Article
Mechanics
Jorge S. Salinas, S. Balachandar, Santiago L. Zuniga, M. Shringarpure, J. Fedele, D. Hoyal, M. Cantero
Summary: Gravity currents are studied in this work, focusing on the flow of a heavier fluid along the bottom of a sloping bed, beneath a stagnant lighter ambient fluid. The thickness of the current increases due to entrainment of ambient fluid. The rate of penetration of mean momentum, mean concentration, and turbulence-related quantities into the ambient fluid are analyzed, with a comparison to wall-bounded turbulent flows.
Article
Multidisciplinary Sciences
Rajesh K. Mahato, Sk Zeeshan Ali, Subhasish Dey
Summary: We investigate the growth rate, resonant wavenumber, and phase velocity of longitudinal sediment waves generated by the interaction of turbidity currents with an erodible bed through linear and weakly nonlinear stability analyses. The study reveals the influence of key parameters on these quantities and the migration of sediment waves. A stability diagram accurately captures experimental data within the unstable zone. The weakly nonlinear analysis provides the equilibrium amplitude of sediment waves and its sensitivity to key parameters, with results comparable to field observations.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2023)
Review
Mechanics
Thomas Peacock, Raphael Ouillon
Summary: The evolution and fate of sediment plumes in the deep sea mining industry are determined by transport processes, which require more fundamental and applied fluid mechanics research for accurate prediction. Efforts combining theory, modeling, experiments, and trials have made progress in assessing the role of parameters in setting the extent of plumes, but there are currently no established best practices for the design and operation of mining technologies.
ANNUAL REVIEW OF FLUID MECHANICS
(2023)
Article
Geography, Physical
Huazhen Huang, Zhifei Liu, Yulong Zhao, Hongchao Zhao, Adrian R. Fernandez, Christophe Colin, Andrew Tien-Shun Lin
Summary: This study investigates the clay mineral assemblage of late Holocene turbidites in the Gaoping Submarine Canyon to reveal the triggering mechanisms of turbidity currents. The results show that the Gaoping river is the predominant source of sediments in the turbidite layers, while the hemipelagite layers receive sediments from other nearby rivers in southwest Taiwan. It is believed that the turbidity currents, triggered mainly by typhoons passing through Taiwan, directly supplied clay minerals to the submarine canyon to form the turbidites.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
(2023)
Article
Mechanics
Hua Zhou, Evatt R. Hawkes, Timothy C. W. Lau, Rey Chin, Graham J. Nathan, Haiou Wang
Summary: Point-particle direct numerical simulations were used to quantify the turbulence modulation and particle responses in a turbulent particle-laden jet in the two-way coupled regime. The results showed that the presence of particles both reduced and increased the gas-phase turbulent kinetic energy in different regions. The particle response to the gas-phase flow was found to be stronger in the axial velocity component.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Oceanography
S. Haddadian, C. E. Ozdemir, B. L. Goodlow, G. Xue, S. J. Bentley
Summary: This study investigates the velocity structure of ACSTCs through direct numerical simulations and provides parameterization relations. The results show that density stratification and drag coefficient are influenced by the product of sediment settling velocity and sediment concentration, affecting the amount of sediments carried by ACSTCs. The role of sediment-induced stable density stratification is analyzed to determine the velocity profile of ACSTCs.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2021)
Article
Mechanics
Jiasheng Yang, Alexander Stroh, Daniel Chung, Pourya Forooghi
Summary: Direct numerical simulations (DNS) are used to predict the accuracy of roughness function and zero-plane displacement in properly sized minimal channels. The predictions remain accurate even when the domain size is reduced and 90% of the roughness height variance is retained. The roughness function is nearly unique for deterministic different surface topographies. The distribution of surface force exerted by the roughness can be well captured when considering the sheltering effect.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Francisco Alcantara-Avila, Sergio Hoyas, Maria Jezabel Perez-Quiles
Summary: A direct numerical simulation of turbulent heat transfer in a channel flow was conducted at a Reynolds number of and a Prandtl number of air, . The study obtained mean values and intensities of temperature, calculated parameters such as the von Karman constant and the Nusselt number, and proposed correlations. It was observed that an asymptotic behavior of the von Karman constant was present as the Reynolds number increased.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Mateus C. Guimaraes, Fernando T. Pinho, Carlos B. da Silva
Summary: This study employs the FENE-P model to conduct direct numerical simulations and investigate the far-field region of turbulent wakes of viscoelastic fluids. The results show new scaling laws for various parameters and are well supported by the numerical simulations. When the Weissenberg and Deborah numbers are sufficiently large, turbulent viscoelastic wakes exhibit distinctive behavior compared to Newtonian wakes.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Jean-Mathieu Teissier, Wolf-Christian Mueller
Summary: Through Fourier shell-to-shell transfer analysis, the role of different helical components of magnetic and velocity fields in the inverse spectral transfer of magnetic helicity was investigated. Three physical phenomena were distinguished in the spectral transfer of magnetic helicity: local inverse transfer, non-local inverse transfer, and local direct transfer.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Jean-Mathieu Teissier, Wolf-Christian Mueller
Summary: This study investigates the inverse transfer of magnetic helicity in large-scale mechanically driven turbulent flows using direct numerical simulations in the ideal magnetohydrodynamics framework. It is found that compressibility leads to smaller absolute values of magnetic helicity scaling exponents, and strong deviations are visible in compressively driven turbulence even at relatively low Mach numbers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
