Article
Meteorology & Atmospheric Sciences
Srinidhi N. Gadde, Anja Stieren, Richard J. A. M. Stevens
Summary: The study compares the performance of different SGS models for large-eddy simulations of the atmospheric boundary layer. It finds that the AMD and LASD models capture velocity profiles and turbulence energy spectra better than the Smagorinsky model. The computational overhead of the AMD and LASD models is slightly higher than the Smagorinsky model, with the AMD model being more efficient for large-scale simulations.
BOUNDARY-LAYER METEOROLOGY
(2021)
Article
Mechanics
Jahrul Alam
Summary: This study reveals that vortex stretching and the second invariant of the velocity gradient tensor can provide a scale-adaptive parameterization of the subgrid-scale energy fluxes in wind turbine wakes. Numerical results from a utility-scale wind farm show that the spectrum of wind power fluctuations follows a power law distribution with a logarithmic slope of -5/3. Furthermore, the modulation of wind power fluctuations is influenced by incoming turbulence and wake interactions in wind farms.
Article
Computer Science, Interdisciplinary Applications
Oumaima Lamaakel, Georgios Matheou
Summary: In large-eddy simulations, utilizing a computational-domain translation velocity can improve performance, but it is important to note that the discretization errors are proportional to the product of the local translation velocity and the truncation error. The flow statistics in LES of convection may show different characteristics in different scenarios.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Geochemistry & Geophysics
Mary-Jane M. Bopape, Robert S. Plane, Omduth Coceal, Georgios A. Efstathiou, Maria Valdivieso
Summary: Dynamic subgrid models, such as the Lagrangian-Averaged-Scale-Dependent (LASD) model, are increasingly used in simulations of the atmospheric boundary layer. This paper investigates the impact of stability functions on the behavior of the LASD model in convective boundary layer simulations at different resolutions. Results show that while the use of stability functions improves the model's performance in the grey zone regime, a careful treatment of stability functions in the calculation of dynamic parameters is found to be unnecessary in practice.
ATMOSPHERIC SCIENCE LETTERS
(2021)
Article
Meteorology & Atmospheric Sciences
Yahua Wang, Xiaoping Cheng, Jianfang Fei, Bowen Zhou
Summary: This study investigates the numerical gray zone of boundary layer turbulence of shallow cumulus-topped boundary layer (SCTBL) at kilometer- and subkilometer-scale resolutions. The study determines the gray zone scale based on analysis of a simulated classic SCTBL and reveals the link between the cloud layer and the underlying mixed layer. A posteriori simulations are performed to evaluate the performance of a scale-adaptive planetary boundary layer (PBL) scheme and suggest the need for modifications under shallow cumulus-topped conditions.
JOURNAL OF THE ATMOSPHERIC SCIENCES
(2022)
Article
Meteorology & Atmospheric Sciences
Bowen Zhou, Yuhuan Li, Shiguang Miao
Summary: A scale-adaptive model is developed for the representation of dry convective boundary layer (CBL) turbulence, blending a planetary boundary layer (PBL) scheme with a large-eddy simulation (LES) closure. The new model accounts for vertical variations of turbulent length scales and performs well under various CBL stability conditions. Implemented into a community atmospheric model, it shows advantages over established gray zone models under weakly unstable and near neutral CBL conditions.
