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Fluids
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Vortex Definition and Identification
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Vortex Definition and Identification

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Turbulence".

Deadline for manuscript submissions: 31 January 2026 | Viewed by 4092

Special Issue Editor

Prof. Dr. Chaoqun Liu

E-Mail Website
Guest Editor
Department of Mathematics, University of Texas at Arlington, Arlington, TX 76019, USA
Interests: vortex; turbulence; DNS/LES; flow transition

Special Issue Information

Dear Colleagues,

Vortices are omnipresent in the universe and affect human life and the environment. A vortex is intuitively recognized as a rotational or swirling fluid motion and develops under diverse conditions. Examples are hurricanes and tornadoes, river and ocean currents, and recirculation and turbulence that develops in pipes and near airplane wings, to mention just a few. Biological organisms, moreover, use the principles behind vortex generation for propulsion and transport. Despite the importance of vortex structures in everyday life, we still do not fully understand vortex generation and its dynamics, and little is known about how to control vortices to avoid their potentially devastating adverse effects. This Special Issue aims to collect a series of papers on vortex definition, identification, and applications including subgrid models for LES, especially using new methods like Liutex and third-generation vortex definition and identification.

Prof. Dr. Chaoqun Liu
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

  • vortex definition
  • identification
  • application
  • turbulence

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Published Papers (3 papers)

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Research

12 pages, 2709 KB  
Article
A Novel Subgrid Model Based on Convection and Liutex
by Yifei Yu and Chaoqun Liu
Fluids 2025, 10(11), 292; https://doi.org/10.3390/fluids10110292 - 11 Nov 2025
Viewed by 167
Abstract
This paper proposes a novel convention-based subgrid scale (SGS) model for large eddy simulation (LES) by using the Liutex concept. Conventional SGS models typically rely on the eddy viscosity assumption, which uses the linear eddy viscosity terms to approximate the nonlinear effects of [...] Read more.
This paper proposes a novel convention-based subgrid scale (SGS) model for large eddy simulation (LES) by using the Liutex concept. Conventional SGS models typically rely on the eddy viscosity assumption, which uses the linear eddy viscosity terms to approximate the nonlinear effects of unresolved turbulent eddies, that should be measured by unresolved Liutex. However, the eddy viscosity assumption is empirical but lacks a scientific foundation, which limits its predictive accuracy. The proposed model in this paper directly models the convective terms and demonstrates several key advantages: (1) the new model gets rid of isotropic assumption for the unresolved SGS eddies which are, in general, anisotropic, (2) the new model contains no empirical coefficients which need to be adjusted case by case, (3) the new model explicitly captures nonlinear convective effects by the SGS eddies and (4) the new model is consistent with the physics for boundary layer as the model becomes zero in the laminar sublayer, where Liutex becomes zero automatically. This new model has been applied in the flat plate boundary transition flow, and the results show that it outperforms the popular and widely adopted wall-adapting local eddy (WALE) model. This new model is a conceptual breakthrough in SGS modeling and has the potential to open a new direction for more accurate SGS models and future LES applications. Full article
(This article belongs to the Special Issue Vortex Definition and Identification)
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19 pages, 18173 KB  
Article
Development of a Lagrangian Temperature Particles Method to Investigate the Flow Around a Rough Bluff Body
by Gabriel Ferraz Marcondes de Carvalho, Tiago Raimundo Chiaradia, Victor Hugo Gava Filho, Paulo Guimarães de Moraes, Alex Mendonça Bimbato and Luiz Antonio Alcântara Pereira
Fluids 2025, 10(11), 288; https://doi.org/10.3390/fluids10110288 - 6 Nov 2025
Viewed by 238
Abstract
This paper presents a roughness surface model for Lagrangian simulations that interacts with both temperature and vorticity fields. The chosen problem is the uniform flow around a rough circular cylinder heated with constant temperature under mixed convection. The methodology used is the Temperature [...] Read more.
This paper presents a roughness surface model for Lagrangian simulations that interacts with both temperature and vorticity fields. The chosen problem is the uniform flow around a rough circular cylinder heated with constant temperature under mixed convection. The methodology used is the Temperature Particles Method (TPM), in which both vorticity and temperature fields are discretized in particles to simulate the real flow in a purely Lagrangian form. The simulation is computationally extensive due to the application of the Biot–Savart law for the two fields and the calculation of buoyancy forces, which is alleviated by the use of parallel programming with OpenMP. The simulation of roughness effects for both fields is obtained using a Large Eddy Simulation (LES) model for vorticity, based on the second-order velocity structure function, which is correlated with the thermal diffusivity through the turbulent Prandtl number. In general, the results indicate that roughness increases the drag coefficient, while an increase in the Richardson number reduces this coefficient. Full article
(This article belongs to the Special Issue Vortex Definition and Identification)
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19 pages, 4608 KB  
Article
Experimental Study on the Influence of Groove-Flap and Concave Cavity on the Output Characteristics of Vertical Axis Wind Turbine
by Jiale Xue, Yongyan Chen, Li Song, Yifan Xing, Baiqiang Wang and Yansong Sun
Fluids 2025, 10(8), 208; https://doi.org/10.3390/fluids10080208 - 8 Aug 2025
Cited by 1 | Viewed by 491
Abstract
To address the low wind energy utilization efficiency of vertical axis wind turbines (VAWTs) and enhance their engineering applicability, cavity and groove-flap structures were incorporated into turbine blades. Numerical simulations were performed to optimize these configurations, followed by wind tunnel experiments investigating output [...] Read more.
To address the low wind energy utilization efficiency of vertical axis wind turbines (VAWTs) and enhance their engineering applicability, cavity and groove-flap structures were incorporated into turbine blades. Numerical simulations were performed to optimize these configurations, followed by wind tunnel experiments investigating output power variations of three VAWT types under different wind speeds at installation angles of 0°, 2°, 4°, and 6°. The Omega criterion was employed to comparatively analyze vortex evolution patterns at the leading and trailing edges for installation angles of 0°, 3°, and 5°. Experimental results demonstrated nonlinear growth in output power with increasing wind speed and rotational velocity, with groove-flap VAWTs exhibiting superior performance. The optimal installation angle was identified within 2.5–3.5°, where appropriate angles reduced adverse pressure gradients, delayed boundary layer separation, and mitigated vortex shedding effects. Excessive angles induced vortex accumulation and wake disturbances, compromising flow field stability. This study provides critical insights for optimizing VAWT aerodynamic performance through structural modifications and installation angle adjustments. Full article
(This article belongs to the Special Issue Vortex Definition and Identification)
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