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Inventions
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New Sights in Fluid Mechanics and Transport Phenomena
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New Sights in Fluid Mechanics and Transport Phenomena

A special issue of Inventions (ISSN 2411-5134). This special issue belongs to the section "Inventions and Innovation in Energy and Thermal/Fluidic Science".

Deadline for manuscript submissions: 30 April 2025 | Viewed by 8510

Special Issue Editor

Prof. Dr. Shyy Woei Chang

E-Mail
Guest Editor
Department of System and Naval Mechatronic Engineering, National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan
Interests: heat transfer enhancement; gas turbine blade cooling; electronic cooling; thermosyphon and heat pipe; heat convection of reciprocating and pulsating flows; cooling of electric motor
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fluid mechanics and transport phenomena are central to the fields of engineering, physics, and chemistry involving thermodynamics, mechanics, and heat and mass transfer. Along with advancements in research methods, new approaches exploring and implementing the fundamental theories of fluid mechanics and transport phenomena for solving engineering problems are constantly being developed. This Special Issue is dedicated to showcasing new findings from theoretical, experimental, and numerical studies of the commonalities between mass, momentum, and heat transport with scientific and engineering applications. The latest advancements in experimental and numerical methods involving fluid mechanics and transport phenomena are also of interest. Potential topics include, but are not limited to, hydrodynamics and aerodynamics, fluid machineries, energy conversion, heat and mass transfer, enhancing heat transfer, future perspectives for transport phenomena, and new experimental and numerical methods in thermal fluids.

Prof. Dr. Shyy Woei Chang
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. Inventions is an international peer-reviewed open access semimonthly 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

  • fluid mechanics
  • fluid machinery
  • heat and mass transfer
  • energy conversion
  • heat transfer enhancement

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Published Papers (5 papers)