JOURNAL OF THE ATMOSPHERIC SCIENCES
(2021)
Article
Engineering, Civil
Quentin Bucquet, Isabelle Calmet, Laurent Perret, Magdalena Mache
Summary: This work assesses the performance of the drag-porosity model implemented in ARPS atmospheric Large-Eddy Simulation (LES) solver for simulating the atmospheric boundary layer over the urban canopy. The flow over an idealized urban canopy consisting of cubes with various packing densities is investigated. The model is able to reproduce the key features of the flow over urban terrain, including turbulent coherent structures and their characteristic scales.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2023)
Article
Environmental Sciences
Yuting Wang, Yong-Feng Ma, Domingo Munoz-Esparza, Cathy W. Y. Li, Mary Barth, Tao Wang, Guy P. Brasseur
Summary: Global and regional chemical transport models assume complete mixing of chemical species within each grid box, but localized sources and topography can lead to segregation of species. Large-eddy simulations conducted in Hong Kong Island reveal that emission inhomogeneity and turbulent motions due to topography increase segregation intensity. This segregation effect reduces ozone formation by 8%-12% compared to complete mixing, suggesting that coarse-resolution models may overestimate surface ozone levels.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2021)
Article
Green & Sustainable Science & Technology
Brooke J. Stanislawski, Regis Thedin, Ashesh Sharma, Emmanuel Branlard, Ganesh Vijayakumar, Michael A. Sprague
Summary: As wind turbines become larger, the fluctuations in inflow have a significant impact on structural loading. The integral length scale, which represents the average size of the largest turbulent eddies, characterizes these fluctuations. Current design standards do not account for the varying integral length scales in turbine inflows. Using large-eddy simulations, we investigate the effects of turbulence with varying integral length scales on the loads of a 15-MW wind turbine. The results show that turbulence has a much greater impact on rotor and tower loads compared to mean shear profiles. Increasing the integral length scale can reduce blade root flapwise moments and rotor and tower loads. However, increasing the integral length scale beyond a certain point increases other loads and decreases some moments. Additionally, turbulence intensity has a larger influence on turbine loads than integral length scales. This study suggests that design standards should consider the varying integral length scales for accurate characterization of wind turbine loading in turbulent inflow conditions.
Review
Agronomy
Manuel Helbig, Tobias Gerken, Eric R. Beamesderfer, Dennis D. Baldocchi, Tirtha Banerjee, Sebastien C. Biraud, William O. J. Brown, Nathaniel A. Brunsell, Elizabeth A. Burakowski, Sean P. Burns, Brian J. Butterworth, W. Stephen Chan, Kenneth J. Davis, Ankur R. Desai, Jose D. Fuentes, David Y. Hollinger, Natascha Kljun, Matthias Mauder, Kimberly A. Novick, John M. Perkins, David A. Rahn, Camilo Rey-Sanchez, Joseph A. Santanello, Russell L. Scott, Bijan Seyednasrollah, Paul C. Stoy, Ryan C. Sullivan, Jordi Vila-Guerau de Arellano, Sonia Wharton, Chuixiang Yi, Andrew D. Richardson
Summary: This review explores how continuous, automated observations of the atmospheric boundary layer can enhance the scientific value of co-located eddy covariance measurements of land-atmosphere fluxes, with four key opportunities highlighted for integrating tower-based flux measurements with continuous atmospheric boundary layer measurements.
AGRICULTURAL AND FOREST METEOROLOGY
(2021)
Article
Construction & Building Technology
Hyunmin Yeo, Sang Lee
Summary: This study numerically investigated the turbulent wakes and recirculatory flow induced by building arrays under an atmospheric boundary layer flow to examine the influence of building arrangement on urban air mobility service. Large-eddy simulation and immersed boundary method were used to realistically mimic the atmospheric flow and the presence of building arrays. Four cases were studied, including an array of three high-rise buildings and three other combinations of high-rise and low-rise building arrays. Results showed the presence of horseshoe vortex and recirculation flows in all building configurations, with intensity varying based on the height of the upstream building. The dominant clockwise-rotating vortex was found in the cavity between the buildings. Moreover, the lateral vortex generated by the side walls of the nonuniform array tilted outward due to the secondary flow formed by the wake of the building, contributing to the downwash flow behind the building array. Elevated velocity fluctuations were observed on top of and behind the high-rise buildings, persisting downstream in parallel with the freestream flow. The largest velocity standard deviation was found to be 3.8 times that of the inflow, resulting from the combination of flow recirculation and wake from the upstream building. Velocity spectra analysis provided reference data for the deployment of vertiports and UAM take-off and landing guidance.
BUILDING AND ENVIRONMENT
(2023)
Article
Engineering, Mechanical
Vahid Mazidi Sharafabadi, Mani Fathali
Summary: This study predicts four different subgrid-scale (SGS) models in large eddy simulation (LES) of large wind farms. The impact of these models on the large wind farm simulation is evaluated by studying various parameters such as mean flow velocity, wake characteristics, wind turbine power extraction, and mean kinetic energy budget terms. The results show that different models lead to different power extraction and discrepancies in the mean kinetic energy budget terms, particularly the dissipation term between the Smagorinsky and dynamic models.
JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY
(2023)
Article
Mechanics
Mohamed Arif Mohamed, David Wood, Bing Feng Ng
Summary: In this study, an activated curvature production term was considered to describe turbulent flow over two-dimensional hills. The new term, referred to as the SR modification, depends on the difference between strain rate and rotation. It was compared to different turbulence models, and the Kato-Launder model showed the best overall predictions for various flow properties. The SR model was slightly less accurate but uniquely predicted flow separation and re-attachment in specific locations.
Article
Geosciences, Multidisciplinary
Xin Li, Zhaoxia Pu
Summary: The study found a linear relationship between the maximum intensity of large eddies and the square of mean horizontal divergence, and using this relationship in the PBL parameterization scheme can improve the accuracy of hurricane forecasts.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geosciences, Multidisciplinary
Olivia E. Clifton, Edward G. Patton, Mary Barth, John Orlando, Siyuan Wang, Colleen Baublitz
Summary: The oxidation of reactive carbon fuels has significant impacts on climate and pollution-related chemistry. Deciduous forests, especially through isoprene emissions, are important sources of reactive carbon. Turbulence can physically segregate oxidants from reactive carbon, resulting in changes in oxidation under non-well-mixed conditions. Using simulation models, these researchers quantify the impact of segregating reactive carbon from hydroxyl radicals (OH) near-canopy, finding that segregation can alter OH reactivity by up to 9%, depending on various factors. There may be discrepancies between direct measurements and estimates of OH reactivity due to segregation, separate from any issues with mischaracterized or unknown OH sinks.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Mechanics
Majid Bastankhah, Carl R. Shapiro, Sina Shamsoddin, Dennice F. Gayme, Charles Meneveau
Summary: Motivated by the need to mitigate power reduction and unsteady loading of downstream turbines, this study develops an analytical model to predict the shape of curled wakes. By estimating the vorticity distribution at the wake edge and considering the wake as a vortex sheet, the model describes the time evolution of the wake shape. The model is validated against simulations and experiments, and shows a universal solution for curled wakes with suitable dimensionless variables.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Mitchell Fowler, Tamer A. Zaki, Charles Meneveau
Summary: A large eddy simulation wall model is developed based on a formal interpretation of quasi-equilibrium that governs momentum balance. The model includes a relaxation time scale that ensures self-consistency with assumed quasi-equilibrium conditions. The new approach allows for formally distinguishing between quasi-equilibrium and additional, non-equilibrium contributions to wall stress.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Kristofer M. Womack, Ralph J. Volino, Charles Meneveau, Michael P. Schultz
Summary: This study conducted experiments on flows with regular and random roughness elements and found that there were minor differences in flow statistics between the regular and random arrangements at the same density. The observed differences in surface flow parameters were mainly due to the presence of secondary flows. Contrary to expectations, these secondary flows were present over the random surfaces and not discernible over the regular surfaces. Additionally, the local turbulent boundary layer profiles did not scale with local wall shear stress but appeared to scale with local turbulent shear stress above the roughness canopy.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
A. K. Aiyer, C. Meneveau
Summary: In this study, the dispersion characteristics of slightly buoyant droplets in a turbulent jet were investigated using large eddy simulations (LES). The model accurately captured the differential, size-based dispersion characteristics of the droplets with finer grid resolutions. Moreover, similarity solution and subgrid-scale models were used to predict the concentration profiles and turbulent concentration flux of the droplets, and the results showed good agreement with experimental data and high-resolution LES simulations.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Yuan Luo, Yipeng Shi, Charles Meneveau
Summary: The study demonstrates that equivalent predictions can be obtained by recursively modulating model terms at a single level instead of integrating the stochastic model at multiple levels and scales. The statistical properties of the model compare well with direct numerical simulation and experimental data.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Wen Wu, Charles Meneveau, Rajat Mittal, Alberto Padovan, Clarence W. Rowley, Louis Cattafesta
