Smart Transparency for Illustrative Visualization of Complex Flow Surfaces

This section of the book revisits a question from the book The Lattice Boltzmann Equation (for fluid dynamics and beyond). This question is: What did we learn through lattice Boltzmann? Did LB make a real difference to our understanding of the physics of fluids and flowing matter in general? Here, the text aims to offer a subjective view, without the presumption of being right. Besides being routinely used for a broad spectrum of complex flow problems, there are, in the opinion expressed in this part of the book, a few precious instances in which LB has made a palpable difference.

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Modeling the Turbulent Wake Behind a Wall-Mounted Square Cylinder

Logic Journal of IGPL ◽

10.1093/jigpal/jzaa060 ◽

2020 ◽

Author(s):

Christian Amor ◽

José M Pérez ◽

Philipp Schlatter ◽

Ricardo Vinuesa ◽

Soledad Le Clainche

Keyword(s):

Proper Orthogonal Decomposition ◽

Turbulent Wake ◽

Orthogonal Decomposition ◽

Dynamic Mode Decomposition ◽

Dynamic Mode ◽

Square Cylinder ◽

Complex Flow ◽

Reduced Order ◽

Mode Decomposition ◽

Proper Orthogonal

Abstract This article introduces some soft computing methods generally used for data analysis and flow pattern detection in fluid dynamics. These techniques decompose the original flow field as an expansion of modes, which can be either orthogonal in time (variants of dynamic mode decomposition), or in space (variants of proper orthogonal decomposition) or in time and space (spectral proper orthogonal decomposition), or they can simply be selected using some sophisticated statistical techniques (empirical mode decomposition). The performance of these methods is tested in the turbulent wake of a wall-mounted square cylinder. This highly complex flow is suitable to show the ability of the aforementioned methods to reduce the degrees of freedom of the original data by only retaining the large scales in the flow. The main result is a reduced-order model of the original flow case, based on a low number of modes. A deep discussion is carried out about how to choose the most computationally efficient method to obtain suitable reduced-order models of the flow. The techniques introduced in this article are data-driven methods that could be applied to model any type of non-linear dynamical system, including numerical and experimental databases.

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Low-cost Solutions for Velocimetry in Rotating and Opaque Fluid Experiments using Ultrasonic Time of Flight

Experimental Techniques ◽

10.1007/s40799-021-00469-x ◽

2021 ◽

Author(s):

Fabian Burmann ◽

Jerome Noir ◽

Stefan Beetschen ◽

Andrew Jackson

Keyword(s):

Acoustic Waves ◽

Flow Measurement ◽

Low Cost ◽

Time Of Flight ◽

Zonal Flow ◽

Gravitational Acceleration ◽

Complex Flow ◽

Ultrasonic Time ◽

Theoretical Predictions ◽

Complex Flow Structure

AbstractMany common techniques for flow measurement, such as Particle Image Velocimetry (PIV) or Ultrasonic Doppler Velocimetry (UDV), rely on the presence of reflectors in the fluid. These methods fail to operate when e.g centrifugal or gravitational acceleration leads to a rarefaction of scatterers in the fluid, as for instance in rapidly rotating experiments. In this article we present two low-cost implementations for flow measurement based on the transit time (or Time of Flight) of acoustic waves, that do not require the presence of scatterers in the fluid. We compare our two implementations against UDV in a well controlled experiment with a simple oscillating flow and show we can achieve measurements in the sub-centimeter per second velocity range with an accuracy of $\sim 5-10\%$ ∼ 5 − 10 % . We also perform measurements in a rotating experiment with a complex flow structure from which we extract the mean zonal flow, which is in good agreement with theoretical predictions.

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Estimation of characteristic vortex structures in complex flow

Journal of Turbulence ◽

10.1080/14685248.2021.1932939 ◽

2021 ◽

pp. 1-18

Author(s):

Kaustav Chaudhury ◽

Chandranath Banerjee ◽

Swapnil Urankar

Keyword(s):

Vortex Structures ◽

Complex Flow

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Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

Applied Sciences ◽

10.3390/app11157167 ◽

2021 ◽

Vol 11 (15) ◽

pp. 7167

Author(s):

Liang Xu ◽

Xu Zhao ◽

Lei Xi ◽

Yonghao Ma ◽

Jianmin Gao ◽

...

