Article
Engineering, Aerospace
Nicholas Zhu, Zheng Zhang, Ebenezer Gnanamanickam, J. Gordon Leishman
Summary: The turbulent airwakes generated by a typical navy frigate were investigated using a low-speed wind tunnel. High-speed stereoscopic particle image velocimetry was performed at various spanwise planes over the flight deck. The results revealed the shedding of turbulent structures from the funnel and superstructure edges, as well as the three-dimensional bistable behavior of the flow recirculation region behind the superstructure. Additionally, a pair of vortices near the stern exhibited low-frequency bistable dynamics, with the bistable flow recirculation region influencing the low-frequency behavior of other major flow features.
Article
Computer Science, Interdisciplinary Applications
Brian C. Vermeire
Summary: This study presents a framework for implicit large eddy simulation (ILES) of incompressible flows by combining the entropically damped artificial compressibility (EDAC) method with the flux reconstruction (FR) approach. Experimental results demonstrate that the method is accurate and stable for low-order solutions, while higher-order solutions exhibit significantly higher accuracy and lower divergence error compared to reference direct numerical simulation.
COMPUTERS & FLUIDS
(2024)
Article
Mathematics, Applied
Di Sun, Feng Qu, Junqiang Bai
Summary: In this study, an Implicit Large Eddy Simulation (ILES) method based on all-speed schemes in a framework of the finite volume method is analyzed for the simulation of complex flow structures in both high and low Mach numbers regimes. The method shows good accuracy in capturing compressible phenomena and small turbulent structures. The application of the method to cylinder flow and transonic cavity flow yields results in agreement with previous studies, indicating its promising potential for complex engineering flow problems.
COMPUTERS & MATHEMATICS WITH APPLICATIONS
(2022)
Review
Engineering, Marine
Blanca Pena, Luofeng Huang
Summary: Ship operations are influenced by turbulent regimes that have a significant impact on hydrodynamic characteristics. Computational technologies have advanced to allow for detailed numerical simulations of turbulent ship flows, but the high computational costs and lack of updated recommendations for turbulence modeling present challenges. This paper reviews the current state-of-the-art turbulence modeling for ship hydrodynamic applications, introducing various approaches and discussing their applicability and limitations in different ship simulation scenarios. The goal is to provide guidance for CFD users in selecting turbulence modeling strategies and advancing the field.
Article
Computer Science, Interdisciplinary Applications
Youming Tai, Tomoaki Watanabe, Koji Nagata
Summary: Implicit large eddy simulation (ILES) is evaluated for passive scalar transfer in compressible turbulence, showing good agreement with the direct numerical simulation (DNS) and successfully capturing scalar transport by turbulent velocity fluctuations.
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS
(2021)
Article
Thermodynamics
H. S. Park, D. Linton, B. Thornber
Summary: Computational fluid dynamics simulations of a rotorcraft fuselage and ship airwake were conducted using an immersed boundary method in OpenFOAM. The improved wall function in the immersed boundary method enhanced the accuracy and computational speed of the solver, and the simulation results were validated against experimental measurements and previously published computational data.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2022)
Article
Engineering, Aerospace
Daniel J. Garmann, Miguel R. Visbal
Summary: This high-fidelity numerical study aims to expand the concept of pitch/plunge equivalence to finite, swept wings undergoing deep-dynamic stall. The study evaluates the effects of pitch-induced apparent camber on the wing and its impact on flow structure, surface topology, and aerodynamic loading. The research finds that regardless of the motion type or rate, the wing experiences dynamic tip stall, with a faster development and evolution in the case of pitch motion. The study also explores the corrections to lift and moment coefficients and discovers that the corrected plunge-equivalent histories collapse the force and moment responses between pitch and plunge cases, despite the delayed behavior of the flow structure.
Article
Computer Science, Interdisciplinary Applications
Wenjin Zhao, Guiyu Cao, Jianchun Wang, Kun Xu
Summary: This study validates the effectiveness of high-order non-compact and compact reconstruction in turbulence simulation using the high-order gas-kinetic scheme (HGKS). The accuracy of HGKS is confirmed through numerical simulations of three-dimensional density perturbation advection. Both non-compact 7th-order and compact 5th-order reconstruction schemes are shown to provide accurate solutions for turbulent flows.
COMPUTERS & FLUIDS
(2023)
Article
Engineering, Aerospace
Caleb J. Barnes, Miguel R. Visbal
Summary: This paper presents a computational study on the unsteady transonic effects on a supercritical laminar airfoil. The results show that shock and boundary layer behaviors are highly sensitive to the change in angle of attack, leading to significant variations in flow structure and laminar separation bubbles.
Article
Construction & Building Technology
Andrea Crivellini, Alessandra Nigro, Alessandro Colombo, Antonio Ghidoni, Gianmaria Noventa, Andrea Cimarelli, Roberto Corsini
Summary: This paper presents the numerical results of the flow around a 5:1 rectangular cylinder under different conditions. The simulations demonstrate the accuracy of the results by comparing with experimental data and other simulation results. Additionally, various factors affecting the accuracy of the results are investigated.
