Unsteady Structure Excitationssupporting

confidence: 87%

Section: Unsteady Structure Excitationssupporting

confidence: 73%

Experimental studies on the instantaneous fluid–structure interaction of an air-inflated flexible membrane in turbulent flow

Wood

Breuer

Nayer

2018

Journal of Fluids and Structures

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“…As a result the LES showed excellent agreement with the measurements. An updated comparison between the previous study [27] with the current data revealed the shortcomings of the RNG k-model especially in the wake of the hemisphere. A presentation of time-averaged data focuses on the streamline visualization and surface pressure distribution.…”

Section: Introductionmentioning

confidence: 78%

“…The results showed overall good agreement with the experimental data. Recently, Tavakol et al [27] presented a yet deeper investigation of the hemisphere flow using LES at Re = 3.6 × 10 4 and 6.4 × 10 4 . Based on the earlier study [25] the main focus of this paper was to highlight the superior results of the applied LES compared to the previously performed RANS simulations.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation and Large-Eddy Simulation of the Turbulent Flow past a Smooth and Rigid Hemisphere

Wood

Nayer

Schmidt

et al. 2016

Flow Turbulence Combust

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Computations carried out on the German Federal Top-Level Computer SuperMUC at LRZ Munich under the contract number pr84na.International audienceThe objective of the present paper is to provide a detailed experimental and numerical investigation on the turbulent flow past a hemispherical obstacle (diameter D). For this purpose, the bluff body is exposed to a thick turbulent boundary layer of the thickness δ = D/2 at Re = 50,000. In the experiment this boundary layer thickness is achieved by specific fences placed in the upstream region of the wind tunnel. A detailed measurement of the upstream flow conditions by laser-Doppler and hot-film probes allows to mimic the inflow conditions for the complementary large-eddy simulation of the flow field using a synthetic turbulence inflow generator. These clearly defined boundary and operating conditions are the prerequisites for a combined experimental and numerical investigation of the flow field relying on the laser-Doppler anemometry and a finite-volume Navier-Stokes solver for block-structured curvilinear grids. The results comprise an analysis on the unsteady flow features observed in the vicinity of the hemisphere as well as a detailed discussion of the time-averaged flow field. The latter includes the mean velocity field as well as the Reynolds stresses. Owing to the proper description of the oncoming flow and supplementary numerical studies guaranteeing the choice of an appropriate grid and subgrid-scale model, the results of the measurements and the prediction are found to be in close agreement

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“…Previous studies of airflow around plants have almost exclusively considered trees and grasses (de Langre 2008). 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.…”

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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Large eddy simulation of turbulent flow around a wall mounted hemisphere

Cited by 29 publications

References 23 publications

Experimental studies on the instantaneous fluid–structure interaction of an air-inflated flexible membrane in turbulent flow

Experimental studies on the instantaneous fluid–structure interaction of an air-inflated flexible membrane in turbulent flow

Experimental Investigation and Large-Eddy Simulation of the Turbulent Flow past a Smooth and Rigid Hemisphere

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

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