Article
Thermodynamics
Aritra Roy Choudhury, Kameswararao Anupindi
Summary: In this study, a planar turbulent offset wall-jet with heat transfer is numerically investigated using large-eddy simulation (LES). The flow characteristics, thermal characteristics, and turbulent kinetic energy of the jet are analyzed. The evolution of Nusselt number on the wall exhibits three distinct peaks correlated with the change-of-sign of the wall skin-friction coefficient. The flow domain can be categorized into recirculation, impingement, and wall-jet regions, and distinct flow and thermal characteristics are observed in different regions.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Engineering, Multidisciplinary
Sayahnya Roy, Krishnendu Barman, Koustuv Debnath, Bijoy S. Mazumder
Summary: The study found that the axial jet velocity decays faster in counter turbulence, leading to a reduced entrainment rate of the moving fluid. Eddy intermittency and diffusion depth decreased for jets issued against the current. The kinetic energy budget analysis showed that the pressure diffusion term supplied energy to the jet from the mean background flow.
Article
Engineering, Aerospace
Alexey P. Duben, Jesus Ruano, Andrey V. Gorobets, Joaquim Rigola, F. Xavier Trias
Summary: An investigation of various eddy viscosity models for accurate scale-resolving simulation of aerodynamics and aeroacoustics of a turbulent jet is presented. The study demonstrates the importance of both a numerical scheme and a subgrid turbulence model for accurate prediction of noise generated by a turbulent jet.
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
Mechanics
T. H. New, G. J. Gotama, U. S. Vevek
Summary: The study conducted numerical simulations on head-on collisions between vortex-rings and round cylinders, revealing vortical behavior and flow details not previously observed. Results showed that smaller diameter-ratio cylinders can produce elliptic vortex-ringlets with increased aspect ratio and axis-switching behavior. Additionally, tertiary vortex-ring cores were formed and merged within the confines of primary vortex-ring cores, leading to the formation of inner vortex-dipoles.
Article
Computer Science, Interdisciplinary Applications
A. C. W. Creech, A. Jackson
Summary: This paper introduces a hybrid approach for explicitly-filtered Large Eddy Simulation using a Discontinous Galerkin discretisation for velocity, which incorporates information from a Continuous Galerkin version of the velocity field to improve computational performance while maintaining stability and accuracy.
COMPUTER PHYSICS COMMUNICATIONS
(2021)
Article
Mechanics
A. Thawko, R. van Hout, H. Yadav, L. Tartakovsky
Summary: The study revealed that the development of an impulsively started round, confined nitrogen jet can be divided into two stages. In stage I, the jet is characterized by a leading toroidal vortex, while in stage II, the jet becomes moderately underexpanded and near the nozzle exit, resembling characteristics of a co-annular jet with the co-annular region not extending beyond 15 times the nozzle diameter.
Article
Mechanics
Xin Lai, Shaofan Li, Jiale Yan, Lisheng Liu, A-Man Zhang
Summary: This study investigates the dispersion of virus-laden droplets in coughing jets using large-eddy simulations. The turbulence of the jet determines the droplets' dispersion, and the droplet particles increase the complexity of the turbulence. The spreading distance of droplets often exceeds the recommended social distancing rules, highlighting the importance of protective measures.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Thermodynamics
E. Cascioli, S. Keijers, K. Van Tichelen, J. E. Vesper, S. Kenjeres
Summary: In this study, a combined dynamic large-eddy simulation (LES) and direct numerical simulation (DNS) approach was applied to analyze the flow and heat transfer characteristics of a three-dimensional planar jet in a turbulent forced convection regime. The results were compared with Reynolds Averaged Navier-Stokes (RANS) simulations and experimental data. Detailed insights into the behavior of velocity and temperature fields for four different characteristic Prandtl numbers were provided, with a focus on low-Prandtl working fluids for advanced RANS-type turbulence models development and validation.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
Parth Thaker, Somnath Ghosh
Summary: In this study, large eddy simulations of subsonic round jets were conducted using a high order compact finite difference scheme and an explicit filtering based approximate deconvolution method. The results obtained were in good agreement with existing literature, showing that the increase in co-flow velocity ratio leads to an increase in potential core length and a decrease in spreading rate of the jet, resulting in reduced turbulence intensities and near-field sound levels.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2021)
Article
Meteorology & Atmospheric Sciences
Yu Cheng, Marco G. Giometto, Pit Kauffmann, Ling Lin, Chen Cao, Cody Zupnick, Harold Li, Qi Li, Yu Huang, Ryan Abernathey, Pierre Gentine
Summary: In large-eddy simulations, subgrid-scale processes are parameterized as a function of filtered grid-scale variables. This paper applies supervised deep neural networks (DNNs) to learn subgrid stresses and achieves higher correlation compared to traditional models, with applicability to different resolutions and stability conditions.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2022)
Article
Engineering, Ocean
Chetankumar Anghan, Mukund H. Bade, Jyotirmay Banerjee
Summary: This study investigates the evolution of a round jet released in regular waves through direct numerical simulation. It is found that the vortex roll-up frequency in the wave environment is lower compared to the free jet. The counter-rotating vortex pairs in the jet under regular waves exhibit asymmetry due to the deflection of the jet. The wave tractive mechanism provides the jet with an additional opportunity to entrain fresh fluid. The preferred mode in the case of the jet in regular waves is helical, unlike the varicose mode in the free jet. The mean quantities and turbulence levels in the jet under regular waves are significantly higher than in the free jet.
