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Advances and Applications of CFD (Computational Fluid Dynamics)
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Advances and Applications of CFD (Computational Fluid Dynamics)

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Fluid Science and Technology".

Deadline for manuscript submissions: 10 August 2024 | Viewed by 7623

Special Issue Editor

Prof. Dr. Joon Ahn

E-Mail Website
Guest Editor
School of Mechanical Engineering, Kookmin University, 77 Jeongneung-ro, Seongbuk-gu, Seoul 02707, Republic of Korea
Interests: heat transfer; gas turbine; air-conditioning; boiler
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Computational fluid dynamics (CFD) has been applied to various fluid dynamics fields over the past 50 years. In the meantime, great progress has been made in hardware and analysis techniques, and many useful results are emerging in a wider range of applications. In this Special Issue, we would like to collect new techniques of CFD and application cases in various industries and academic fields. It is expected that various advances and applications of CFD, such as phase change, fluid–structure coupling analysis, combustion, and data driven engineering, will be published.

Prof. Dr. Joon Ahn
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. Applied Sciences 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 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 (7 papers)

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Research

25 pages, 6723 KiB  
Article
Effect of Surface Roughness on Aerodynamic Loads of Bluff Body in Vicinity of Smoothed Moving Wall
by Marcos André de Oliveira and Luiz Antonio Alcântara Pereira
Appl. Sci. 2024, 14(7), 2919; https://doi.org/10.3390/app14072919 - 29 Mar 2024
Viewed by 422
Abstract
This paper contributes to a new Lagrangian vortex method for the statistical control of turbulence in two-dimensional flow configurations around a rough circular cylinder in ground effect when considering higher subcritical Reynolds numbers, namely 3 × 104 ≤ Re ≤ 2 × [...] Read more.
This paper contributes to a new Lagrangian vortex method for the statistical control of turbulence in two-dimensional flow configurations around a rough circular cylinder in ground effect when considering higher subcritical Reynolds numbers, namely 3 × 104 ≤ Re ≤ 2 × 105. A smoothed moving wall (active control technique) is used to include the blockage effect in association with the variation in cylinder surface roughness (passive control technique), characterizing a hybrid approach. In contrast with the previous approaches of our research group, the rough cylinder surface is here geometrically constructed, and a new momentum source term is introduced and calculated for the investigated problem. The methodology is structured by coupling the random Discrete Vortex Method, the Lagrangian Dynamic Roughness Model, and the Large Eddy Simulation with turbulence closure using the truncated Second-Order Velocity Structure Function model. This methodological option has the advantage of dispensing with the use of both a refined near-wall mesh and wall functions. The disadvantage of costly processing is readily solved with Open Multi-Processing. The results reveal that intermediate and high roughness values are most efficient for Reynolds numbers on the orders of 105 and 104, respectively. In employing a moving wall, the transition from the large-gap to the intermediate-gap regime is satisfactorily characterized. For the conditions studied with the hybrid technique, it was concluded that the effect of roughness is preponderant and acts to anticipate the characteristics of a lower gap-to-diameter ratio regime, especially with regard to intermittency. Full article
(This article belongs to the Special Issue Advances and Applications of CFD (Computational Fluid Dynamics))
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17 pages, 9925 KiB  
Article
Performance Development of Fluidic Oscillator Nozzle for Cleaning Autonomous-Driving Sensors
by Chan-Hoo Kim, Ji-Hyun Choi and Sung-Young Park
Appl. Sci. 2024, 14(4), 1596; https://doi.org/10.3390/app14041596 - 17 Feb 2024
Viewed by 579
Abstract
Contaminated autonomous-driving sensors frequently malfunction, resulting in accidents; these sensors need regular cleaning. The autonomous-driving sensor-cleaning nozzle currently used is the windshield-washer nozzle; few studies have focused on the sensor-cleaning nozzle. We investigated the flow characteristics of the nozzle to improve its performance [...] Read more.
Contaminated autonomous-driving sensors frequently malfunction, resulting in accidents; these sensors need regular cleaning. The autonomous-driving sensor-cleaning nozzle currently used is the windshield-washer nozzle; few studies have focused on the sensor-cleaning nozzle. We investigated the flow characteristics of the nozzle to improve its performance in cleaning the autonomous-driving sensor. The nozzle concept was based on the fluidic oscillator nozzle. Various performance parameters of the fluidic oscillator nozzle were selected and investigated. Transient fluid flow was simulated to determine the effect of the design parameters to maximize the oscillation flow phenomenon. Additionally, the spray angle and frequency were calculated. Analysis results showed that the change in flow speed affects the frequency, and the change in feedback-channel-inlet flow rate affects the angle change. To verify the simulation result, the three best models (R4+RC10, R6+RC11, R8+RC10) and the base model were manufactured and tested. The test results were consistent with the simulation results within a 6% error. Full article
