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Computational Fluid Dynamics for Future Energies
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Computational Fluid Dynamics for Future Energies

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Mechanical Engineering".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 14364

Special Issue Editor

Prof. Dr. Jae-Ho Jeong

E-Mail Website
Guest Editor
Department of Mechanical Engineering, Gachon University, Seongnam, Gyeonggi 461-701, Republic of Korea
Interests: modification of polymers through cross-linking, grafting, degradation, etc., via chemical or radiation methods and applications; improvement of physical–chemical properties of hydrogels for medical applications
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Thanks to rapid development and expansion of computational resources and numerical techniques in the past 30 years, we have been able to extend the depth of our understanding on thermal and fluid engineering for future energies through computational fluid dynamics simulation.

 In particular, research exploring the numerical elucidation for understanding unsteady nature and microscopic analysis has been spotlighted in the field of thermal and fluid engineering. Through modeling and simulation based on Navier-Stokes Equation, we can deeply grasp the details of the heat transfer characteristics and the vortical flow structure behavior that make up physical performances for thermal and fluid energy machines in the future.

The main goal of this Special Issue is to collect the latest contributions to research topics on thermal and fluid engineering for future energies. We welcome all kinds of computational/theoretical approaches. Furthermore, multi-scale modeling that combines two or more simulation methodologies, coupling computer simulation with experiments or structural analysis, and new design concept for energy system, and design optimization through machine learning algorithms are also highly recommended.

Prof. Dr. Jae-Ho Jeong
Guest Editor

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Keywords

  • computational fluid dynamics
  • renewable energy, fluid machinery
  • thermal-hydraulics
  • nuclear energy

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Published Papers (5 papers)