Keyword(s):

Heat Transfer ◽

Large Eddy Simulation ◽

Wall Temperature ◽

Target Surface ◽

Impinging Jets ◽

Small Scale ◽

Complex Flow ◽

Eddy Simulation ◽

Flow And Heat Transfer ◽

Large Eddy

Swirling impinging jet (SIJ) is considered as an effective means to achieve uniform cooling at high heat transfer rates, and the complex flow structure and its mechanism of enhancing heat transfer have attracted much attention in recent years. The large eddy simulation (LES) technique is employed to analyze the flow fields of swirling and non-swirling impinging jet emanating from a hole with four spiral and straight grooves, respectively, at a relatively high Reynolds number (Re) of 16,000 and a small jet spacing of H/D = 2 on a concave surface with uniform heat flux. Firstly, this work analyzes two different sub-grid stress models, and LES with the wall-adapting local eddy-viscosity model (WALEM) is established for accurately predicting flow and heat transfer performance of SIJ on a flat surface. The complex flow field structures, spectral characteristics, time-averaged flow characteristics and heat transfer on the target surface for the swirling and non-swirling impinging jets are compared in detail using the established method. The results show that small-scale recirculation vortices near the wall change the nearby flow into an unstable microwave state, resulting in small-scale fluctuation of the local Nusselt number (Nu) of the wall. There is a stable recirculation vortex at the stagnation point of the target surface, and the axial and radial fluctuating speeds are consistent with the fluctuating wall temperature. With the increase in the radial radius away from the stagnation point, the main frequency of the fluctuation of wall temperature coincides with the main frequency of the fluctuation of radial fluctuating velocity at x/D = 0.5. Compared with 0° straight hole, 45° spiral hole has a larger fluctuating speed because of speed deflection, resulting in a larger turbulence intensity and a stronger air transport capacity. The heat transfer intensity of the 45° spiral hole on the target surface is slightly improved within 5–10%.

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Mineralogy, Geochemistry and Provenance of Coastal Sands from Greece: New Insights on the REE Content of Black Coastal Sands from Aggelochori Area, N.-Greece

Minerals ◽

10.3390/min11070693 ◽

2021 ◽

Vol 11 (7) ◽

pp. 693

Author(s):

Argyrios Papadopoulos ◽

Stylianos Lazaridis ◽

Afroditi Kipourou-Panagiotou ◽

Nikolaos Kantiranis ◽

Antonios Koroneos ◽

...

Keyword(s):

Major And Trace Elements ◽

Heavy Minerals ◽

Sea Waves ◽

Complex Flow ◽

Fine Grained ◽

Microscopy Analysis ◽

Beach Sands ◽

Geochemical Analyses ◽

The One ◽

Black Color

Beach sands from Aggelochori coast line are investigated for their geochemistry and REE content, mineralogy and their provenance. These fluvial sands bear heavy minerals enriched horizons (containing minerals such as magnetite, zircon, ilmenite, hematite, rutile and titanite) that can be distinguished due to their black color and are formed usually due to the action of sea waves that deposit the heavy minerals and remove the lighter ones. After a suitable processing (washing, sieving, drying and magnetic separation) of the samples, the mineral constituents and their presence (wt.%) were estimated by XRD. Among the samples, the one being simultaneously the more fine grained and the more zircon-enriched (as suggested by XRPD data and optical microscopy analysis) has been selected for further geochemical analyses. The major and trace elements contents were compared to previously studied REE enriched beach sands from Kavala and Sithonia. Beach sands from Aggelochori area appear to have relatively low REE contents. Considering the provenance of these sediments, we suggest that these sands, are a product of the erosion of multi-sources, including the near-by Monopigado granite, as well as metamorphic rocks, as indicated by the presence of rutile and both ilmenite and magnetite in some samples. Therefore, there are indications of a complex flow pattern that existed at the paleo-catchment area of the deposition.

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