(This article belongs to the Special Issue Advances and Applications of CFD (Computational Fluid Dynamics))
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17 pages, 5788 KiB  
Article
Direct Numerical Simulation of Turbulent Boundary Layer over Cubical Roughness Elements
by Min Yoon
Appl. Sci. 2024, 14(4), 1418; https://doi.org/10.3390/app14041418 - 08 Feb 2024
Viewed by 481
Abstract
The present study explores turbulence statistics in turbulent flow over urban-like terrain using direct numerical simulation (DNS). DNS is performed in a turbulent boundary layer (TBL) over 3D cubic roughness elements. The turbulence statistics at Reτ = 816 are compared with those [...] Read more.
The present study explores turbulence statistics in turbulent flow over urban-like terrain using direct numerical simulation (DNS). DNS is performed in a turbulent boundary layer (TBL) over 3D cubic roughness elements. The turbulence statistics at Reτ = 816 are compared with those of experimental and numerical studies for validation, where Reτ is the friction Reynolds number. The flow exhibits wake interference characteristics similar to k-type roughness. Logarithmic variations in streamwise and spanwise Reynolds stresses and a plateau in Reynolds shear stress are observed, reminiscent of Townsend’s attached-eddy hypothesis. The energy at long wavelengths near the top of elements extends to smaller scales, indicating a two-scale behavior and a potential link to amplitude modulation. The quadrant analysis of Reynolds shear stress is employed, revealing significant changes in the contributions of ejection and sweep events near the top of elements. The results of quadrant analysis in the outer region closely resemble those of a TBL over a smooth wall, aligning with Townsend’s outer-layer similarity. The analysis of the transport equation of turbulent kinetic energy highlights the role of the roughness elements in energy transfer, especially pressure transport. Streamwise energy is mainly reduced near upstream elements and redirected in other directions. Full article
(This article belongs to the Special Issue Advances and Applications of CFD (Computational Fluid Dynamics))
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24 pages, 10110 KiB  
Article
Numerical Study of Aircraft Wake Vortex Evolution under the Influence of Vertical Winds
by Jianhui Yuan, Jixin Liu, Changcheng Li and Zheng Zhao
Appl. Sci. 2024, 14(1), 86; https://doi.org/10.3390/app14010086 - 21 Dec 2023
Viewed by 683
Abstract
Separating wake vortices is crucial for aircraft landing safety and essential to airport operational efficiency. Vertical wind, as a typical atmospheric condition, plays a significant role, and studying the evolution characteristics of wake vortices under this condition is of paramount importance for developing [...] Read more.
Separating wake vortices is crucial for aircraft landing safety and essential to airport operational efficiency. Vertical wind, as a typical atmospheric condition, plays a significant role, and studying the evolution characteristics of wake vortices under this condition is of paramount importance for developing dynamic wake separation systems. In this study, we employed the SST k-ω turbulence model based on an O-Block structured grid to numerically simulate the simplified wing model. We analyzed the variations in the wake vortex structure and parameters of the Airbus A320 during the near-field phase under different vertical wind directions and speeds. The results indicate that favorable vertical winds cause a “flattening” deformation in the wake vortex. Vertical winds reduce the initial vortex strength, accelerate the rate of vortex decay, and influence the trajectory of the vortex core. Notably, under wind speeds of 1~3 m/s, the decay rate is more significant than under 4 m/s. When vertical wind speeds are substantial, it can lead to irregular motion and interactions within the vortex core, forming secondary vortices. Full article
(This article belongs to the Special Issue Advances and Applications of CFD (Computational Fluid Dynamics))
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17 pages, 9491 KiB  
Article
Comparison of Mixing Plane, Frozen Rotor, and Sliding Mesh Methods on a Counter-Rotating Dual-Rotor Wind Turbine
by Ferenc Szlivka, Csaba Hetyei, Gusztáv Fekete and Ildikó Molnár
Appl. Sci. 2023, 13(15), 8982; https://doi.org/10.3390/app13158982 - 05 Aug 2023
Viewed by 1815
Abstract
Nowadays, there are numerous new features available in CFD (computational fluid dynamics) that can simulate complex physical phenomena, which used to be challenging to address. However, in current CFD software, certain problems can be simulated using different approaches. In our article, we chose [...] Read more.
