Article
Mechanics
Matthew A. Subrahmanyam, Brian J. Cantwell, Juan J. Alonso
Summary: This paper introduces a mixing length model for turbulent shear stress in pipe flow and provides a universal velocity profile. The velocity profile accurately approximates both experimental and simulated data in various flow conditions, making it significant for studying the statistical properties of flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Xinxian Zhang, Tomoaki Watanabe, Koji Nagata
Summary: In this study, direct numerical simulations of temporally developing turbulent boundary layers were used to investigate the Reynolds number dependence of the turbulent/non-turbulent interface (TNTI) layer. The results revealed the mean thicknesses of the TNTI layer, turbulent sublayer, and viscous superlayer, as well as the characteristics of the irrotational boundary. It was found that the mean shear effects near the TNTI layer are not significant and that the turbulence under the TNTI layer tends to be isotropic at high Reynolds numbers.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Christoph Wenzel, Tobias Gibis, Markus Kloker, Ulrich Rist
Summary: This study quantitatively evaluates the Reynolds analogy factor for self-similar turbulent boundary layers with pressure gradients using direct numerical simulation. The factor is found to increase for adverse-pressure-gradient cases and decrease for favourable-pressure-gradient cases. Mach number has a small influence, and no dependency on Reynolds number was observed. The effects of pressure gradients can be approximated by an analytical relation derived by So in incompressible flow.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
J. C. Klewicki
Summary: High resolution direct numerical simulation data are used to investigate the similarity solutions for mean velocity and Reynolds shear stress in turbulent channel flow. The analysis yields an invariant form of the mean momentum equation valid over a significant portion of the flow domain. The results provide insights into the development of wall-flow models and support conjectures regarding the behavior of similarity parameters at large Reynolds numbers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Andrea Andreolli, Davide Gatti, Ricardo Vinuesa, Ramis Oerlue, Philipp Schlatter
Summary: The presence of very-large-scale motions in wall-bounded turbulent flows is commonly associated with the superposition of large scales at the wall and the modulation of small-scale near-wall turbulence. This study challenges the current understanding by selectively suppressing either superposition or amplitude modulation and studying the remaining phenomenon. The results indicate that there is still a correlation between the amplitude of small scales near the wall and the large-scale signal in the outer flow even when near-wall large-scale motions are suppressed.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Christoph Wenzel, Tobias Gibis, Markus Kloker
Summary: This paper presents a comprehensive analysis of momentum and energy transfer in compressible turbulent boundary layers based on integral identities. The superordinate influences of compressibility, wall heat transfer, and pressure gradient on the governing equations are identified and visualized using data from direct numerical simulations. Newly formulated identities for skin-friction coefficient and specific heat-transfer coefficient are derived, allowing for comparison of different cases and design of turbulent boundary-layer cases with specific behavior. The proposed formulation of the Eckert number serves as a similarity parameter, mapping cases with different Mach numbers and wall heat transfer conditions.
JOURNAL OF FLUID MECHANICS
(2021)
Review
Engineering, Aerospace
William J. Devenport, K. Todd Lowe
Summary: This article presents a review of historical and recent developments in the understanding of equilibrium and non-equilibrium turbulent boundary layers at incompressible high-Reynolds number conditions. The review focuses on the mean flow, turbulence stress fields, and instantaneous structure, discussing smooth wall and rough wall boundary layers as well as equilibrium and non-equilibrium two-dimensional flows. It concludes with a detailed discussion of boundary layer development in skewed, three-dimensional flows over smooth walls.
PROGRESS IN AEROSPACE SCIENCES
(2022)
Article
Mechanics
K. Matsuno, S. K. Lele
Summary: The study reveals that at high Mach numbers, the spatial scales of eddying motions in mixing layers progressively decrease, forming independent layers of eddying motions, thereby reducing the effective velocity scale for turbulent motions and suppressing Reynolds stresses, turbulent kinetic energy production and dissipation, and the growth rate of mixing-layer thickness.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Mustafa Z. Yousif, Meng Zhang, Linqi Yu, Ricardo Vinuesa, HeeChang Lim
Summary: This study proposes a new deep-learning-based method for generating turbulent inflow conditions in spatially developing turbulent boundary layer (TBL) simulations. The model combines a transformer and a multiscale-enhanced super-resolution generative adversarial network to predict velocity fields of the TBL at different planes. The model shows remarkable accuracy in predicting velocity fields and reproducing turbulence statistics. Furthermore, it demonstrates the effectiveness of using transformer-based models and generative adversarial networks for various turbulence-related problems.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Xuebo Li, Nicholas Hutchins, Xiaojing Zheng, Ivan Marusic, Woutijn J. Baars
Summary: A large-scale array of measuring instruments was used to study the statistical structure of turbulence structures in different stability conditions. The researchers found a self-similar range of turbulence structures and analyzed the scale-dependent inclination angle in the streamwise/wall-normal plane. The results showed that the inclination angle and aspect ratio of the structures were highly sensitive to the stability parameter.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Yukio Kaneda, Yoshinobu Yamamoto