APPLIED OCEAN RESEARCH
(2022)
Article
Automation & Control Systems
Xiaotong Ren, Shengqiang Shen, Yong Yang, Hui Lv, Yali Guo
Summary: In this research, numerical simulations of a turbulent round jet were performed using large eddy simulation (LES) and the results were compared to Reynolds-averaged Navier-Stokes (RANS). The turbulence statistics are independent of the Reynolds number for Re >= 1104. A three-dimensional turbulent round jet near the exit, with a Reynolds number of 6.2104, was simulated to better represent real-world engineering applications. The comparison of LES and RANS turbulence models with experimental data showed that LES provides more accurate predictions of the core area and length of the jet core, and its turbulence statistics agree with experimental results.
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
(2023)
Article
Mechanics
Taye Melaku Taddesse, Joseph Mathew
Summary: This study investigates the velocity field characteristics of stationary, turbulent twin round jets. Large-eddy simulations were conducted to obtain the flow fields, revealing that the two jets develop independently and merge into a single jet with an elliptic cross-section downstream. The merged jet becomes circular after a certain distance. The fluctuation levels of the merged jet scale with the local maximum mean velocity, and the mean streamwise velocity reaches a peak at a certain distance from the inflow plane. The velocity and length scales of the merged jet are connected to the input parameters through simple relations, and the far field development can be scaled using intrinsic scales.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Aerospace
Yue Yang, Junkui Mao, Feilong Wang, Xingsi Han
Summary: In this study, a high-resolution simulation was conducted to investigate the unsteady turbulent convection of jet impingement under vibration conditions. It was found that the introduction of vibration promoted the development of primary vortices and had an impact on the heat transfer performance.
CHINESE JOURNAL OF AERONAUTICS
(2022)
Article
Engineering, Aerospace
Christophe Bogey
Summary: The study investigates the generation of noise by jets with highly disturbed laminar boundary-layer profiles at the nozzle exit. Jets with laminar boundary-layer profiles radiate greater sound pressure levels than the jet with a nonlaminar profile, but with weaker initial disturbances. The results demonstrate the dependence on the shape of the boundary-layer profile of the most unstable frequencies downstream of the nozzle.
Article
Engineering, Aerospace
Pierre Pineau, Christophe Bogey
Summary: The relationship between coherent structures in the shear layer of an isothermal Mach 2 jet and steepened Mach waves just outside the jet has been investigated through large-eddy simulation. The steepened aspect of the waves increases with their intensity, and is not likely due to nonlinear propagation effects. The properties of the waves vary with convection speed, strength, and geometrical shape of the mixing layer structures, with intensity and steepened aspect increasing due to stronger and more inclined shear-layer structures.
Article
Acoustics
Pierre Pineau, Christophe Bogey
Summary: The study investigates wave steepening and shock coalescence due to nonlinear propagation effects in a cold Mach 3 jet. The results show that the positive asymmetry of pressure fluctuations originates during the wave generation process, rather than being caused by nonlinear propagation effects.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2021)
Article
Mechanics
R. Camussi, C. Bogey
Summary: This paper investigates the statistical properties of pressure fluctuations in the near field of subsonic compressible jets. Through numerical analysis of two single-stream circular jets, it is shown that intermittent behavior is relevant even at low Reynolds numbers for the full signals, while apparently not significant for the 0-mode component. Wavelet analysis reveals relevant intermittency around frequencies associated with the Kelvin-Helmholtz instability in the 0-mode component.
THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS
(2021)
Article
Mechanics
Christophe Bogey
Summary: This study investigates the acoustic characteristics of jet nozzles for Mach numbers between 0.50 and 2 using large-eddy simulations. Peaks are observed near the nozzles, with tonal qualities at higher Mach numbers and broader qualities at lower Mach numbers. The frequencies of these peaks are related to azimuthal modes and remain consistent with the predicted frequency bands for upstream-propagating guided jet waves.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Nanoscience & Nanotechnology
P. Pineau, C. Bogey
Summary: The study investigates the effects of jet interactions and acoustic shielding on the noise of strongly heated supersonic twin jets through large-eddy simulations. It reveals that jet interactions can weaken some sound sources, leading to an overall reduction in acoustic power. Despite the noise reduction, some noise components are stronger for twin jets, indicating the generation of additional interaction noise.
