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Fluids
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Experimental Fluid Mechanics on Bluff Body Wakes and Jets
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Experimental Fluid Mechanics on Bluff Body Wakes and Jets

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: closed (31 March 2024) | Viewed by 10469

Special Issue Editor

Prof. Dr. Tongming Zhou

E-Mail Website
Guest Editor
Department of Civil, Environmental and Mining Engineering, School of Engineering, The University of Western Australia, Crawley, WA 6009, Australia
Interests: fluid mechanics using experimental and numerical methods; wind tunnel testing; large- and small-scale flow structures in vortex-dominated flows; fluid flow control for vortex shedding and mixing manipulation; flow-induced vibration (FIV); energy harvesting from FIV

Special Issue Information

Dear Colleagues,

Experimental fluid mechanics uses state-of-the-art techniques to diagnose flow phenomena and gain a comprehensive understanding of the underlying flow physics in the areas of turbulence, heat transfer, combustion, turbomachinery, biofluids, micro-/nanoscale flows, etc. It has provided scholars with a means of simulating processes to verify novel ideas relevant to fluid dynamics as well as essential ways to validate numerical simulation results. Thus, the advancement, extension and development of fluid mechanics are of vital importance.

Bluff body wakes and jets are widely encountered in many scientific and engineering applications, such as aerospace, coastal, offshore, wind, and environmental engineering, etc. Understanding the features of these flows will enable engineers to produce safer and more cost-effective designs in these areas. The primary aim of this Special Issue is to present current research results in the fields of bluff body wakes and jets, including wake or jet transition, wake or jet interference and the control of wake and jet flows. We welcome original research articles with in-depth discussion as well as review articles summarizing the current state of the research in these areas. The specific topics may include but are not limited to:

  • Wake or jet instability;
  • Vortex formation in wakes and jets;
  • The active and passive control of wakes and jets on vortex shedding and mixing;
  • Wake- or vortex-induced structural vibrations and their control.

Prof. Dr. Tongming Zhou
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

  • jet flow vortices
  • nozzle geometry
  • bluff body wakes
  • vortex shedding
  • flow-induced vibration
  • fluid flow control
  • particle image velocimetry

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Published Papers (4 papers)

