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Symmetry
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Applications Based on Symmetry/Asymmetry in Fluid Mechanics
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Applications Based on Symmetry/Asymmetry in Fluid Mechanics

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Engineering and Materials".

Deadline for manuscript submissions: 31 May 2024 | Viewed by 2351

Special Issue Editor

Prof. Dr. Xi Chen

E-Mail Website
Guest Editor
Institute of Fluids, Beihang University, Beijing, China
Interests: turbulence theory; flow drag reduction; turbulence modeling; vortex dynamics

Special Issue Information

Dear Colleagues,

Symmetry is found everywhere, including many fluid processes. This symmetry can be either on the space–time level or on the time level. The applications of symmetry in fluid mechanics are usually interdisciplinary, such as mechanical, aerospace, chemical, and process engineering. Therefore, their exploration is crucial for many real-life applications. This Special Issue focuses on the following topics, but is not limited to them: the importance of symmetry in a variety of fluid flows, heat transfer and its applications, including heat exchangers, thermal storage, heat pipes, etc.

We welcome submissions from researchers regarding advances in fluid mechanics, as well as from researchers exploring interdisciplinary linkages between fluid mechanics and other fields and beyond.

Prof. Dr. Xi Chen
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. Symmetry 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 2400 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.

Published Papers (3 papers)

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Research

20 pages, 18983 KiB  
Article
A Lagrangian Analysis of Tip Leakage Vortex in a Low-Speed Axial Compressor Rotor
by Jiexuan Hou, Yangwei Liu and Yumeng Tang
Symmetry 2024, 16(3), 344; https://doi.org/10.3390/sym16030344 - 13 Mar 2024
Viewed by 631
Abstract
A Lagrangian method is introduced to analyze the tip leakage vortex (TLV) behavior in a low-speed axial compressor rotor. The finite-time Lyapunov exponent (FTLE) fields are calculated based on the delayed detached-eddy simulation (DDES) results and identifying the FTLE ridges as Lagrangian coherent [...] Read more.
A Lagrangian method is introduced to analyze the tip leakage vortex (TLV) behavior in a low-speed axial compressor rotor. The finite-time Lyapunov exponent (FTLE) fields are calculated based on the delayed detached-eddy simulation (DDES) results and identifying the FTLE ridges as Lagrangian coherent structures (LCSs). The computational method of the FTLE field in three-dimensional unsteady flow fields is discussed and then applied to the instantaneous flow fields at both the design and near-stall conditions. Results show that the accuracy of the particle trajectory and the density of the initial grid of the particle trajectory greatly affect the results of the FTLE field and, thus, the LCSs. Compared to the Eulerian Q method, which is calculated based on the symmetric and anti-symmetric components of the local velocity gradient tensor, the Lagrangian method has great potential in unraveling the mechanism of complex vortex structures. The LCSs show a transport barrier between the TLV and the secondary TLV, indicating two separate vortices. The aLCSs show the bubble-like and bar-like structure in the isosurfaces corresponding to the bubble and spiral breakdown patterns. Full article
(This article belongs to the Special Issue Applications Based on Symmetry/Asymmetry in Fluid Mechanics)
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12 pages, 505 KiB  
Article
Low-Order Moments of Velocity Gradient Tensors in Two-Dimensional Isotropic Turbulence
by Chensheng Luo, Ping-Fan Yang and Le Fang
Symmetry 2024, 16(2), 175; https://doi.org/10.3390/sym16020175 - 01 Feb 2024
Viewed by 567
Abstract
In isotropic turbulence, symmetry of different directions can reduce the number of independent components for velocity gradient tensors. In three-dimensional isotropic turbulence, the independent components under either incompressible or compressible conditions have already been analyzed in the literature. However, for two-dimensional isotropic turbulence, [...] Read more.
In isotropic turbulence, symmetry of different directions can reduce the number of independent components for velocity gradient tensors. In three-dimensional isotropic turbulence, the independent components under either incompressible or compressible conditions have already been analyzed in the literature. However, for two-dimensional isotropic turbulence, they are still unclear. We derive rigorously the independent components for velocity gradient tensors of two-dimensional isotropic turbulence and give physical explanations. These theoretical results are validated using high-resolution direct numerical simulations (DNSs) of two-dimensional compressible turbulence. Results show that the present DNS setup is still not sufficient to capture the isotropy of third-order moments, suggesting that more investigations on determining the smallest scale and improving the numerical schemes for two-dimensional compressible turbulence are required. Full article
(This article belongs to the Special Issue Applications Based on Symmetry/Asymmetry in Fluid Mechanics)
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13 pages, 3998 KiB  
Article
Symmetry Analysis of Mean Velocity Distribution in Stratified Atmospheric Surface Layers
by Yong Ji and Xi Chen
Symmetry 2023, 15(10), 1951; https://doi.org/10.3390/sym15101951 - 21 Oct 2023
Viewed by 673
Abstract
The mean velocity distributions of unstably and stably stratified atmospheric surface layers (ASLs) are investigated here using the symmetry approach. Symmetry groups for the mean momentum and the Reynolds stress equations of ASL are searched under random dilation transformations, which, with different leading [...] Read more.
The mean velocity distributions of unstably and stably stratified atmospheric surface layers (ASLs) are investigated here using the symmetry approach. Symmetry groups for the mean momentum and the Reynolds stress equations of ASL are searched under random dilation transformations, which, with different leading order balances in different flow regions, lead to a set of specific scalings for the characteristic length ℓ13 (defined by Reynolds shear stress and mean shear). In particular, symmetry analysis shows that in the shear-dominated region, ℓ13 scales linearly with the surface height z, which corresponds to the classical log law of mean velocity. In the buoyancy-dominated region, ℓ13/L∼z/L4/3 for unstably stratified ASL and ℓ13/L∼const for stably stratified ASL, where L is the Obukhov length. The specific formula of the celebrated Monin–Obukhov similarity function is obtained, and hence an algebraic model of mean velocity profiles in ASL is derived, showing good agreement with the datum from the QingTu Lake observation array (QLOA) in China. Full article
(This article belongs to the Special Issue Applications Based on Symmetry/Asymmetry in Fluid Mechanics)
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