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Research

10 pages, 1762 KiB  
Communication
Pix2Pix and Deep Neural Network-Based Deep Learning Technology for Predicting Vortical Flow Fields and Aerodynamic Performance of Airfoils
by Han-Seop Song, Jophous Mugabi and Jae-Ho Jeong
Appl. Sci. 2023, 13(2), 1019; https://doi.org/10.3390/app13021019 - 11 Jan 2023
Cited by 6 | Viewed by 3217
Abstract
Traditional computational fluid dynamics (CFD) methods are usually used to obtain information about the flow field over an airfoil by solving the Navier–Stokes equations for the mesh with boundary conditions. These methods are usually costly and time-consuming. In this study, the pix2pix method, [...] Read more.
Traditional computational fluid dynamics (CFD) methods are usually used to obtain information about the flow field over an airfoil by solving the Navier–Stokes equations for the mesh with boundary conditions. These methods are usually costly and time-consuming. In this study, the pix2pix method, which utilizes conditional generative adversarial networks (cGANs) for image-to-image translation, and a deep neural network (DNN) method were used to predict the airfoil flow field and aerodynamic performance for a wind turbine blade with various shapes, Reynolds numbers, and angles of attack. Pix2pix is a universal solution to the image-to-image translation problem that utilizes cGANs. It was successfully implemented to predict the airfoil flow field using fully implicit high-resolution scheme-based compressible CFD codes with genetic algorithms. The results showed that the vortical flow fields of the thick airfoils could be predicted well using the pix2pix method as a result of deep learning. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics for Future Energies)
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20 pages, 6687 KiB  
Article
Analysis of an Elasto-Hydrodynamic Seal by Using the Reynolds Equation
by Sevki Cesmeci, Karthik Reddy Lyathakula, Mohammad Fuad Hassan, Shuangbiao Liu, Hanping Xu and Jing Tang
Appl. Sci. 2022, 12(19), 9501; https://doi.org/10.3390/app12199501 - 22 Sep 2022
Cited by 6 | Viewed by 2150
Abstract
This paper reports numerical studies of an Elasto-Hydrodynamic (EHD) seal, which is being developed for supercritical CO2 (sCO2) turbomachinery applications. Current sCO2 turbomachinery suffers from high leakage rates, which is creating a major roadblock to the full realization of [...] Read more.
This paper reports numerical studies of an Elasto-Hydrodynamic (EHD) seal, which is being developed for supercritical CO2 (sCO2) turbomachinery applications. Current sCO2 turbomachinery suffers from high leakage rates, which is creating a major roadblock to the full realization of sCO2 power technology. The high leakage rates not only penalize the efficiencies but also create environmental concerns due to greenhouse effects caused by the increased CO2 discharge to the atmosphere. The proposed EHD seal needs to work at elevated pressures (10–35 MPa) and temperatures (350–700 °C) with low leakage and minimal wear. The unique mechanism of the EHD seal provides a self-regulated constriction effect to restrict the flow without substantial material contact, thereby minimizing leakage and wear. This work utilizes a physics-based modeling approach. The flow through the gradually narrowing seal clearance is modeled by the well-known Reynolds equation in EHD lubrication theory, while the deformation of the seal is modeled by using the governing equations of three-dimensional solid mechanics. As for the solution methodology, COMSOL’s Thin-Film Flow and Solid Mechanics modules were employed with their powerful capabilities. The numerical results were presented and discussed. It was observed that the Reynolds equation fully coupled with the surface deformation was able to successfully capture the constriction effect. The maximum and minimum leakages were calculated to be 2.25 g/s and 0.1 g/s at P = 5.5 MPa and P = 11 MPa for the design seal, respectively. It was interesting to observe that the seal leakage followed a quadratic trend with increasing pressure differential, which can become advantageous for high-pressure applications such as sCO2 power generation technology. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics for Future Energies)
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16 pages, 8986 KiB  
Article
Numerical Study on Vortical Flow Structure and Performance Enhancement of Centrifugal Compressor Impeller
by Seongbin Hong, Jophous Mugabi and Jae-Ho Jeong
Appl. Sci. 2022, 12(15), 7755; https://doi.org/10.3390/app12157755 - 1 Aug 2022
Cited by 3 | Viewed by 2413
Abstract
The performance and efficiency of a centrifugal compressor are usually affected by the highly complex 3-dimensional flow structures which develop in the flow field of the compressor. Several experiments and research using numerical analysis have been reported, however, there are still many unknown [...] Read more.
The performance and efficiency of a centrifugal compressor are usually affected by the highly complex 3-dimensional flow structures which develop in the flow field of the compressor. Several experiments and research using numerical analysis have been reported, however, there are still many unknown physical phenomena that need to be studied, in order to optimize the design and improve the efficiency of turbomachines, especially those installed on hydrogen-powered fuel cell electric vehicles (FCEVs). In this study, the 3-dimensional vortex structures were analyzed using the critical-point theory and the probabilistic definitions, for an air supply device mounted on the commercial hydrogen FCEVs. The behavior of the complex 3-dimensional vortex structures at the design flow rate and low flow rate were elucidated. A tip leakage vortex was observed to develop at the leading edge of the main blade at all flow rates, which caused interference to the splitter blade. At 60% of the design flow rate, a vortex breakdown occurred at the tip leakage vortex near the leading edge of the main blade, and a reverse flow at 50% chord length of the main blade’s suction surface. The boundary layer which developed at the leading edge of the main blade’s suction surface at all flow rates led to the creation of a hub separation vortex by interfering with the boundary layer developed at the hub surface as a result of the centrifugal force. In addition, the boundary layer developed at the hub and shroud surface created a horseshoe vortex as it moved downstream and interfered with the leading edge of the main blade and splitter blade. It was confirmed that the behavior of the tip leakage, hub separation, and horseshoe vortex structures determined the aerodynamic performance of the centrifugal compressor. The average pressure difference improved by 1.47% of the entire flow rate after optimizing the compressor design. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics for Future Energies)
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19 pages, 16246 KiB  
Article
CFD-Based In-Depth Investigation of the Effects of the Shape and Layout of a Vortex Generator on the Aerodynamic Performance of a Multi-MW Wind Turbine
by Hyeon-Gi Moon, Sunho Park, Kwangtae Ha and Jae-Ho Jeong
Appl. Sci. 2021, 11(22), 10764; https://doi.org/10.3390/app112210764 - 15 Nov 2021
Cited by 5 | Viewed by 3199
Abstract
Thick airfoils are conventionally adopted in the blade root region of a wind turbine to ensure structural safety under extreme conditions, despite the resulting power loss. To prevent this loss, a passive flow control device known as a vortex generator (VG) is installed [...] Read more.
Thick airfoils are conventionally adopted in the blade root region of a wind turbine to ensure structural safety under extreme conditions, despite the resulting power loss. To prevent this loss, a passive flow control device known as a vortex generator (VG) is installed at the starting point of the stall to control the flow field near the wall of the suction surface. In this study, we used computational fluid dynamics (CFD) to investigate the aerodynamic characteristics induced as a result of the shape and layout of the VG on a multi-MW wind turbine blade. The separated and vortical flow behavior on the suction surface of the wind turbine blade equipped with VGs was captured by the Reynolds-averaged Navier–Stokes (RANS) steady-flow simulation. The parametric sensitivity study of the VG shape parameters such as the chord-wise length, height, and interval of the fair of VGs was conducted using thick DU airfoil on the blade inboard area. Based on these results, the response surface method (RSM) was used to investigate the influence of the design parameters of the VG. Based on the CFD results, the VG design parameters were selected by considering the lift coefficient and vorticity above the trailing edge. The maximum vorticity from the trailing edge of the selected VG and the lift coefficient were 55.7% and 0.42% higher, respectively, than the average. The selected VG design and layout were adopted for a multi-MW wind turbine and reduced stall occurrence in the blade root area, as predicted by the simulation results. The VG improved the aerodynamic performance of the multi-MW wind turbine by 2.8% at the rated wind speed. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics for Future Energies)
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23 pages, 11968 KiB  
Article
Three-Dimensional Numerical Investigations of the Flow Pattern and Evolution of the Horseshoe Vortex at a Circular Pier during the Development of a Scour Hole
by Ahmed M. Helmi and Ahmed H. Shehata
Appl. Sci. 2021, 11(15), 6898; https://doi.org/10.3390/app11156898 - 27 Jul 2021
Cited by 4 | Viewed by 2273
Abstract
In the current study, a three-dimensional CFD model is utilized to investigate the variation of the flow structure and bed shear stress at a single cylindrical pier during scour development. The scour development is presented by seven solidified geometries of the scour hole, [...] Read more.
In the current study, a three-dimensional CFD model is utilized to investigate the variation of the flow structure and bed shear stress at a single cylindrical pier during scour development. The scour development is presented by seven solidified geometries of the scour hole, collected during previous experimental work at different scour stages. Different turbulence models are evaluated and the (k-ω) model is chosen due to its relative accuracy in capturing the flow oscillation and vortex shedding at the pier downstream side with personal computer computational and storage resources. The numerical results are verified against dimensionless parameters from different previous experimental works. This research describes in detail the flow structure and bed shear stress variations through seven stages of the scour hole development. The dimensionless area-averaged circulation coefficient (Ψi) is developed to evaluate the changes in the vortex strength through the scouring process by eliminating the calculation area effect. It was concluded that the circulation in the (Y) direction is the main driving factor in the development of the scour hole more than the circulation in the (X) direction. The ratio between the horseshoe vortex (HV) mean size and the scouring depth (DV/dS) in addition to the location of the maximum bed shear stress are investigated during different stages of the scour development. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics for Future Energies)
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