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Research

18 pages, 4302 KiB  
Article
Prediction of Geometrical Characteristics of an Inclined Negatively Buoyant Jet Using Group Method of Data Handling (GMDH) Neural Network
by Hassan Alfaifi and Hossein Bonakdari
Fluids 2024, 9(9), 198; https://doi.org/10.3390/fluids9090198 - 28 Aug 2024
Viewed by 735
Abstract
A new approach to predicting the geometrical characteristics of the mixing behavior of an inclined dense jet for angles ranging from 15° to 85° is proposed in this study. This approach is called the group method of data handling (GMDH) and is based [...] Read more.
A new approach to predicting the geometrical characteristics of the mixing behavior of an inclined dense jet for angles ranging from 15° to 85° is proposed in this study. This approach is called the group method of data handling (GMDH) and is based on the artificial neural network (ANN) technique. The proposed model was trained and tested using existing experimental data reported in the literature. The model was then evaluated using statistical indices, as well as being compared with analytical models from previous studies. The results of the coefficient of determination (R2) indicate the high accuracy of the proposed model, with values of 0.9719 and 0.9513 for training and testing for the dimensionless distance from the nozzle to the return point xr/D and 0.9454 and 0.9565 for training and testing for the dimensionless terminal rise height yt/D. Moreover, four previous analytical models were used to evaluate the GMDH model. The results showed the superiority of the proposed model in predicting the geometrical characteristics of the inclined dense jet for all tested angles. Finally, the standard error of the estimate (SEE) was applied to demonstrate which model performed the best in terms of approaching the actual data. The results illustrate that all fitting lines of the GMDH model performed very well for all geometrical parameter predictions and it was the best model, with an approximately 10% error, which was the lowest error value among the models. Therefore, this study confirms that the GMDH model can be used to predict the geometrical properties of the inclined negatively buoyant jet with high performance and accuracy. Full article
(This article belongs to the Special Issue Experimental Fluid Mechanics on Bluff Body Wakes and Jets)
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17 pages, 7238 KiB  
Article
Investigating the Linear Dynamics of the Near-Field of a Turbulent High-Speed Jet Using Dual-Particle Image Velocimetry (PIV) and Dynamic Mode Decomposition (DMD)
by Vishal Chaugule, Alexis Duddridge, Tushar Sikroria, Callum Atkinson and Julio Soria
Fluids 2023, 8(2), 73; https://doi.org/10.3390/fluids8020073 - 17 Feb 2023
Cited by 2 | Viewed by 2570
Abstract
The quest for the physical mechanisms underlying turbulent high-speed jet flows is underpinned by the extraction of spatio-temporal coherent structures from their flow fields. Experimental measurements to enable data decomposition need to comprise time-resolved velocity fields with a high-spatial resolution—qualities which current particle [...] Read more.
The quest for the physical mechanisms underlying turbulent high-speed jet flows is underpinned by the extraction of spatio-temporal coherent structures from their flow fields. Experimental measurements to enable data decomposition need to comprise time-resolved velocity fields with a high-spatial resolution—qualities which current particle image velocimetry hardware are incapable of providing. This paper demonstrates a novel approach that addresses this challenge through the implementation of an experimental high-spatial resolution dual-particle image velocimetry methodology coupled with dynamic mode decomposition. This new approach is exemplified by its application in studying the dynamics of the near-field region of a turbulent high-speed jet, enabling the spatio-temporal structure to be investigated by the identification of the spatial structure of the dominant dynamic modes and their temporal dynamics. The spatial amplification of these modes is compared with that predicted by classical linear stability theory, showing close agreement, which demonstrates the powerful capability of this technique to identify the dominant frequencies and their associated spatial structures in high-speed turbulent flows. Full article
(This article belongs to the Special Issue Experimental Fluid Mechanics on Bluff Body Wakes and Jets)
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19 pages, 13259 KiB  
Article
Suppression of Vortex-Induced Vibration and Phase-Averaged Analysis of the Wake Generated by a Circular Cylinder Covered with Helical Grooves
by Zhiyong Hao, Chenlin Sun, Yucen Lu, Kaiming Bi and Tongming Zhou
Fluids 2022, 7(6), 194; https://doi.org/10.3390/fluids7060194 - 3 Jun 2022
Cited by 11 | Viewed by 3334
Abstract
The effect of triple helical grooves on the suppression of vortex-induced vibration (VIV) of a circular cylinder was investigated experimentally in a wind tunnel over Reynolds number in the range of 1 × 104 < Re < 4 × 104. [...] Read more.
The effect of triple helical grooves on the suppression of vortex-induced vibration (VIV) of a circular cylinder was investigated experimentally in a wind tunnel over Reynolds number in the range of 1 × 104 < Re < 4 × 104. It was found that the helical grooves were effective in suppressing VIV with the peak amplitude reduction of approximately 36%. In addition, the lock-on region was also reduced. To explore the mechanism for the suppression of VIV, experiments on flow structures for a stationary grooved cylinder were also conducted in a wind tunnel at a free stream velocity U∞ of 4.37 m/s, corresponding to a Reynolds number based on the bare cylinder diameter of about 3500. The data were then analyzed using the phase-averaged method to evaluate the coherent vortex structures in the wakes. The results for the stationary grooved cylinder showed that the grooves weakened vortex shedding in the near wake. In addition, the grooves also reduced the drag coefficient by 6.6%. These results help explain the reduction of VIV using helical grooves. Full article
(This article belongs to the Special Issue Experimental Fluid Mechanics on Bluff Body Wakes and Jets)
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18 pages, 7593 KiB  
Article
Turbulent Superstructures in Inert Jets and Diffusion Jet Flames
by Vadim Lemanov, Vladimir Lukashov and Konstantin Sharov
Fluids 2021, 6(12), 459; https://doi.org/10.3390/fluids6120459 - 16 Dec 2021
Cited by 2 | Viewed by 2544
Abstract
An experimental study of spatially localized very large-scale motion superstructures, propagating in a jet of carbon dioxide at low Reynolds numbers, was carried out. A hot-wire anemometer and a high-speed 2D PIV with a frequency of 7 kHz were used as measuring instruments. [...] Read more.
An experimental study of spatially localized very large-scale motion superstructures, propagating in a jet of carbon dioxide at low Reynolds numbers, was carried out. A hot-wire anemometer and a high-speed 2D PIV with a frequency of 7 kHz were used as measuring instruments. Such a puff-type superstructure in a jet with a longitudinal dimension of up to 20–30 nozzle diameters are initially formed in the jet source—a long tube in a laminar-turbulent transition mode (without artificial disturbances). It is shown that this regime with intermittency in time, when part of the time flow is laminar and the other part of time is turbulent, exists both at the exit from the nozzle and in the near field of the jet. Thus, the structural stability of such turbulent superstructures in the near field of the jet was found. Despite the large longitudinal scale, these formations have a transverse dimension of the order of several nozzle diameters. These structures have a complex internal topology, that is, superstructures are a conglomeration of vortices of different sizes from macroscale to microscale. Using the example of diffusion combustion of methane in air, it is demonstrated that in reacting jets, the existence of such large localized perturbations is a powerful physical mechanism for a global change in the flame topology. At the same time, the presence of a cascade of vortices of different sizes in the puff composition can lead to fractal deformation of the flame front. Full article
(This article belongs to the Special Issue Experimental Fluid Mechanics on Bluff Body Wakes and Jets)
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