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Research

26 pages, 2408 KiB  
Article
Approximate Closed-Form Solution of the Differential Equation Describing Droplet Flight during Sprinkler Irrigation
by Dario Friso
Inventions 2024, 9(4), 73; https://doi.org/10.3390/inventions9040073 - 10 Jul 2024
Viewed by 703
Abstract
Sprinkler irrigation is widely used in agriculture because it allows for rational use of water. However, it can induce negative effects of soil erosion and of surface waterproofing. The scholars of these phenomena use the numerical integration of the equation of motion, but [...] Read more.
Sprinkler irrigation is widely used in agriculture because it allows for rational use of water. However, it can induce negative effects of soil erosion and of surface waterproofing. The scholars of these phenomena use the numerical integration of the equation of motion, but if there was an analytical solution, the study would be facilitated, and this solution could be used as software for regulating sprinklers. Therefore, in this study, the solution of the differential equation of the flight of droplets produced by sprinklers in the absence of wind was developed. The impossibility of an exact analytical solution to the ballistic problem due to the variability of the drag coefficient of the droplets is known; therefore, to find the integrals in closed form, the following were adopted: a new formula for the drag coefficient; a projection of the dynamic’s equation onto two local axes, one tangent and one normal to the trajectory and some linearization. To reduce the errors caused by the latter, the linearization coefficients and their calculation formulas were introduced through multiple non-linear regressions with respect to the jet angle and the initial droplet speed. The analytical modeling obtained, valid for jet angles from 10° to 40°, was compared to the exact numerical solution, showing, for the total travel distance, a high accuracy with a mean relative error MRE of 1.8% ± 1.4%. Even the comparison with the experimental data showed high accuracy with an MRE of 2.5% ±1.1%. These results make the analytical modeling capable of reliably calculating the travel distance, the flight time, the maximum trajectory height, the final fall angle and the ground impact speed. Since the proposed analytical modeling uses only elementary functions, it can be implemented in PLC programmable logic controllers, which could be useful for controlling water waste and erosive effects on the soil during sprinkler irrigation. Full article
(This article belongs to the Special Issue New Sights in Fluid Mechanics and Transport Phenomena)
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24 pages, 8760 KiB  
Article
Satellite Thermal Management Pump Impeller Design and Optimization
by Valeriu Drăgan, Oana Dumitrescu, Cristian Dobromirescu and Ionuț Florian Popa
Inventions 2024, 9(3), 54; https://doi.org/10.3390/inventions9030054 - 6 May 2024
Cited by 1 | Viewed by 1578
Abstract
This study presents a numerical approach to the design and optimization of centrifugal impellers used in the pumps of active thermal control systems of spacecraft. Although launch costs have shrunk in the last decade, the performance requirements, such as efficiency and reliability, have [...] Read more.
This study presents a numerical approach to the design and optimization of centrifugal impellers used in the pumps of active thermal control systems of spacecraft. Although launch costs have shrunk in the last decade, the performance requirements, such as efficiency and reliability, have increased, as such systems are required to work up to 15 years, depending on the mission. To that effect, our paper deals with the first step in this pump design, namely the hydraulic optimization of the impeller. Constructively, this type of impeller allows for certain balancing systems and labyrinth seals to be applied in a more effective way, as well as allowing for additive manufacturing methods to be used—however, details regarding these aspects are beyond the scope of the current paper. By combining empirical formulas, computational fluid dynamics (CFD) analysis, and artificial neural networks (ANNs), the research focuses on achieving high efficiency and fast manufacturing. A series of geometries have been sized and validated using steady-state RANS (Reynolds Averaged Navier-Stokes) simulations, leading to the identification of the most efficient configuration. Subsequent optimization using an ANN resulted in a refined impeller design with notable improvements in hydraulic performance: a 3.55% increase in efficiency and a 7.9% increase in head. Key parameters influencing impeller performance, including blade number, incidence, and backsweep angles, are identified. This approach offers a comprehensive method to address the evolving requirements of space missions and contributes to the advancement of centrifugal pump technology in the space domain. Full article
(This article belongs to the Special Issue New Sights in Fluid Mechanics and Transport Phenomena)
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21 pages, 10382 KiB  
Article
Effects of Perforated Plates on Shock Structure Alteration for NACA0012 Airfoils
by Mihnea Gall, Oana Dumitrescu, Valeriu Drăgan and Daniel Eugeniu Crunțeanu
Inventions 2024, 9(2), 28; https://doi.org/10.3390/inventions9020028 - 5 Mar 2024
Cited by 2 | Viewed by 1684
Abstract
This research investigated a passive flow control technique to mitigate the adverse effects of shock wave–boundary layer interaction on a NACA 0012 airfoil. A perforated plate with a strategically positioned cavity beneath the shock wave anchoring spot was employed. Airfoils with perforated plates [...] Read more.
