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Fluids
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Scientific Computing in Fluids
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Scientific Computing in Fluids

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Mathematical and Computational Fluid Mechanics".

Deadline for manuscript submissions: closed (15 November 2021)

Special Issue Editor

Dr. Michel Bergmann

E-Mail Website
Guest Editor
Memphis Team, Inria Bordeaux - Sud-Ouest, F-33400 Talence, France
Interests: computational fluid mechanics; numerical methods; scientific computing and parallel computing; reduced order models; fluid-structure interactions; bio-inspired locomotion

Special Issue Information

Dear Colleagues,

The nature of fluid flow encountered in biological, medical, or industrial processes is significantly different, and it can range from very sluggish to very high-speed flows. Moreover, in most of these applications, fluid-structure interaction is also a dominant phenomenon.  Consequently, various mathematical and numerical techniques are constantly being pursued in the literature to solve these complex flow problems efficiently on large-scale computing platforms. While higher solution accuracy is always desired, many real-time industrial applications cannot afford the overhead of large compute time associated with high-fidelity methods. This is also motivating researchers to develop reduced-order models, that are accurate enough to make real-time decisions for large industrial-scale problems.

The aim of this Special Issue is to provide an overview of the most recent developments in the Scientific Computing field to effectively tackle such complex flow and fluid-structure interaction problems. In a non-exhaustive way, this Special Issue aims to present new ideas and algorithms in both low and high dimensions that can be used to address challenging real-world applications.

Dr. Michel Bergmann
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • scientific computation
  • mathematical modeling
  • numerical analysis and simulations
  • reduced-order models
  • high performance computing
  • fluid-structure interacting
  • machine learning
  • real-time and adaptive control

Published Papers (5 papers)