WIND AND STRUCTURES
(2022)
Article
Thermodynamics
Sergio Croquer, Olivier Lamberts, Sebastien Poncet, Stephane Moreau, Yann Bartosiewicz
Summary: This study investigates the flow topology in the mixing chamber of a supersonic ejector using Large Eddy Simulation (LES). The results show that the mixing layer transitions from laminar to turbulent and vortices are identified in the first quarter of the mixing chamber. The study also reveals the occurrence of shock train towards the end of the mixing chamber, enhancing mixing.
APPLIED THERMAL ENGINEERING
(2022)
Article
Environmental Sciences
Andrew M. Thomas, Robert J. Kurzeja
Summary: Typical dispersion simulations use mesoscale models with grid spacing greater than 1 km, while advances in computing power have allowed for the use of Large Eddy Simulations (LES) with grid spacing less than 100 m. In this study, the WRF mesoscale/LES model and the HYSPLIT particle dispersion model were used to simulate SF6 transport, using a grayscale-aware scheme with different nest sizes. The results showed that the WRF/LES simulation was in agreement with meteorological observations, but the HYSPLIT SF6 simulations had insufficient subgrid turbulence kinetic energy, leading to over predictions of surface SF6 concentration and insufficient vertical transport. The best agreement with observations was obtained by combining the WRF/LES large-scale and subgrid turbulence with a HYSPLIT parameterized turbulence profile.
ATMOSPHERIC ENVIRONMENT
(2023)
Article
Engineering, Marine
Ali Zamiri, Jin Taek Chung
Summary: The airwake characteristics around a ship body were investigated using delayed detached eddy simulation (DDES) technique. The influence of the bow part of the ship and wind direction on the turbulent flow characteristics of the ship deck airwake was studied. Numerical simulations were performed for different ship models and wind direction angles. The results showed that the deck flow-field is not influenced by the bow of the ship, but the airwake flow is significantly affected by the wind direction angle.
Article
Thermodynamics
D. Dupuy, A. Perrot, N. Odier, L. Y. M. Gicquel, F. Duchaine
Summary: The study shows that introducing spatial inhomogeneity and turbulent injection can significantly improve the predictions of cooling effectiveness in film-cooling systems. Spatial inhomogeneity is crucial for near-hole flow behavior, while turbulent injection plays an important role when immediate transition is not triggered.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Mechanics
A. Golsa Tabe Jamaat, B. Yuji Hattori
Summary: In this study, a neural network is implemented to establish the relationship between the resolved-scale flow field and the subgrid-scale stress for the Burgers equation. The training datasets are obtained by filtering the direct numerical simulation results and different sets of input parameters are considered. The a priori and a posteriori tests show that the neural network models have high correlation coefficients with the filtered DNS data and can produce stable results without any stabilization techniques.
Article
Thermodynamics
H. S. Park, D. Linton, B. Thornber
Summary: Computational fluid dynamics simulations of a rotorcraft fuselage and ship airwake were conducted using an immersed boundary method in OpenFOAM. The improved wall function in the immersed boundary method enhanced the accuracy and computational speed of the solver, and the simulation results were validated against experimental measurements and previously published computational data.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2022)
Article
Mechanics
Talib Dbouk, Dimitris Drikakis
Summary: This study presents a computational fluid dynamics-based epidemic model that explores the relationship between weather conditions and airborne virus transmission dynamics. The model examines the impact of weather seasonality on airborne virus transmission and pandemic outbreaks, using multiple scenarios of the COVID-19 fifth wave in London, United Kingdom to demonstrate potential peak and occurrence period. The study highlights the significance of fluid dynamics and computational modeling in advancing epidemiological models.
Article
Mechanics
Ioannis W. Kokkinakis, Dimitris Drikakis
Summary: We investigated the impact of rocket exhaust gases on atmospheric pollution through computational fluid dynamics simulations, and found that the cumulative effect of frequent rocket launches on climate should not be underestimated.
Article
Mechanics
Ioannis W. Kokkinakis, Dimitris Drikakis
Summary: This study examines the effects of nuclear blasts on humans inside buildings in moderately damaged areas. The results show that the forces exerted by the gusts of wind created inside the rooms can lift and throw a person off the ground, posing a risk of severe injury or death. However, there are specific areas within the rooms where individuals can avoid exposure to the highest wind forces.
Article
Mathematics
Konstantinos Poulinakis, Dimitris Drikakis, Ioannis W. Kokkinakis, Stephen Michael Spottswood
Summary: This study compares machine-learning methods and cubic splines on their ability to handle sparse and noisy training data. The results show that cubic splines provide more precise interpolation than deep neural networks and multivariate adaptive regression splines with very sparse data. However, machine-learning models show robustness to noise and can outperform splines after reaching a threshold of training data. The study aims to provide a general framework for interpolating one-dimensional signals, often obtained from complex scientific simulations or laboratory experiments.