This research investigated a passive flow control technique to mitigate the adverse effects of shock wave–boundary layer interaction on a NACA 0012 airfoil. A perforated plate with a strategically positioned cavity beneath the shock wave anchoring spot was employed. Airfoils with perforated plates of varying orifice sizes (ranging from 0.5 to 1.2 mm) were constructed using various manufacturing techniques. Experimental analysis utilized an “Eiffel”-type open wind tunnel and a Z-type Schlieren system for flow visualization, along with static pressure measurements obtained from the bottom wall. Empirical observations were compared with steady 3D density-based numerical simulations conducted in Ansys FLUENT for comprehensive analysis and validation. The implementation of the perforated plate induced a significant alteration in shock structure, transforming it from a strong normal shock wave into a large lambda-type shock. The passive control case exhibited a 0.2% improvement in total pressure loss and attributed to the perforated plate’s capability to diminish the intensity of the shock wave anchored above. Significant fluctuations in shear stress were introduced by the perforated plate, with lower stress observed in the plate area due to flow detachment from cavity blowing. Balancing shock and viscous losses proved crucial for achieving a favorable outcome with this passive flow control method. Full article
(This article belongs to the Special Issue New Sights in Fluid Mechanics and Transport Phenomena)
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22 pages, 2378 KiB  
Article
Influence of Density Ratios on Richtmyer–Meshkov Instability with Non-Equilibrium Effects in the Reshock Process
by Tao Yang, Chuandong Lin, Demei Li and Huilin Lai
Inventions 2023, 8(6), 157; https://doi.org/10.3390/inventions8060157 - 13 Dec 2023
Viewed by 1616
Abstract
The Richtmyer–Meshkov instability in a two-component system during the reshock process for various density ratios is studied through the discrete Boltzmann method. Detailed investigations are conducted on both hydrodynamic and thermodynamic non-equilibrium behaviors. Specifically, the analysis focuses on the density gradient, viscous stress [...] Read more.
The Richtmyer–Meshkov instability in a two-component system during the reshock process for various density ratios is studied through the discrete Boltzmann method. Detailed investigations are conducted on both hydrodynamic and thermodynamic non-equilibrium behaviors. Specifically, the analysis focuses on the density gradient, viscous stress tensor, heat flux strength, thermodynamic non-equilibrium intensity, and thermodynamic non-equilibrium area. It is interesting to observe the complex variations to non-equilibrium quantities with the changing shock front, rarefaction wave, transverse wave, and material interface. Physically, the non-equilibrium area is extended as the perturbed material interface grows after the passing of the shock wave or secondary impact. Moreover, the global non-equilibrium manifestation decreases when the transmitted shock front and transverse waves leave or when the reflected rarefaction wave weakens. Additionally, the global thermodynamic non-equilibrium effect is enhanced as the physical gradients or non-equilibrium area increase. Finally, the local non-equilibrium effect decreases when the fluid structure gradually disappears under the action of dissipation/diffusion. Full article
(This article belongs to the Special Issue New Sights in Fluid Mechanics and Transport Phenomena)
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22 pages, 8477 KiB  
Article
Experimental Investigation of a Micro Turbojet Engine Chevrons Nozzle by Means of the Schlieren Technique
by Grigore Cican, Mihnea Gall, Alina Bogoi, Marius Deaconu and Daniel Eugeniu Crunțeanu
Inventions 2023, 8(6), 145; https://doi.org/10.3390/inventions8060145 - 14 Nov 2023
Cited by 2 | Viewed by 2421
Abstract
In connection with subsonic jet noise production, especially regarding the hot jet from a micro turbojet engine, we encountered a lack of recent high-resolution data in the literature describing the flow field using experimental validation through optical diagnoses. The objective of this paper [...] Read more.
In connection with subsonic jet noise production, especially regarding the hot jet from a micro turbojet engine, we encountered a lack of recent high-resolution data in the literature describing the flow field using experimental validation through optical diagnoses. The objective of this paper is to examine and compare the influence on shear layers of the exhaust plug nozzle of a micro turbojet engine with and without chevrons mounted, using a high-speed camera used in Schlieren-type optical system diagnosis. Three different operating regimes are examined for both the baseline configuration and the configuration with 16 triangular-shaped chevrons. In conjunction with the image captures, the sound pressure level was recorded with the help of a microphone placed perpendicular to the flow, 0.4 m from the exhaust of the nozzle which was further processed. In quantitative terms, we found that the OASPL decreases by more than 1% when the engine is operating at higher regimes. Moreover, we found that the average exhaust jet angle, which is a measure of the quality of the fluid mixing layer is increased by 5% with respect to the baseline nozzle. By using the “darkest pixel” technique in Schlieren imaging, we can verify experimentally, for all working regimes, the theory that asserts that subsonic jet noise is a consequence of fine-scale homogeneous turbulence. Additionally, the potential novelty lies in the specific observations related to consistent dispersion of fine-scale eddies and how the presence of chevrons amplifies this uniformity within the turbulent field. Full article
(This article belongs to the Special Issue New Sights in Fluid Mechanics and Transport Phenomena)
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