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Research

21 pages, 9907 KiB  
Article
Computational Analysis of Actuation Techniques Impact on the Flow Control around the Ahmed Body
by Stephie Edwige, Philippe Gilotte and Iraj Mortazavi
Fluids 2022, 7(2), 52; https://doi.org/10.3390/fluids7020052 - 24 Jan 2022
Cited by 2 | Viewed by 2124
Abstract
Active flow control with jet devices is a promising approach for vehicle aerodynamics control. In this work an extended computational study is performed comparing three different actuation strategies for active flow control around the square back Ahmed body at Reynolds number 500,000 (based [...] Read more.
Active flow control with jet devices is a promising approach for vehicle aerodynamics control. In this work an extended computational study is performed comparing three different actuation strategies for active flow control around the square back Ahmed body at Reynolds number 500,000 (based on the vehicle height). Numerical simulations are run using a Large Eddy Simulation (LES) approach, well adapted to calculate the unsteady high Reynolds number flow control using periodic jet devices. computations are validated comparing to in-house experiments for uncontrolled and some controlled cases. The novelty of this investigation is mainly related to the in-depth study of the base flow and actuation approaches by an accurate LES method and their comparison to experiments. Here, several simulations are performed to estimate the effect of active controls on the flow topology and the drag reduction. Beside the continuous blowing jet, three periodic actuation techniques including periodic blowing and suction as well as the zero flux synthetic jet devices are explored. The slots are implemented discontinuously in order to achieve a better control efficiency linked to vortex generation. In this framework, spectral analyses on global aerodynamical quantities, rear pressure/drag coefficient behavior examination as well as wake structure investigations are performed in order to compare these jet actuations. As a result, shear layer variations are observed during the blowing phase, but the main flow topology change occurs with suction and synthetic jets. Rear back pressure is therefore substantially increased. Full article
(This article belongs to the Special Issue Scientific Computing in Fluids)
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24 pages, 1295 KiB  
Article
A Cartesian Method with Second-Order Pressure Resolution for Incompressible Flows with Large Density Ratios
by Michel Bergmann and Lisl Weynans
Fluids 2021, 6(11), 402; https://doi.org/10.3390/fluids6110402 - 6 Nov 2021
Cited by 1 | Viewed by 1486
Abstract
An Eulerian method to numerically solve incompressible bifluid problems with high density ratio is presented. This method can be considered as an improvement of the Ghost Fluid method, with the specificity of a sharp second-order numerical scheme for the spatial resolution of the [...] Read more.
An Eulerian method to numerically solve incompressible bifluid problems with high density ratio is presented. This method can be considered as an improvement of the Ghost Fluid method, with the specificity of a sharp second-order numerical scheme for the spatial resolution of the discontinuous elliptic problem for the pressure. The Navier–Stokes equations are integrated in time with a fractional step method based on the Chorin scheme and discretized in space on a Cartesian mesh. The bifluid interface is implicitly represented using a level-set function. The advantage of this method is its simplicity to implement in a standard monofluid Navier–Stokes solver while being more accurate and conservative than other simple classical bifluid methods. The numerical tests highlight the improvements obtained with this sharp method compared to the reference standard first-order methods. Full article
(This article belongs to the Special Issue Scientific Computing in Fluids)
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17 pages, 962 KiB  
Article
Scaling, Complexity, and Design Aspects in Computational Fluid Dynamics
by Sheldon Wang
Fluids 2021, 6(10), 362; https://doi.org/10.3390/fluids6100362 - 12 Oct 2021
Cited by 2 | Viewed by 1485
Abstract
With the availability of more and more efficient and sophisticated Computational Fluid Dynamics (CFD) tools, engineering designs are also becoming more and more software driven. Yet, the insights in temporal and spatial scaling issues are still with us and very often imbedded in [...] Read more.
With the availability of more and more efficient and sophisticated Computational Fluid Dynamics (CFD) tools, engineering designs are also becoming more and more software driven. Yet, the insights in temporal and spatial scaling issues are still with us and very often imbedded in complexity and many design aspects. In this paper, with a revisit to a so-called leakage issue in sucker rod pumps prevalent in petroleum industries, the author would like to demonstrate the need to use perturbation approaches to circumvent the multi-scale challenges in CFD with extreme spatial aspect ratios and temporal scales. In this study, the gap size between the outer surface of the plunger and the inner surface of the barrel is measured with a mill (one thousandth of an inch) whereas the plunger axial length is measured with inches or even feet. The temporal scales, namely relaxation times, are estimated with both expansions in Bessel functions for the annulus flow region and expansions in Fourier series when such a narrow circular flow region is approximated with a rectangular one. These engineering insights derived from the perturbation approaches have been confirmed with the use of full-fledged CFD analyses with sophisticated computational tools as well as experimental measurements. With these confirmations, new perturbation studies on the sucker rod leakage issue with eccentricities have been presented. The volume flow rate or rather leakage due to the pressure difference is calculated as a quadratic function with respect to the eccentricity, which matches with the early prediction and publication with comprehensive CFD studies. In short, a healthy combination of ever more powerful modeling tools along with the physics, mathematics, and engineering insights with dimensionless numbers and classical perturbation approaches may provide a balanced and more flexible and efficient strategy in complex engineering designs with the consideration of parametric and phase spaces. Full article
(This article belongs to the Special Issue Scientific Computing in Fluids)
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22 pages, 6873 KiB  
Article
Towards Reconstruction of Complex Flow Fields Using Unit Flows
by Paul J. Kristo, Mark L. Kimber and Sharath S. Girimaji
Fluids 2021, 6(7), 255; https://doi.org/10.3390/fluids6070255 - 13 Jul 2021
Cited by 2 | Viewed by 1901
Abstract
Many complex turbulent flows in nature and engineering can be qualitatively regarded as being constituted of multiple simpler unit flows. The objective of this work is to characterize the coherent structures in such complex flows as a combination of constituent unitary flow structures [...] Read more.
Many complex turbulent flows in nature and engineering can be qualitatively regarded as being constituted of multiple simpler unit flows. The objective of this work is to characterize the coherent structures in such complex flows as a combination of constituent unitary flow structures for the purpose of reduced-order representation. While turbulence is clearly a non-linear phenomenon, we aim to establish the degree to which the optimally weighted superposition of unitary flow structures can represent the complex flow structures. The rationale for investigating such superposition stems from the fact that the large-scale coherent structures are generated by underlying flow instabilities that may be reasonably described using linear analysis. Clearly, the degree of validity of superposition will depend on the flow under consideration. In this work, we take the first step toward establishing a procedure for investigating superposition. Experimental data of single and triple tandem jets in crossflow are used to demonstrate the procedure. A composite triple tandem jet flow field is generated from optimal superposition of single jet data and compared against ‘true’ triple jet data. Direct comparisons between the true and composite fields are made for spatial, temporal, and kinetic energy content. The large-scale features (obtained from proper orthogonal decomposition or POD) of true and composite tandem jet wakes exhibit nearly 70% agreement in terms of modal eigenvector correlation. Corresponding eigenvalues reveal that the kinetic energy of the flow is also emulated with only a slight overprediction. Temporal frequency features are also examined in an effort to completely characterize POD modes. The proposed method serves as a foundation for more rigorous and robust dimensional reduction in complex flows based on unit flow modes. Full article
(This article belongs to the Special Issue Scientific Computing in Fluids)
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22 pages, 44140 KiB  
Article
Investigation of the Tribological Performance of Heterogeneous Slip/No-Slip Journal Bearing Considering Thermo-Hydrodynamic Effects
by Mohammad Tauviqirrahman, M. Fadhli Afif, P. Paryanto, J. Jamari and Wahyu Caesarendra
Fluids 2021, 6(2), 48; https://doi.org/10.3390/fluids6020048 - 21 Jan 2021
Cited by 15 | Viewed by 3139
Abstract
The slip boundary has an important influence on hydrodynamic journal bearing. However, less attention has been paid to the positive effect of slip on thermal behaviour. In this study, a computational fluid dynamics (CFD) analysis investigating the thermo-hydrodynamic (THD) characteristics of heterogeneous slip/no-slip [...] Read more.
The slip boundary has an important influence on hydrodynamic journal bearing. However, less attention has been paid to the positive effect of slip on thermal behaviour. In this study, a computational fluid dynamics (CFD) analysis investigating the thermo-hydrodynamic (THD) characteristics of heterogeneous slip/no-slip bearings running under steady, incompressible, and turbulent conditions is presented. A comprehensive analysis is made to investigate the THD behaviours of heterogeneous slip/no-slip bearings in terms of lubricant pressure, temperature distribution, volume fraction of vapor, and load-carrying capacity when they are running under different shaft rotational speeds. The multiphase cavitation model is adopted to represent the real operational condition of the journal bearing. Numerical results show that the load-carrying capacity of the heterogeneous slip/no-slip bearing can be significantly increased by up to 100% depending on the rotational speed. It is also observed that there is an optimal journal rotational speed for maximizing the load-carrying capacity. An insightful new finding is revealed in a numerical framework, wherein it is found that by introducing the heterogeneous slip/no-slip pattern, the maximum temperature can be reduced by up to 25% in comparison with a conventional bearing. Full article
(This article belongs to the Special Issue Scientific Computing in Fluids)
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