Nowadays, there are numerous new features available in CFD (computational fluid dynamics) that can simulate complex physical phenomena, which used to be challenging to address. However, in current CFD software, certain problems can be simulated using different approaches. In our article, we chose different rotating motion methods to analyze a counter-rotating dual-rotor wind turbine (CO-DRWT). Using the different rotating motion approaches we selected (mixing plane, frozen rotor, and sliding mesh), we examined the torque on the rotors and compared them. The following conclusion was reached. If transient fluid flow must be examined, then the sliding mesh method provided the most realistic results, while the frozen rotor method was adequate if we investigated the effect of wake and vortex near the rotating blades or on its environment. The mixing plane method should be used when the focus is on the kinetics and kinematics of the rotating blade or structure. Full article
(This article belongs to the Special Issue Advances and Applications of CFD (Computational Fluid Dynamics))
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16 pages, 8050 KiB  
Article
Dispersion Simulations of Exhaust Smoke Discharged from Anchor-Handling Tug Supply Vessel under Various Wind Conditions
by Se-Min Jeong, Hae Jin Ji, Kwang-Leol Jeong and Sunho Park
Appl. Sci. 2023, 13(13), 7752; https://doi.org/10.3390/app13137752 - 30 Jun 2023
Viewed by 845
Abstract
Exhaust smoke discharged from marine vessels and offshore plants not only contaminates the hull and cargo but is also the main cause of deterioration in the crew’s health and working environment. Rules and regulations have been implemented and have become stricter in recent [...] Read more.
Exhaust smoke discharged from marine vessels and offshore plants not only contaminates the hull and cargo but is also the main cause of deterioration in the crew’s health and working environment. Rules and regulations have been implemented and have become stricter in recent decades. In this study, the exhaust smoke flow around an anchor-handling tug supply vessel in a stationary state, which has been seldom studied, is analyzed using computational fluid dynamics. The study investigates the effect of changing the wind speed and direction, which primarily affects the flow and dispersion of the smoke, to verify the suitability of the environment for the crew. To assess the environment, the recommended and comfortable concentrations of NO2 are used. The results demonstrate that a higher wind speed worsens the effect of the exhaust flow on the environment, owing to lower-pressure values and regions behind the structures. The emission of exhaust smoke is unsatisfactory when the wind flows from the side or rear of the vessel, instead of from the bow. Differing from previous studies conducted on general merchant vessels in navigating conditions, it was found that side winds can also have detrimental environmental effects in the stationary state. Adopting the original design of exhaust pipes leads to the distribution of exhaust smoke over the deck, exceeding the recommended exposure limit. Increasing the height of the pipes is identified as a simple but effective method to facilitate the smooth discharge of exhaust smoke. Full article
(This article belongs to the Special Issue Advances and Applications of CFD (Computational Fluid Dynamics))
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16 pages, 9305 KiB  
Article
Effect of Impeller Trimming on the Energy Efficiency of the Counter-Rotating Pumping Stage
by Ivan Pavlenko, Oleksandr Kulikov, Oleksandr Ratushnyi, Vitalii Ivanov, Ján Piteľ and Vladyslav Kondus
Appl. Sci. 2023, 13(2), 761; https://doi.org/10.3390/app13020761 - 05 Jan 2023
Cited by 6 | Viewed by 1533
Abstract
Developing ways to increase centrifugal pumps’ pressure and power characteristics is a critical problem in up-to-date engineering. There are many ways to resolve it, but each has advantages and flaws. The presented article aimed to ensure higher energy efficiency indicators by using a [...] Read more.
Developing ways to increase centrifugal pumps’ pressure and power characteristics is a critical problem in up-to-date engineering. There are many ways to resolve it, but each has advantages and flaws. The presented article aimed to ensure higher energy efficiency indicators by using a counter-rotating pumping stage with trimming. During the research, the comprehensive approach was based on CFD modeling and the Moore–Penrose pseudoinverse approach for overestimated systems. According to the obtained data, pumps with a counter-rotating stage allowed the pressure head to be significantly increased compared with the standard design of the flow part. Notably, for pumping units CPS 180/1900 with a basic stage, the pressure head of 127 m was reached. However, when using a counter-rotating stage, the pressure head could be increased up to 270 m, which was 2.1 times higher. Therefore, to ensure unchanged characteristics when using centrifugal pumps with the counter-rotating stage, the weight and size indicators can be significantly reduced compared to the traditional design scheme. The proposed numerical and analytical approaches allow estimating the highest pressure and energy characteristics values. Full article
(This article belongs to the Special Issue Advances and Applications of CFD (Computational Fluid Dynamics))
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