Article
Mechanics
Matthew Bross, Sven Scharnowski, Christian J. Kaehler
Summary: Studies have shown that in compressible turbulent boundary layer flows, the frequencies of superstructures have slightly longer streamwise wavelengths, and there is a distinct increase in the spanwise spacing of superstructures in supersonic cases compared to subsonic and transonic turbulent boundary layers.
JOURNAL OF FLUID MECHANICS
(2021)
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
Bajrang Sharma, Sharath S. Girimaji
Summary: The stability of compressible boundary layer flows is affected by the Mach number and Prandtl number, with increasing Prandtl number resulting in increased instability. Different perturbation modes have varying effects on stability.
JOURNAL OF FLUID MECHANICS
(2022)
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)
Article
Mechanics
Peng-Jun-Yi Zhang, Zhen-Hua Wan, Si-Wei Dong, Nan-Sheng Liu, De-Jun Sun, Xi-Yun Lu
Summary: This study presents a comprehensive analysis on the extreme events in compressible turbulent boundary layers using direct numerical simulations. The study focuses on the relationship between the extreme events and wall streaks as well as alternating positive and negative structures. A novel decomposition method is proposed to quantify the momentum and energy transport mechanisms.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Peng-Jun-Yi Zhang, Zhen-Hua Wan, Nan-Sheng Liu, De-Jun Sun, Xi-Yun Lu
Summary: This study investigates the effect of wall cooling on pressure fluctuations in compressible turbulent boundary layers using high-fidelity direct numerical simulations. Opposite effects of wall cooling on pressure fluctuations are found between subsonic/supersonic cases and the hypersonic case. Wall cooling suppresses pressure fluctuations in the former cases, while enhancing them in the latter case, especially near the wall. The main effects of wall cooling can be interpreted by the suppression of the vorticity mode and the enhancement of the acoustic mode.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Kevin P. Griffin, Lin Fu, Parviz Moin
Summary: In this work, a near-wall model is developed for high-speed turbulent boundary layers by coupling a recently developed compressible velocity transformation and an algebraic temperature-velocity relation. The model can predict mean temperature and velocity profiles, as well as wall shear stress and heat flux, using the mean flow state at specific heights. The model is significantly more accurate than the classical ordinary differential equation (ODE) model and has similar computational cost and implementation complexity.
JOURNAL OF FLUID MECHANICS
(2023)
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
Metallurgy & Metallurgical Engineering
Hana Aouinet, Maher Dhahri, Mohammad Reza Safaei, Habib Sammouda, Ali E. Anqi
Summary: A numerical analysis was conducted on the log-law behavior of the turbulent boundary layer over a flat plate immersed in three nanofluids, showing that changes in nanoparticle concentrations have an impact on velocity, temperature profiles, wall shear stress, and turbulent intensity. Additionally, the section with significant temperature changes corresponds to a decrease in thickness of the thermal boundary layer as velocity decreases.
JOURNAL OF CENTRAL SOUTH UNIVERSITY
(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
Marco Ferro, Bengt E. G. Fallenius, Jens H. M. Fransson
Summary: New experimental results demonstrate that turbulent asymptotic suction boundary layers (TASBLs) can be achieved with wall suction, showing unique characteristics independent of streamwise location. The wall suction results in a significant damping of velocity fluctuations and reduces turbulent activity.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
John Panickacheril John, Jorg Schumacher
Summary: Buoyancy-driven turbulent convection exhibits a top-down asymmetry when the adiabatic equilibrium profiles of temperature, density, and pressure change strongly across the convection layer. This asymmetry grows and leads to the formation of a thickened stabilized sublayer at the top of the convection zone. The highly stratified compressible convection regime shows a significant reduction in global turbulent heat transfer and the presence of sparse thermal plumes falling through the top sublayer.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Akanksha Baranwal, Diego A. Donzis, Rodney D. W. Bowersox
Summary: This study investigates the effects of compressibility on the near-wall asymptotic behavior of turbulent fluxes using a large direct numerical simulation (DNS) database, finding that the behavior of compressible turbulent flow near walls differs from incompressible flow even when mean density variations are considered. As Mach number increases, turbulent fluxes containing wall-normal components exhibit a decrease in slope due to increased dilatation effects, with Ity approaching its high Mach number asymptote at lower Mach numbers than other fluxes.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
R. Baidya, J. Philip, N. Hutchins, J. P. Monty, I. Marusic
Summary: The study reveals that the impact of Reynolds number on spanwise velocity generally follows a logarithmic trend, with the presence of intermediate-scale eddies leading to characteristics related to the distance from the wall.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
M. Gul, B. Ganapathisubramani
Summary: This study investigates the flow characteristics of a turbulent boundary layer over different sand-grain roughness created by different sandpapers. The results show self-similarity in flow properties within a certain range, regardless of transitional or fully rough conditions. Despite differences in turbulence profiles, large-scale structures across all locations remain independent of roughness parameters.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Matteo Bernardini, Davide Modesti, Sergio Pirozzoli
COMPUTERS & FLUIDS
(2016)
Article
Mechanics
Matteo Bernardini
JOURNAL OF FLUID MECHANICS
(2014)
Article
Mechanics
Sergio Pirozzoli, Matteo Bernardini, Paolo Orlandi
JOURNAL OF FLUID MECHANICS
(2014)
Article
Physics, Fluids & Plasmas
Pedro S. Volpiani, Matteo Bernardini, Johan Larsson
PHYSICAL REVIEW FLUIDS
(2020)
Article
Mechanics
E. Martelli, L. Saccoccio, P. P. Ciottoli, C. E. Tinney, W. J. Baars, M. Bernardini
JOURNAL OF FLUID MECHANICS
(2020)
Article
Thermodynamics
M. Cimini, E. Martelli, M. Bernardini
Summary: A calibrated delayed detached eddy simulation of a sub-scale cold-gas dual-bell nozzle flow at high Reynolds number and in sea-level mode was conducted, showing a symmetric and controlled flow separation at the inflection point in the over-expanded flow, resulting in low aerodynamic side loads. Analysis of nozzle wall-pressure signature in the frequency domain, in comparison with experimental data for the same geometry and flow conditions, indicates good agreement in the low mean value of side-loads, confirming the interaction between separation-shock and detached shear layer is dampened by the inflection point.