J. Pratt, A. Busse, W-C Mueller
Summary: This study investigates the influence of a magnetic field on anisotropic magnetohydrodynamic (MHD) turbulence using direct numerical simulations. The results show that the diffusion curves of single particles exhibit mildly superdiffusive behaviors in different directions. The dispersion of particle pairs is affected by competing alignment processes, especially at the beginning of the inertial subrange. The observed scaling for relative dispersion is steeper than the Richardson prediction, particularly at larger Reynolds numbers.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Jie Yao, Fazle Hussain
Summary: Compressible turbulent plane Couette flows with high Reynolds and Mach numbers were studied through direct numerical simulation. Various turbulence statistics were compared with incompressible flows. The skin friction coefficient decreases with Reynolds number but weakly depends on Mach number. The thermodynamic properties show significant variations with Mach number. Proper scaling transformations collapse the mean velocity profiles for compressible and incompressible cases well. Semilocal units yield a better collapse for Reynolds stress profiles compared to wall units. The length scale of near-wall coherent structures and the strength of the superstructures increase with Reynolds number. The streamwise coherence of the superstructures degrades with increasing Mach number.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Water Resources
X. -Q. Tang, C. G. Koh, M. Luo
Summary: This paper extends the Consistent Particle Method (CPM) to simulate turbidity currents and focuses on turbulent water-sediment flow. With a mixture model and CPM-upwind scheme, the sediment mass transfer and suspended sediment diffusion can be accurately simulated. Validation and application examples demonstrate the feasibility and accuracy of CPM in simulating water-sediment flow.
ADVANCES IN WATER RESOURCES
(2023)
Article
Engineering, Multidisciplinary
Jin Xu, Jihong Xia, Lingling Wang, Eldad J. Avital, Hai Zhu, Yin Wang
Summary: An improved Eulerian method with a novel morphologic model is developed to study local scour. The method accurately captures the local scour and agrees with experimental results. The results also highlight the importance of Reynolds stress in erosion at the leading edge of the cylinder.
APPLIED MATHEMATICAL MODELLING
(2022)
Article
Mechanics
Jorge S. Salinas, Santiago Zuniga, M. Cantero, M. Shringarpure, J. Fedele, D. Hoyal, S. Balachandar
Summary: This study investigates gravity currents in the subcritical to supercritical range through seven direct and large-eddy simulations. The focus is on the near-self-similar state reached by the currents downstream, where certain factors reach a constant value while others continue to increase linearly. The study also examines their dependence on the slope.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
J. St Clair, T. McGrath, S. Balachandar
Summary: This study describes particle-resolved simulations of a single aluminum particle interacting with a strong nitromethane shock within a layer of particles. The results show that the presence of neighboring particles influences the shape, plastic deformation, and strength of shock reflection of the particles.
Article
Thermodynamics
Sudhanshu Pandey, Sang Youl Yoon, S. Balachandar, Man Yeong Ha
Summary: The thermal and flow characteristics of carboxymethyl cellulose (CMC) were studied using experimental and numerical methods to assess shear-thinning behavior in a non-Newtonian fluid. A novel particle image velocimetry technique was utilized to analyze natural convective flow. The Carreau model was found to be the most effective in predicting the thermal and flow performance within the studied thermal system.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Environmental Sciences
Minglan Yu, Xiao Yu, S. Balachandar
Summary: A two-phase Euler-Lagrangian framework was used to study the flocculation dynamics of cohesive sediment in isotropic turbulence. The research found that the ratio of turbulent shear to floc strength strongly influenced the floc size distribution and settling velocity.
WATER RESOURCES RESEARCH
(2022)
Article
Physics, Fluids & Plasmas
Jacob Behrendt, S. Balachandar, T. P. McGrath
Summary: This paper investigates shock propagation over randomly distributed beds using particle-resolved simulations and quantifies the force on individual particles. It is found that while the average force coefficient is similar to that of isolated particles, the force experienced by individual particles varies substantially. Additionally, the specific locations of neighboring particles upstream and downstream result in persistent forces on particles.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
Santiago L. Zuniga, Jorge S. Salinas, S. Balachandar, Mariano Cantero
Summary: Six highly resolved direct and large eddy simulations of gravity and conservative turbidity currents are presented to illustrate the universal cyclic sequence of four states that these currents follow in their rapidly varying evolution. The demarcation between these states is determined by the bulk Richardson number and the acceleration/deceleration of the flow. The identification process and the associated three-dimensional structure of the current are described in detail. The exact depth-averaged momentum balance is computed to explain the intricate details of the nonmonotonic rapid evolution of the current between the different states. The balance of turbulent kinetic energy and concentration flux are also computed to explain the mechanism by which the current can exit the cyclic sequence and slowly evolve towards self-similar supercritical or subcritical states.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Computer Science, Interdisciplinary Applications
M. Allahyari, K. Liu, J. Salinas, N. Zgheib, S. Balachandar
Summary: Using large eddy simulations, the dynamic behavior of puffs and droplets generated by coughs and sneezes was investigated. The effects of ejection volume, momentum, orientation, and mouth shape on the dynamics were explored. It was found that the ejection angle and mouth shape have minimal impact on the puff and droplet dynamics.
