Article
Mathematics
Ben Duan, Chunpeng Wang, Yuanyuan Xing
Summary: This paper focuses on the steady Euler-Poisson system in a two-dimensional divergent nozzle with finite length. It transforms the structural stability of supersonic potential flows into the well-posedness of a second order quasilinear hyperbolic-elliptic coupled system with nonlinear boundary conditions. By combining the iteration method with estimates for the hyperbolic-elliptic system, the well-posedness and the nonlinear structural stability of such supersonic flows under perturbations of boundary conditions are established.
JOURNAL OF DIFFERENTIAL EQUATIONS
(2023)
Article
Mechanics
Xiao Lian, Hao Xu, Lei Duan, Tiezhi Sun
Summary: Supersonic gas jets in conical convergent-divergent nozzles are numerically studied using the OpenFOAM rhoCentralFoam solver. The effects of operating conditions on the flow field, including nozzle pressure ratio (NPR), area ratio, and throat position, are parametrically investigated. The behaviors and mechanisms of the double-diamond structure, throat wave, and exit wave are analyzed in detail. The results indicate that shock waves are always generated in a conical convergent-divergent nozzle. The length of the throat shock reaches its maximum during the initial stage, becomes slightly shorter before becoming stationary, which is dominated by the exit velocity. Moreover, the jet flow transitions from overexpansion to underexpansion as the NPR increases, while the trend is opposite with increasing area ratio. The throat position affects the divergence angle and core radius of the jet at the nozzle exit. Furthermore, the presence of the double-diamond structure is influenced by the throat shock angle, exit wave angle, and shear layer width. The changes in the length of the throat wave and exit wave are ultimately controlled by the favorable pressure gradient of the nozzle.
Article
Materials Science, Multidisciplinary
Milaan Patel, Jinto Thomas, Hem Chandra Joshi
Summary: In this paper, we conduct experimental investigation on improving the shape of a supersonic nozzle for rarefied flows at extended distances. The work is significant for molecular jet/beam applications that require high center-line density and narrow jet profile. We compare a parabolic nozzle with conical nozzles of different cone angles using simulations and experiments, and measure the axial density and lateral spread of the jets. The study shows that the parabolic nozzle performs comparably or slightly better than the conical counterparts, and its profile can be used for optimizing the opening angle of conical nozzles.
Article
Thermodynamics
Tao Yang, Yanhua Sun, Liang Xu, Lei Xi, Jianmin Gao, Yunlong Li
Summary: This study compares the flow and heat transfer characteristics of spiral rod, twisted tape, guide vane, and thread grooves nozzles through numerical and experimental analysis. The experimental results show that the thread grooves nozzle has the highest Nusselt number in the stagnation region, while the spiral rod nozzle has the highest Nusselt number in the central area. The numerical results indicate that the spiral rod nozzle has the best heat transfer performance and uniformity, and it is influenced by the swirl angle.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Mathematics, Applied
Geng Lai, Wancheng Sheng
Summary: This paper studies the flow characteristics of supersonic jet flows, including cases where the jet enters a vacuum and the atmosphere. The authors propose a continuous and piecewise smooth supersonic reacting jet flow model and explain the formation of intercepting shocks in supersonic jets in a low-pressure environment.
SIAM JOURNAL ON MATHEMATICAL ANALYSIS
(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
Mathematics
Ben Duan, Ao Lan, Zhen Luo
Summary: This paper studies the transonic shock solutions in a quasi-one-dimensional divergent-convergent nozzle for the steady Euler system. Two non-isentropic transonic shock solutions are derived for the exit pressure within a suitable range, based on a given physical supersonic inflow at the entrance. Moreover, the monotonicity between the location of the transonic shock and the pressure downstream is established.
ACTA MATHEMATICA SCIENTIA
(2022)
Article
Thermodynamics
Susila Mahapatra, Somnath Ghosh
Summary: This study investigates the compressible turbulent flow through canonical convergent-divergent nozzles with circular cross-section. The results show that flow expansion and local flow compression have substantial effects on the mean flow and turbulence structure.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2022)
Article
Mathematics, Applied
Gang Xu, Huicheng Yin
Summary: This paper investigates the global existence and stability of a smooth supersonic Euler flow with vacuum state at infinity in a three-dimensional infinitely long divergent nozzle. It shows that the compressible Euler equations are degenerate at infinity due to the gradually rarefactive gases moving in the divergent nozzle. The study also proves the global stability of the 3-D Euler flow and the absence of vacuum domains in the nozzle for small initial perturbations.
SIAM JOURNAL ON MATHEMATICAL ANALYSIS
(2021)
Article
Mechanics
Junze Ji, Zhufei Li, Enlai Zhang, Dongxian Si, Jiming Yang
Summary: This study investigates the characteristics and mechanism of near-conical shocks when the flow deviates from axial symmetry. The findings show that as the shock converges downstream, the circumferential non-uniformity intensifies, causing the Mach disk to shrink and flatten slightly.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Thermodynamics
Julian C. Restrepo, Andres F. Bolanos-Acosta, Jose R. Simoes-Moreira
Summary: This paper presents a method of using multi-parameter equations-of-state to design supersonic nozzles for real gases, and compares the results with other classical equations-of-state to evaluate their optimal application range.