FLOW TURBULENCE AND COMBUSTION
(2021)
Article
Physics, Fluids & Plasmas
Francesco De Vanna, Michele Cogo, Matteo Bernardini, Francesco Picano, Ernesto Benini
Summary: The study presents a general strategy to unify wall-resolved and wall-modeled large-eddy simulation approaches for turbulent wall-bounded compressible flows. The proposed technique allows for accurate reproduction of outer layer turbulent dynamics and automatic switching between the two LES methods. Numerical simulations demonstrate the potential of the approach for predictive analysis of wall-bounded flows at high Reynolds numbers.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Davide Modesti, Srikanth Sathyanarayana, Francesco Salvadore, Matteo Bernardini
Summary: This study investigates the characteristics of supersonic turbulent channel flow over cubical roughness elements through direct numerical simulation. The results show that the Mach number has a significant impact on the mean velocity profile, while the thermal field is substantially affected by the roughness.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Green & Sustainable Science & Technology
Giacomo Della Posta, Stefano Leonardi, Matteo Bernardini
Summary: The study suggests that one-way coupled simulations tend to overestimate power production and structural oscillations in wind turbines. Flapwise blade vibration induces aerodynamic damping in the structural motion, while torsional deformation reduces power without introducing significant dynamical effects.
Article
Mechanics
Michele Cogo, Francesco Salvadore, Francesco Picano, Matteo Bernardini
Summary: The structure of high-speed zero-pressure-gradient turbulent boundary layers was studied using direct numerical simulation of the Navier-Stokes equations up to high Reynolds numbers, revealing the consequences in supersonic and hypersonic conditions. Instantaneous fields showed elongated strips of uniform velocity and temperature with clear associations between different streaks.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Aerospace
Fulvio Stella, Matteo Cimini, Burak Duendar, Francesca Rossetti, Daniele Barbagallo, Agostino Neri, Matteo Bernardini
Summary: This study presents a numerical investigation on the behavior of launchers during the free-fall phase, considering the fundamental parameters such as Mach number and incidence angle. The results show that the equilibrium position and stability of the launcher are influenced by these parameters.
JOURNAL OF SPACECRAFT AND ROCKETS
(2022)
Article
Mechanics
Matteo Bernardini, Giacomo Della Posta, Francesco Salvadore, Emanuele Martelli
Summary: The study investigates the impact of an oblique shock wave on a turbulent boundary layer through direct numerical simulation, simulating flow conditions similar to a previous experiment. The low-frequency shock unsteadiness is examined using the Morlet wavelet transform, revealing that the broadband shock movement is the result of sparse events with different temporal scales.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Energy & Fuels
Giacomo Della Posta, Stefano Leonardi, Matteo Bernardini
Summary: As horizontal axis wind turbines grow in size, they are exposed to various sources of unsteadiness. This study uses a 2D unsteady aerodynamics model to improve the description of blades' aerodynamic response and examines the aeroelastic response of a utility-scale wind turbine using fluid-structure interaction (FSI) solver. The results show that the external half of the blade is dominated by aeroelastic effects, while the internal half is influenced by significant unsteady aerodynamics phenomena.
Article
Engineering, Aerospace
Andrea Di Mascio, Emanuele Martelli, Matteo Bernardini, Fulvio Stella, Agostino Neri
Article
Engineering, Aerospace
Giacomo Della Posta, Marco Fratini, Francesco Salvadore, Matteo Bernardini
Summary: This study presents direct numerical simulations of a turbulent boundary layer on a microramp to investigate the impact of Mach number on the flow. The study finds that the flow topology changes significantly due to compressibility effects and the typical wake features are not linearly scaled with the geometry dimensions but depend on the incoming flow conditions. Furthermore, the study explores the spectral content in time and space of the wake, with Kelvin-Helmholtz instability dominating along the shear layer. The shedding onset is postponed and exhibits a lower peak frequency that evolves in space for larger Mach numbers.