Article
Mechanics
XianXu Yuan, YaLu Fu, JianQiang Chen, Ming Yu, PengXin Liu
Summary: In this study, the effects of spanwise-oriented grooves on the kinetic and thermodynamic statistics in a supersonic turbulent channel flow were investigated using direct numerical simulations. The results showed that these grooves induced compressive and expansive waves that traveled across the channel and influenced the distribution of vortices and streaks. These waves enhanced the fluctuations in temperature, density, and pressure, and also altered the correlations between velocity and temperature.
Article
Mechanics
Y. Zhang, S. Goertz, M. Oberlack
Summary: In this study, the reflection and over-reflection of acoustic waves in two-dimensional inviscid compressible boundary layer flows were analyzed. It was found that energy is always transferred from the base flow to the reflected wave in supersonic conditions, and this phenomenon is closely linked to the presence of the critical layer. Additionally, resonant over-reflection was observed, which is related to the resonant frequencies of unstable modes of the temporal stability of the base flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Zhigang Zhang, Fulin Tong, Junyi Duan, Xinliang Li
Summary: This study conducted a direct numerical simulation of an incident shock wave impinging on a 12° supersonic turbulent expansion corner at a 33.2° angle, revealing the significant influence of expansion on the physics of interaction. The expansion led to reduced wall pressure and separation bubble size, affecting the motion induced by the shock. The study also analyzed the evolution of the reattached boundary layer and the generation mechanism of skin friction.
Article
Engineering, Aerospace
Pavel Polivanov, Oleg Vishnyakov, Andrey Sidorenko
Summary: This paper discusses the problem of flow control in a turbulent boundary layer under conditions of transonic and supersonic free-stream velocities. A combined control device called the plasma wedge is described, which increases the momentum in the boundary layer to enhance its resistance to adverse pressure gradients and flow separation. Experimental and computational investigations are conducted on a rectangular flat plate, and the results show the formation of a streamwise vortex behind the actuator. Reasonable agreement between experimental and numerical data suggests the suitability of the Reynolds-averaged Navier-Stokes equations for solving the problem.
Article
Mechanics
Mostafa Aghaei-Jouybari, Junlin Yuan, Zhaorui Li, Giles J. Brereton, Farhad A. Jaberi
Summary: Direct numerical simulations were used to investigate the effects of roughness on supersonic turbulent channel flows. Results show that the turbulence is strongly influenced by the roughness topography and the associated shock patterns. Two-dimensional (2-D) roughness generates strong oblique shock waves, while three-dimensional (3-D) roughness results in weaker shocklets. The impingement of shocks on the wall leads to localized augmentations of turbulence shear production. The entropy generation and temperature values are higher in 2-D roughness cases compared to 3-D ones. The effects of roughness extend beyond the near-wall layer due to the presence of shocks.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Tongbiao Guo, Jian Fang, Ji Zhang, Xinliang Li
Summary: In this study, the effect of secondary flow induced by riblets on supersonic turbulent boundary layers over a compression ramp is investigated. The results show that the secondary flow leads to an increase in the size and intensity of the rolling motion, contributing to the increase of mean momentum flux and turbulent fluctuations. The separation area is also reduced by the presence of riblets, and the frequency of low-frequency motion is higher in the presence of riblets compared to the baseline case.
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
Mechanics
Xianliang Chen, Cheng Cheng, Lin Fu, Jianping Gan
Summary: The linear responses of turbulent mean flow to harmonic and stochastic forcing in supersonic channel flow are investigated in this study. Well-established universal relations are used to efficiently obtain mean profiles in a large parameter space, allowing for a systematic parameter study. The most amplified structure is streamwise velocity and temperature streaks forced by streamwise vortices. The pre-multiplied energy amplification peak corresponds to large-scale motion, which is insensitive to compressibility effects. The classic inner peak representing small-scale near-wall motions disappears with increasing Mach number for stochastic response.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Sourabh S. Diwan, Jonathan F. Morrison
Summary: The study proposed a three-layer asymptotic structure for turbulent pipe flow, revealing the existence of a Reynolds-number-invariant logarithmic region for the streamwise mean velocity and variance in terms of intermediate variables. The analysis determined the classical von Karman and Townsend-Perry constants from the intermediate-scaled log-law constants.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
G. G. Rooney
Summary: Dynamical constraints on the wall layer in turbulent pipe flow result in a narrow peak in the streamwise component of the turbulent Lamb vector near the wall, and a scaling relationship between the wall layer depth and the depth of the viscous sublayer. An approximation of the Lamb vector distribution, which is equivalent to the gradient of Reynolds stress, is proposed. Integration of the equation for streamwise mean flow allows for an expression of the velocity profile in the wall layer.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Aerospace
Julian Giehler, Pierre Grenson, Reynald Bur
Summary: This study investigates the influence of various design parameters on the efficiency and effectiveness of porous bleed systems by means of three-dimensional simulations. The findings show that the hole diameter has a crucial influence on both the efficiency and effectiveness of the porous bleed.
JOURNAL OF PROPULSION AND POWER
(2023)
Article
Mechanics
Rui Yang, Davide Modesti, Yu-xin Zhao, Qian-cheng Wang, Zhen-guo Wang, Sergio Pirozzoli
Summary: In this study, the Reynolds-averaged Navier-Stokes equations with a Reynolds stress model were used to investigate the impact of corner angles in supersonic flows. The parametric study revealed that the maximum strength of secondary flows occurred at 90 degrees, with their shape maintained by translating parallel to the nearest wall.
Article
Mechanics
V. I. Lysenko, S. A. Gaponov, B. V. Smorodsky, A. D. Kosinov, M. I. Yaroslavtsev
Summary: In this theoretical study, the properties of a supersonic boundary layer and its linear stability under conditions of surface material sublimation were investigated. It was found that surface sublimation leads to a decrease in disturbance amplification rates, resulting in a more stable boundary layer. Both experiments and calculations confirmed the potential of surface sublimation in delaying boundary layer transition.
Article
Mechanics
Nikolay Nikitin, Boris Krasnopolsky
Summary: A numerical investigation of turbulent flows in straight pipes with a circular sector cross-section is conducted, focusing on the cases with a convex external corner. It is found that the wall shear stress exhibits singularity at alpha > pi, which persists in turbulent flows. Secondary flows in the vicinity of the external corner are observed and attributed to the centrifugal force arising from fluctuating flow over the corner in the transverse plane. Linear stability analysis supports the hypothesis that the fluctuations are caused by the linear instability of the mean flow field.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Runjie Song, Ming Dong
Summary: In this paper, the instability of a boundary layer over a rotating cone in a supersonic flow with zero angle of attack is systematically studied. The instability characteristics for different rotating rates and Reynolds numbers are revealed, including the existence of modified Mack mode (MMM) and cross-flow mode (CFM), as well as the emergence of type-I and type-II instabilities. The vortex structures of these instability modes are compared, and their behaviors at high Reynolds numbers are discussed.
JOURNAL OF FLUID MECHANICS
(2023)
