Article
Mechanics
Xiaoning Wang, Jianchun Wang, Shiyi Chen
Summary: This study investigates the effects of compressibility on the statistics and coherent structures of a temporally developing mixing layer through numerical simulations. The results show that as the convective Mach number increases, the streamwise dissipation becomes more effective in suppressing turbulent kinetic energy. At low convective Mach numbers, the mixing layer is accompanied by spanwise Kelvin-Helmholtz rollers, while at higher convective Mach numbers, large-scale high- and low-speed structures dominate. The study also reveals a correlation between high-shearing motions on top of low-speed structures and the clustering of small-scale vortical structures.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Green & Sustainable Science & Technology
Manish Mall, K. S. Hari Prasad, C. S. P. Ojha
Summary: This study investigates and compares the scour and flow features around two different types of groynes to provide insights into their performance and efficiency in river reaches. The results indicate that the T-head groyne has a greater maximum equilibrium scour depth compared to the unsubmerged I-head groyne. Cost-benefit analysis shows that the I-head groyne is more cost-efficient in terms of bank protection lengths.
Article
Astronomy & Astrophysics
Brent Tan, S. Peng Oh, Max Gronke
Summary: Radiative mixing layers arise from the presence of multiphase gas, shear, and radiative cooling. Thermal advection from the hot phase balances radiative cooling in steady state, but many features remain puzzling, such as the characteristic velocity and scaling of hot gas heat flux. By exploiting parallels with turbulent combustion, a deeper physical understanding of radiative fronts can be achieved, shedding light on the structure and survival of cold gas in various scenarios.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Yanhui Yang, Suoqing Ji
Summary: Radiative turbulent mixing layers (TMLs) are commonly seen in astrophysical environments. High Mach number TMLs have a two-zone structure, with a mixing zone and a turbulent zone. Low Mach number TMLs do not have distinguishable zones. The cooling in high Mach number TMLs is balanced by turbulent dissipation, while in low Mach number TMLs it is balanced by enthalpy consumption.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Mechanics
Aurelien Vadrot, Alexis Giauque, Christophe Corre
Summary: This study investigates the effects of a BZT dense gas on the development of turbulent compressible mixing layers at different convective Mach numbers. Results show significant differences in momentum thickness growth rate and temperature variations between perfect gas and dense gas flows, with dense gas also affecting small scale dynamics. However, BZT effects themselves have a small impact on the mixing layer growth.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Geosciences, Multidisciplinary
Jeffrey E. Larimer, Elowyn M. Yager, Brian J. Yanites, Alex J. C. Witsil
Summary: This study conducted flume experiments to investigate the dependence of saltating gravel impact dynamics on transport stage and bed topography. The findings suggest that nonplanar bed has a more complex distribution of impact energy with a greater number of rare highly erosive impacts. Probabilistic formulations of particle trajectories better predict changes in erosion rate across experiments than deterministic regression equations.
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
(2021)
Article
Environmental Sciences
Jianqiang Xu, Yang Xue, Senjun Huang, Liyuan Zhang, Faxing Zhang
Summary: This study investigates the influence of different types of groins on flow field and river evolution, and finds that vegetation can reduce erosion. The hydrodynamic characteristics in mobile-bed experiments differ from those in fixed-bed experiments, and the improved three-dimensional groin group performs better in sediment scouring capacity and scour depth.
Article
Mechanics
Sebastien Proust, Celine Berni, Vladimir Nikora
Summary: The characteristics of shallow mixing layers behind a splitter plate were studied, focusing on the key parameters controlling the time-averaged SMLs and the formation and spatial development of Kelvin-Helmholtz coherent structures and large- and very-large-scale motions. The study found that the time-averaged flow features of the SMLs are mainly influenced by the bed-friction length scale and shear parameter, while the emergence and length scales of KHCSs depend on the value of lambda. Additionally, the presence and streamwise development of LSMs and VLSMs are affected by the lambda-value.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Geology
Xuxu Wu, Paul A. Carling, Daniel Parsons
Summary: The origins of hummocky cross-stratification and its associated bedforms and hydrodynamic processes remain controversial. In a large-scale flume experiment, it was found for the first time that waves perpendicular to a current can generate hummock-like structures in conjunction with ripples. The length of these structures under combined flow can reach approximately 40 mm and is related to enhanced turbulence.
Article
Environmental Sciences
Liliya Khatmullina, Irina Chubarenko Shirshov
Summary: Synthetic fibers of several tens of micrometers in diameter are the most common microplastics in the marine environment, but their dynamics in the water column are still poorly understood. Experimental results demonstrate significant changes in sinking velocity and behavior of fibers in still water and thermal convection conditions.
ENVIRONMENTAL POLLUTION
(2021)
Article
Mechanics
Yuping Bai, Peiwen Yan, Quanbin Zhao, Daotong Chong, Yifei Yu, Zhihui Zhang, Junjie Yan
Summary: The origin and relationship between initial streamwise vortices in braid regions and deformed spanwise vortices are studied using direct numerical simulation (DNS) in a compressible mixing layer. Through analysis of DNS data using fast Fourier transform, two low-rank velocity models (v(d) and v(s)) are developed to show that both deformed spanwise vortices and streamwise vortices originate from the linear superposition of several modes. Further investigations reveal that the increase in amplitude ratio between modes leads to the formation of deformed spanwise vortices in vortex regions and the generation of streamwise vortices in braid regions.
Review
Multidisciplinary Sciences
Lucas Madeira, Vanderlei S. Bagnato
Summary: This paper reviews the recent advances in observing non-thermal fixed points (NTFPs) in experiments involving Bose gases. It provides a brief introduction to the theory behind NTFP universality classes and focuses on experimental observations of NTFPs. The benefits of NTFP universality classes are presented by analogy with renormalization group theory in equilibrium critical phenomena.
Article
Physics, Fluids & Plasmas
Brandon E. Morgan
Summary: This study involves large-eddy simulations of a Kelvin-Helmholtz mixing layer, showing similarities in scalar variance integral behavior with a Rayleigh-Taylor mixing layer and a tendency towards mixedness of about 0.8 in the simulated KH shear layer. It is found that using a Reynolds-averaged Navier-Stokes model calibrated for an RT layer to simulate a KH layer results in significant overprediction of scalar variance, suggesting the addition of a buoyancy production term to match mixedness in simulations of both RT and KH layers with a single model calibration.
Article
Geosciences, Multidisciplinary
Lixin Qu, Leif Thomas, Jonathan Gula
Summary: The study found that storm-generated near-inertial waves (NIWs) were observed on the seafloor of the Straits of Florida, and numerical simulations provided evidence that these waves can enhance mixing in the seafloor of the straits. This mixing could potentially influence benthic deep-water coral ecosystems and properties of intermediate water masses.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Mechanics
Syed Mohammad Ovais, Konstantin A. Kemenov, Richard S. Miller
Summary: Direct numerical simulations were conducted on temporally developing, three-dimensional mixing layers of CH4/CO2, CH4/O-2, and CO2/O-2 at a supercritical pressure of 300atm. The employed formulation included compressible governing equations, the Peng-Robinson equation of state, and a generalized formulation for heat and mass flux vectors. Flow visualizations revealed high density gradient magnitude regions and increased presence of heavier fluid species within these regions. No significant departures from perfect gas behavior were observed.