Summary: The response of a turbulent separation bubble to zero-net-mass-flux actuation is investigated via direct numerical simulations. The results demonstrate that the length of the separation bubble can be reduced by forming vortex pairs at the appropriate excitation frequencies. In addition, the time-averaged structures exhibit a high sensitivity to the actuation.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Mostafa Aghaei-Jouybari, Jung -Hee Seo, Junlin Yuan, Rajat Mittal, Charles Meneveau
Summary: The force partitioning method is used to analyze the pressure-induced drag for turbulent flow over rough walls. The study quantifies the contributions of rotation-dominated vortical regions and strain-dominated regions to the pressure drag, and investigates the effects of surface geometry on drag. The results suggest that the phi field, which encodes surface geometry, can be used to parametrize the surface drag.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Samvit Kumar, Charles Meneveau, Gregory Eyink
Summary: A model for the structure function tensor was proposed, incorporating the effect of anisotropy as a linear perturbation to the standard isotropic form. The analysis extends the spectral approach proposed by Ishihara et al., and valid in the inertial range of turbulence. Observations were made regarding the countergradient correlation between Fourier modes of wall-normal and streamwise velocity components near the Kolmogorov scale.
PHYSICAL REVIEW FLUIDS
(2022)
Editorial Material
Mechanics
Charles Meneveau, Colm-Cille P. Caulfield
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Ghanesh Narasimhan, Dennice F. Gayme, Charles Meneveau
Summary: Large eddy simulations are used to study the effects of veer on wind turbine wakes in the atmospheric boundary layer. The study finds that veer causes sideways wake deformation, but this can be predicted using a simple correction.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Multidisciplinary
Yinghe Qi, Charles Meneveau, Greg A. Voth, Rui Ni
Summary: Fluid elements in turbulence deform through stretching and folding. The dynamics of folding are depicted by projecting the material deformation tensor onto the largest stretching direction and tracking the evolution of material curvature. Direct numerical simulations reveal that curvature growth exhibits two stages: a linear stage dominated by folding of fluid elements through persistent velocity Hessian, followed by an exponential-growth stage driven by stretching of already strongly bent fluid elements. This transition leads to strong curvature intermittency, which can be explained by a proposed curvature-evolution model. The link between velocity Hessian and folding provides a new understanding of the energy cascade and mixing in turbulence beyond the traditional linear stretching dynamics.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Fluids & Plasmas
Ruifeng Hu, Perry L. Johnson, Charles Meneveau
Summary: This paper introduces a generalized dynamic resuspension model for particles rolling on a surface with fractal-like multiscale roughness elements, called the multiscale asperity model (MSAM). Non-Gaussian stochastic models are compared with a Gaussian stochastic model for the flow velocity seen by a particle. The results show that the non-Gaussian stochastic flow models improve the prediction of the fraction of particles remaining on the wall after a given exposure time to turbulent flow.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Mechanics
Hanxun Yao, Tamer A. Zaki, Charles Meneveau
Summary: Based on the generalized local Kolmogorov-Hill equation, this study examines the definition of entropy and entropy generation for turbulence. The results from direct numerical simulations confirm the validity of the fluctuation relation in non-equilibrium thermodynamics for turbulent flows in the inertial range.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Environmental Sciences
James C. McWilliams, Charles Meneveau, Edward G. Patton, Peter P. Sullivan
Summary: Recent high-resolution large-eddy simulations of a stable atmospheric boundary layer are analyzed and compared with observations. The simulations are judged to be converged based on the collapse of vertical profiles of winds, temperature, and turbulence moments. The subfilter-scale motions extracted from the simulations are in good agreement with observations. The data from the simulations will be made available to the research community.
Article
Mechanics
Mitchell Fowler, Tamer A. Zaki, Charles Meneveau
Summary: The recent LaRTE approach is a wall model for large-eddy simulations (LES) that separates equilibrium and non-equilibrium wall-stress dynamics. The model shows good agreement with various non-equilibrium channel flows and provides insights into wall-stress physics.
JOURNAL OF FLUID MECHANICS
(2023)