APPLIED THERMAL ENGINEERING
(2022)
Article
Mechanics
Alessandro Ferrari
Summary: New analytical solutions have been obtained for the one-dimensional steady-state compressible viscous adiabatic flow of an ideal gas through a conical nozzle or diffuser. The solutions have been validated through dimensionless representation and fluid dynamics analysis for both subsonic and supersonic flows. The proposed solutions complement existing models and expand the collection of exact solutions in gas dynamics.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Guanming Gai, Yuanyuan Nie, Chunpeng Wang
Summary: This paper examines continuous subsonic-sonic potential flows in a two-dimensional converging nozzle, demonstrating the existence of a unique flow state with certain characteristics given a specific nozzle and mass flux. The study highlights the singular nature of the flow near the sonic state, where velocity is Holder continuous and acceleration diverges.
COMMUNICATIONS ON PURE AND APPLIED ANALYSIS
(2021)
Article
Mechanics
Aibo Wei, Lianyan Yu, Rong Gao, Wei Zhang, Xiaobin Zhang
Summary: This study investigates the shedding mechanism of cloud cavitation in cryogenic liquids through experimental and numerical simulations. It reveals that the re-entrant jet and condensation shock are the dominant mechanisms for shedding of cloud cavitation, offering a deeper understanding of the phenomenon.
Article
Engineering, Aerospace
Guangli Fan, Adel Almarashi, Peixi Guo, Nidal H. Abu-Hamdeh, Abdullah M. Abusorrah, R. Moradi
Summary: The study investigates the impacts of high-velocity air stream interacting with cross fuel jet on fuel mixing and flame stability. Computational fluid dynamic method is used to model the flow structure, revealing that adding an inclined ramp upstream can enhance fuel mixing effectiveness and distribution uniformity.
AEROSPACE SCIENCE AND TECHNOLOGY
(2022)
Article
Chemistry, Physical
Robert Driscoll, Andrew St George, Ephraim J. Gutmark
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2016)
Article
Chemistry, Physical
Robert Driscoll, Paul Aghasi, Andrew St George, Ephraim J. Gutmark
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2016)
Article
Chemistry, Physical
Vijay Anand, Andrew St. George, Robert Driscoll, Ephraim Gutmark
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2016)
Article
Engineering, Mechanical
Erwann Guillou, Matthieu Gancedo, Ephraim Gutmark
JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME
(2016)
Review
Thermodynamics
Dan Zhao, Ephraim Gutmark, Philip de Goey
PROGRESS IN ENERGY AND COMBUSTION SCIENCE
(2018)
Article
Dentistry, Oral Surgery & Medicine
Liran Oren, Michael Rollins, Srujana Padakanti, Ann Kummer, Ephraim Gutmark, Suzanne Boyce
CLEFT PALATE-CRANIOFACIAL JOURNAL
(2020)
Article
Mechanics
Bernhard Semlitsch, Bhupatindra Malla, Ephraim J. Gutmark, Mihai Mihaescu
JOURNAL OF FLUID MECHANICS
(2020)
Article
Mechanics
Yazhou Shen, Mohamad Ghulam, Kai Zhang, Ephraim Gutmark, Christophe Duwig
Editorial Material
Mechanics
E. J. Gutmark
Article
Biophysics
Ephraim Gutmark, Vijay Anand, Aaron Wheeler, Alexander Zahn, Yuval Cavari, Tal Eluk, Maor Hay, David Katoshevski, Iris Gutmark-Little
Summary: Intrapulmonary Percussive Ventilation (IPV) is a high-frequency airway clearance technique that helps in mucus removal for mechanically ventilated and unventilated patients. However, there is a lack of clear evidence on its effectiveness. This article proposes a novel method utilizing a high-frequency acoustic field and traditional IPV to slowly push the mucus simulant towards the mouth.
JOURNAL OF BIOMECHANICS
(2022)
Article
Mechanics
Myeonghwan Ahn, Mihai Mihaescu, Aatresh Karnam, Ephraim Gutmark
Summary: In this study, the flow and aeroacoustics of twin square jets with an aspect ratio of 1.0 were investigated using implicit large-eddy simulations (LES) under specific conditions. The study revealed the presence of screeching twin jets in a symmetrical flapping mode, characterized by intense pressure fluctuations and standing waves between the jets. The results from spectral proper orthogonal decomposition (SPOD) and solving Ffowcs Williams and Hawkings equation for far-field noise were in good agreement with experimental data. The study also found different levels of screech tone produced by the twin jets depending on the observation planes.
Article
Mechanics
A. Karnam, M. Saleem, E. Gutmark
Summary: This study discusses the influence of nozzle exit geometry on the interaction between convective Kelvin-Helmholtz instabilities and the shock structure of supersonic jets. Circular and rectangular nozzles with an aspect ratio of 2 were evaluated using near field acoustics and Schlieren images. The study observed different screech instabilities in both nozzle configurations and found comparable trends in screech behavior. The results also revealed that the oscillation mode of the jets influenced the standing waves in the jet near field.
Article
Mechanics
M. Saleem, A. Karnam, O. Rodriguez, J. Liu, E. Gutmark
Summary: The role of micro-vortex generators (MVGs) in reducing supersonic jet noise is investigated in this study. Experimental and numerical simulation results show that MVGs can interact with the shock cell structure of the jet plume and modify its core velocities, leading to a significant reduction in jet noise. These findings have important implications for the design and development of noise reduction technologies for supersonic jet engines.
Article
Mechanics
M. D. Bohon, A. Orchini, R. Bluemner, C. O. Paschereit, E. J. Gutmark
Summary: The study analyzed the application details of dynamic mode decomposition (DMD) technique in rotating detonation combustor. It is able to capture well the dominant oscillatory features corresponding to stable limit-cycle or quasi-periodic behavior.
Review
Thermodynamics
Vijay Anand, Ephraim Gutmark
INTERNATIONAL JOURNAL OF SPRAY AND COMBUSTION DYNAMICS
(2019)