COMPUTERS & FLUIDS
(2023)
Article
Mechanics
S. Balachandar, Kai Liu
Summary: This study improves upon prior correction procedures for particle self-induced perturbation velocity in a two-way coupled Euler-Lagrange simulation. It introduces a vector correction procedure that allows for different directions of feedback force and relative velocity, and incorporates the effect of a nearby wall. Analytical and numerical methods are presented for obtaining the regularization Oseen solutions necessary for the correction procedure. The study demonstrates the rapid convergence of the correction procedure within three or four iterations.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Mechanics
K. A. Krishnaprasad, J. S. Salinas, N. Zgheib, S. Balachandar
Summary: We propose a statistical framework to estimate airborne droplet nuclei concentration in indoor spaces by accounting for the effects of recycling and filtration in ventilation systems. The framework is demonstrated in a typical room with a four-way cassette air-conditioning system, where the flow field is computed using large eddy simulations. Our approach breaks down the path of virus-laden droplet nuclei into four separate processes, enabling us to provide turbulence-informed and statistically relevant pathogen concentration at any location in the room. The analysis shows that proper filtration can significantly increase the cumulative exposure time and allow longer visitations in nursing homes.
Article
Mechanics
Sam Briney, S. Balachandar
Summary: Supersonic aircraft flying in bad weather can be damaged by impacts from water droplets and other airborne particles. The particles encounter a bow shock before impact, causing them to break up into smaller droplets. These smaller droplets are less likely to collide with the aircraft due to their reduced inertia.
Article
Mechanics
Jorge S. Salinas, S. Balachandar, Santiago L. Zuniga, M. Shringarpure, J. Fedele, D. Hoyal, M. Cantero
Summary: Gravity currents are studied in this work, focusing on the flow of a heavier fluid along the bottom of a sloping bed, beneath a stagnant lighter ambient fluid. The thickness of the current increases due to entrainment of ambient fluid. The rate of penetration of mean momentum, mean concentration, and turbulence-related quantities into the ambient fluid are analyzed, with a comparison to wall-bounded turbulent flows.
Article
Multidisciplinary Sciences
Minglan Yu, Xiao Yu, Ashish J. Mehta, Andrew J. Manning, Faisal Khan, S. Balachandar
Summary: The study investigates the impact of turbulence on flocculation by analyzing the time-evolution of individual flocs within an Eulerian-Lagrangian framework. It identifies two mechanisms of floc reshaping: breakage-regrowth and restructuring by hydrodynamic drag. Surface erosion is the primary breakup mechanism for strong flocs, while fragile flocs tend to split into fragments of similar sizes. Turbulence lowers the aggregation efficiency of flocs comparable to or greater than the Kolmogorov scale. The findings emphasize the restrictive effects of turbulence on both floc size and structure.
SCIENTIFIC REPORTS
(2023)
Article
Physics, Fluids & Plasmas
B. Siddani, S. Balachandar
Summary: Developing deterministic neighborhood-informed point-particle closure models using machine learning has attracted interest in the dispersed multiphase flow community recently. However, the robustness of neural models for this complex multibody problem is hindered by the lack of particle-resolved data. In this study, two strategies are implemented to address this limitation: the use of a rotation and reflection equivariant neural network, and a physics-based hierarchical machine learning approach. The resulting machine-learned models demonstrate high accuracy in predicting neighbor-induced force and torque fluctuations under various conditions.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Computer Science, Interdisciplinary Applications
K. Choudhary, K. A. Krishnaprasad, S. Pandey, N. Zgheib, J. S. Salinas, M. Y. Ha, S. Balachandar
Summary: We investigate the dispersal of droplet nuclei in a room with a four-way cassette air-conditioning unit using RANS simulations. The simulations compare well with reference LES simulations, suggesting that the computationally cheaper RANS model can be used to predict pathogen concentration in confined spaces. However, there may be an increased statistical discrepancy.
COMPUTERS & FLUIDS
(2023)
Article
Mechanics
Andreas Nygard Osnes, Magnus Vartdal, Mehdi Khalloufi, Jesse Capecelatro, S. Balachandar
Summary: This article presents models for quasi-steady drag, quasi-steady drag variation, and transverse forces in compressible flows through random, fixed particle suspensions. The correlations are formulated based on drag force measurements obtained from particle-resolved simulation data covering a range of flow conditions from subsonic to supersonic. The newly proposed drag models extend existing models for incompressible dense gas-solid flows to finite Mach numbers, while the transverse particle force model is novel and incorporates the covariation between streamwise and transverse forces.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