Article
Engineering, Aerospace
Christophe Bogey
Summary: The study investigated the presence of tones in the acoustic far field of isothermal round jets for different angles, revealing peaks in the far-field pressure spectra for all Mach numbers. The characteristics of these peaks varied with the radiation angle, with more prominent peaks associated with lower azimuthal modes as the angle increased.
Article
Engineering, Aerospace
Andres Adam, Dimitri Papamoschou, Christophe Bogey
Summary: The study investigates the turbulent scales in a Mach 0.9 isothermal round jet to develop linear surface-based noise source models informed by a Reynolds-averaged Navier-Stokes (RANS) solution. Different space-time correlations are observed for axial velocity fluctuations and pressure fluctuations, with small-scale eddies showing minimal impact on the radiator surface. Simple relationships are inferred to aid the development of rapid predictive models.
Article
Engineering, Aerospace
Gaetano Luca Micci, Roberto Camussi, Stefano Meloni, Christophe Bogey
Article
Mechanics
Mathieu Vare, Christophe Bogey
Summary: In this study, the generation of acoustic tones in four round jets at a Mach number of 0.9 impinging on a plate was investigated using large-eddy simulation. The effects of hole diameter on the jet flow and acoustic fields were studied. It was found that the levels of acoustic tones decrease with the increase of hole diameter. The features of the feedback loops were identified through space-time correlations and frequency-wavenumber spectra analysis. The results showed that the pressure fluctuations on the plate dominate the radiated noise.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Aerospace
Valentin Morin, Julien Troyes, Francois Vuillot, Christophe Bogey
Summary: This study focuses on a water injection system and conducts a large-eddy simulation of an experimental water jet. The results show that the jet mean radius and initial instability frequency are consistent with experimental data, but the jet transition position varies with fluctuation levels at the nozzle exit. When the impingement phenomenon is considered, droplets are absorbed before reaching the center.
Article
Engineering, Aerospace
Stefan Schoder, Etienne Spieser, Hugo Vincent, Christophe Bogey, Christophe Bailly
Summary: The capabilities of an aeroacoustic wave equation based on Pierce's operator (AWE-PO) for modeling subsonic flow-induced sound and sound prediction are investigated. The wave equation is applied to an isothermal two-dimensional mixing layer computed by direct numerical simulation. Comparisons between Lighthill's wave equation and AWE-PO suggest a much smaller source amplitude for AWE-PO, attributed to the filtering property of the material derivative. The results show that both wave equations accurately capture the radiated sound field's directivity, propagation, and convection effects, with comparable acoustic intensities to direct numerical simulation.
Article
Acoustics
Etienne Spieser, Christophe Bogey, Christophe Bailly
Summary: The study investigates the turbulent mixing noise generated by a Mach 0.9 jet and focuses on accurately calculating the acoustic propagation effects using adjoint Green's function tailored to the jet mean flow. Tam and Auriault's statistical mixing noise model is modified for Pierce's wave equation to ensure energy preservation. A stable formulation for computing propagation effects is obtained, and adjoint fields are computed using the flow reversal theorem. The study demonstrates how tailored adjoint Green's functions filter the radiating part of Tam and Auriault's sound source model by weighting with propagation effects.
JOURNAL OF SOUND AND VIBRATION
(2023)
Article
Acoustics
Courtney Ford, Antonio Pereira, Christophe Bailly
Summary: This work aims to predict the transfer function of a given modal content inside a circular duct with a bellmouth inlet in the presence of a mean flow. The transfer function represents the relation between amplitude and phase of a given mode inside the duct and an observer located in the far-field. A numerical solution is obtained through finite element simulation with the mean flow as input data. Verification is done by comparing with the analytical solution of an unbaffled circular duct with uniform flow. The study investigates the influence of various parameters such as geometry and mean Mach number on the radiated pressure field. The analytical solution serves as a good approximation for determining the radiated principal lobe, and the inlet geometry is found to be more significant than other parameters when studying static inlet configuration.
Article
Acoustics
Simon L. Prigent, Christophe Bailly
Summary: This study presents a semi-analytical method to compute the wall pressure spectra beneath a turbulent boundary layer using the Karman number and dimensionless pressure gradient. By incorporating mean shear profiles into a mixing length model, the velocity profiles can be reconstructed under different pressure gradients. The modelled frequency spectra closely estimate the measured ones and the effects of pressure gradients on the convective ridge structure are observed.