Article
Mechanics
Michael Groom, Ben Thornber
Summary: The effects of initial conditions on the evolution of the Richtmyer-Meshkov instability (RMI) are analyzed using numerical simulations and compared with experimental results. Various measures of mixing layer width and decay rate of fluctuating kinetic energy are used to explore the effects of initial conditions, and good agreement is found with experimental data. The results demonstrate differences between broadband and narrowband perturbations and emphasize the importance of considering the concentration field when inferring properties based on the velocity field.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Ioannis W. Kokkinakis, Dimitris Drikakis
Summary: This study investigates indoor explosions and their impact on humans. It challenges the standard approach that blast overpressure is the main determinant of trauma and injury. Instead, it shows that the wind force generated behind the blast can have a greater effect on humans, even at low blast overpressures.
Article
Mechanics
Ioannis W. Kokkinakis, George Khujadze, Dimitris Drikakis, S. Michael Spottswood
Summary: We conducted a wavelet analysis on supersonic shock-boundary-layer interaction using orthogonal anisotropic wavelets. By decomposing the flow vorticity field into coherent and incoherent contributions through thresholding of the wavelet coefficients, we found that the statistics of the coherent part of vorticity are similar to the statistics of the total field. Our study aims to enhance understanding of the shock-boundary-layer interaction, the role of vorticity, and the relationship between the flow's coherent and incoherent vorticity components with the near-wall sound. Our analysis reveals a significant correlation between the incoherent part of vorticity components and wall-pressure fluctuations.
Article
Mechanics
Ioannis W. Kokkinakis, Dimitris Drikakis, S. Michael Spottswood, Kirk R. Brouwer, Zachary B. Riley
Summary: This paper investigates the interaction between an oblique shock wave and a supersonic turbulent boundary layer over a thin panel surface, focusing on shock-boundary layer interaction and panel buckling. High-order numerical simulations were conducted to examine various static two-dimensional surface deformations commonly encountered in experiments. The results show that the mean and root mean square pressure are affected by about 10% at the maximum deformation amplitude location along the panel midspan. The deformation modes disrupt the spanwise distribution of the mean pressure and induce a characteristic bending of the spanwise distribution.
Article
Mechanics
Konstantinos Ritos, Dimitris Drikakis, Ioannis W. Kokkinakis
Summary: This paper presents simulations of virus droplets in a typical cruiser's cabin and investigates the effects of ventilation rates and positions of the coughing person. The study highlights the importance of accurate simulation by including evaporation models. It suggests that a higher ventilation rate may not always be the best strategy to prevent the spread of airborne diseases, and proposes using ventilation systems with medium flow rates for occupied cabins to minimize droplet spreading while maintaining good ventilation.
Article
Mathematics
Nicholas Christakis, Dimitris Drikakis
Summary: This paper discusses the use of unsupervised learning to classify particle-like dispersion and its relevance to various applications such as virus transmission and atmospheric pollution. The RUN-ICON algorithm of unsupervised learning is applied to classify particle spread with higher confidence and lower uncertainty compared to other algorithms, even in the presence of noise. The combination of unsupervised learning and the RUN-ICON algorithm provides a tool for studying particle dynamics and their impact on air quality, health, and climate.
Article
Mathematics
Nicholas Christakis, Dimitris Drikakis
Summary: This paper presents the development of a novel algorithm called RUN-ICON for unsupervised learning. It aims to improve the reliability and confidence of unsupervised clustering by leveraging the K-means++ method and introducing novel metrics. The algorithm has notable characteristics such as robustness, high-quality clustering, automation, and flexibility, and extensive testing has demonstrated its capability to determine the optimal number of clusters under different scenarios. It will soon undergo rigorous testing in real-world scenarios to further prove its effectiveness.
Review
Physics, Fluids & Plasmas
Dimitris Drikakis, Filippos Sofos
Summary: The significant growth of artificial intelligence methods in machine learning and deep learning has created opportunities for the application of fluid dynamics in science, engineering, and medicine. However, developing AI methods for fluid dynamics poses challenges due to the limitations of data availability for scientific, engineering, and biomedical problems. This paper reviews the research on machine learning and deep learning for fluid dynamics, discusses algorithmic challenges, and explores potential future directions.
Article
Engineering, Aerospace
Jack Heesung Park, Daniel Linton, Ben Thornber
Summary: Computational fluid dynamics simulations are conducted to analyze the flow around the ROBIN-mod7 fuselage with a pressure-sensitive paint rotor. A comprehensive analysis of the helicopter configuration is carried out for hovering flight condition, including simulations of isolated fuselage, isolated rotor, and rotor-fuselage cases. The validation shows good agreement with experimental measurements and computational data from the literature. The results demonstrate an equivalent level of accuracy to previous high-fidelity simulations at a fraction of the computational expenses.
JOURNAL OF THE AMERICAN HELICOPTER SOCIETY
(2023)
Review
Energy & Fuels
Dimitris Drikakis, Talib Dbouk
Summary: This paper discusses the technology challenges in the wind and solar sectors and the role of computational science in addressing them. The challenges in wind energy include understanding atmospheric flow physics, complex wakes, aeroelastic effects, and wind farm optimization. Concentrated solar power technologies require optimal configuration for efficiency, durability, and reducing heat losses. Computational fluid dynamics and heat transfer have advanced in terms of numerical methods and physics-based models. However, further development is needed to accurately and efficiently design complex systems and forecast performance.