Summary: This paper extends Kolmogorov's local similarity hypotheses to include the influence of mean shear on the statistics of fluctuating velocity. The moments of the velocity gradients are determined by the local turbulent energy dissipation rate, kinematic viscosity, and parameter gamma. The anisotropy of moments decreases approximately in proportion to gamma when gamma is small in an appropriate sense.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
G. A. Gerolymos, I. Vallet
Summary: The paper investigates the effects of Mach number on pressure fluctuations in compressible turbulent plane channel flow. Using direct numerical simulation, the study finds strong Mach number effects near the wall, with increased wall root-mean-square pressure fluctuations but slightly decreased peak level across the channel. The research also reveals the existence of complex wave systems and wave-packet-like structures, which appear to be responsible for compensating the negative correlation coefficient between pressure fluctuations and velocity fluctuations.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Cheng Cheng, Wei Shyy, Lin Fu
Summary: A new methodology was developed to assess the distribution of wall-attached eddies, revealing that the SIAs depend on the Reynolds number at low and medium Reynolds numbers, saturating at 45 degrees as the Reynolds number increases. The average SIA reported in previous experimental studies was shown to be the result of the additive effect of multi-scale attached eddies.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
X. Y. Jiang, D. W. Gu, C. B. Lee, C. R. Smith, P. F. Linden
Summary: The study explores the laminar-turbulent transition in boundary layers by investigating the evolution of flow structures from 3-D waves to Lambda-vortices. Through numerical simulations of K-regime and bypass transitions, the process of wave-warping and vortex dynamics is examined. The research suggests that adverse pressure gradient conditions lead to a more rapid evolution and stronger viscous-inviscid interaction, ultimately resulting in the development of high-shear layers and warped wave fronts.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
M. Wasy Akhtar, Rodolfo Ostilla-Monico
Summary: Direct numerical simulations were conducted to study the effect of modulated forcing on turbulent shear flows in non-rotating and rotating plane Couette flow. The results showed that the shear at the plates was independent of the forcing frequency, and anti-cyclonic rotation significantly changed the system's response to periodic forcing.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Joseph I. Ibrahim, Qiang Yang, Patrick Doohan, Yongyun Hwang
JOURNAL OF FLUID MECHANICS
(2019)
Article
Mechanics
Patrick Doohan, Ashley P. Willis, Yongyun Hwang
JOURNAL OF FLUID MECHANICS
(2019)
Article
Mechanics
Patrick Doohan, Yacine Bengana, Qiang Yang, Ashley P. Willis, Yongyun Hwang
Summary: The computation of invariant solutions and the visualization of the associated state space are important for understanding the transition and self-sustaining process in wall-bounded shear flows. However, in multi-scale turbulence, the lack of scale interaction processes captured by invariant solutions prevents finding a solution that resembles turbulent state. Nevertheless, there is one solution that captures the two-scale energetics and scale interaction process of turbulence.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Immunology
Rob Johnson, Bimandra Djaafara, David Haw, Patrick Doohan, Giovanni Forchini, Matteo Pianella, Neil Ferguson, Peter C. Smith, Katharina D. Hauck
Summary: This study estimated the socio-economic value of booster vaccination by comparing the costs with and without boosters using simulation modelling. The results showed that booster vaccination can significantly reduce the need for costly non-pharmaceutical interventions and bring substantial societal benefits. It is recommended to consider all socio-economic costs, not just the number of averted deaths, in policy decision-making and vaccination evaluation.
Article
Infectious Diseases
Thomas Rawson, Patrick Doohan, Katharina Hauck, Kris A. Murray, Neil Ferguson
Summary: A review of existing literature indicates that climate change will have a significant impact on the spread of communicable diseases. However, there is a lack of research specifically focusing on how this will be observed in the countries of the Gulf Cooperation Council (GCC). This report highlights the unique public health challenges faced by the GCC countries in the future and emphasizes the need for increased investment in public health research and disease surveillance.
Article
Multidisciplinary Sciences
Alexandra B. Hogan, Patrick Doohan, Sean L. Wu, Daniela Olivera Mesa, Jaspreet Toor, Oliver J. Watson, Peter Winskill, Giovanni Charles, Gregory Barnsley, Eleanor M. Riley, David S. Khoury, Neil M. Ferguson, Azra C. Ghani
Summary: This study uses a model-based approach to estimate that using a variant-matched booster vaccine could prevent nearly twice as many hospitalizations and deaths as using an ancestral booster. Updated vaccines may be needed due to the ongoing evolution of the virus.
NATURE COMMUNICATIONS
(2023)
Article
Computer Science, Interdisciplinary Applications
David J. Haw, Giovanni Forchini, Patrick Doohan, Paula Christen, Matteo Pianella, Robert Johnson, Sumali Bajaj, Alexandra B. Hogan, Peter Winskill, Marisa Miraldo, Peter J. White, Azra C. Ghani, Neil M. Ferguson, Peter C. Smith, Katharina D. Hauck
Summary: DAEDALUS is a comprehensive model that studies the trade-off between economic, social and health outcomes in pandemic management. It combines epidemiological and economic models to identify strategies that optimize economic production while constraining infections. The application of this model to the United Kingdom shows economic gains and allows important services to remain active.
NATURE COMPUTATIONAL SCIENCE
(2022)