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
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
Chemistry, Physical
Yuelei Zhang, Puneet Rana, R. Moradi, Zhixiong Li
Summary: This study investigates the impact of coaxial injector arrays of hydrogen/air multi-jet on fuel mixing performance, aiming to optimize fuel distribution and penetration downstream in different operating conditions. The results show that the injection of coaxial air/hydrogen jet significantly enhances mixing downstream and the fuel jet space of 7 Dj offers maximum fuel mixing.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Environmental Sciences
Jens von der Linden, Clare Kimblin, Ian McKenna, Skyler Bagley, Hsiao-Chi Li, Ryan Houim, Christopher S. Kueny, Allen Kuhl, Dave Grote, Mark Converse, Caron E. J. Vossen, Soenke Stern, Corrado Cimarelli, Jason Sears
Summary: The text discusses how sparks and standing shocks observed in shock tube experiments regulate electrical breakdown, and how radio frequency signatures emitted by volcanic eruptions can diagnose fluid dynamic and electrostatic conditions. Research shows that sparks are initiated in a rarefaction region and cut off at the shock, limiting their radio frequency emissions to a characteristic frequency range.
COMMUNICATIONS EARTH & ENVIRONMENT
(2021)
Article
Thermodynamics
H. Kbab, O. Abada, S. Haif
Summary: This paper presents a study on the simulation of flow in a dual bell nozzle, using computational fluid dynamics (CFD) to understand and optimize the design of the nozzle.
JOURNAL OF APPLIED FLUID MECHANICS
(2023)
Article
Thermodynamics
Marco Manfredi, Giacomo Persico, Andrea Spinelli, Paolo Gaetani, Vincenzo Dossena
Summary: In organic Rankine cycle (ORC) power systems, the design of ORC turbines heavily relies on advanced aerodynamic models, but the validation of these models is limited due to a lack of experimental data. To fill this gap, an experimental campaign on supersonic ORC nozzle cascades has been launched at Politecnico di Milano. This paper describes the conception and set-up of a novel class of experiments on linear cascades representative of stator nozzles of axial/radial ORC turbines and aims at providing a benchmark for numerical simulations.
APPLIED THERMAL ENGINEERING
(2023)
Article
Mathematics, Applied
Chunpeng Wang
Summary: This paper discusses the global existence of smooth sonic-supersonic potential flows in a two-dimensional expanding nozzle and its relation to the geometry of the inlet. It presents a special model and establishes conditions for the existence using a method of characteristics.
SIAM JOURNAL ON MATHEMATICAL ANALYSIS
(2022)
Article
Energy & Fuels
M. Barzegar Gerdroodbary, R. Moradi, Houman Babazadeh
Summary: This study investigates the influence of free stream angles on fuel mixing in scramjet design, showing that a positive angle can lead to more uniform expansion of the fuel mixing zone. Increasing the angles of the free stream reduces the mixing zone when the fuel jet interaction decreases, with a mixing efficiency of -20 degrees about 30% more than other angles.
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
(2021)
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
Sergey F. Gimelshein, Ingrid J. Wysong
Summary: A new method based on the direct simulation Monte Carlo method is proposed to model core flow in a converging-diverging nozzle, with validation through comparison with experimental data. The study shows that nitric oxide (NO) density is highly sensitive to exchange reactions and NO recombination rates under specific conditions, while being less affected by nonequilibrium. Additionally, vibration-dissociation coupling has a significant influence on mole fractions of NO and O-2 under different shock tunnel conditions.
Article
Engineering, Aerospace
Yongchan Kim, Junyeop Nam, Tae-Seong Roh, Hyoung Jin Lee
Summary: This study analyzed the base drag and flow characteristics of cold and hot gas flow in a supersonic flow through numerical simulations. The results showed that the change in base drag ranged from 5% to 85% depending on the injection gases. The base drag in hot gas flow exhibited different variations under different conditions, and the flow structures also differed from those in cold flow.
Article
Thermodynamics
Mustafa Atmaca, Berkay Cetin, Cuneyt Ezgi, Ergin Kosa
Summary: Nozzles are commonly used in engineering to control flow parameters. This paper presents the predicted performance of jet flows from different shaped nozzles using a CFD model, with results matching experimental data.
INTERNATIONAL JOURNAL OF LOW-CARBON TECHNOLOGIES
(2021)
Article
Optics
Walker McCord, Mark Gragston, David Plemmons, Zhili Zhang
Summary: This study develops a novel non-intrusive technique for characterizing thermal gradients within supersonic and hypersonic flows. By directly imaging Resonantly Ionized Photoemission Thermometry (RIPT) signals, detailed flow characterizations are achieved for experimental validation of computational simulations.
Article
Mechanics
E. McLean, R. Bowles, B. Scheich, J-M Vanden-Broeck
Summary: This study investigates the two-dimensional free-surface flow over the edge of a plate forming a waterfall. Numerical solutions are used to demonstrate the improved shape of the new free-surface profiles. Different methods are employed for flows with different Froude numbers, resulting in enhanced coefficient decay.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Mechanical
Hamid Nasirzadeh, Mohammad Eftekhari Yazdi, Arash Mirabdolah Lavasani
Summary: Different jet configurations were tested to reduce the surface temperature of a constant heat flux plate. The study found that the simultaneous use of two swirling jets achieved both increased overall Nusselt number and decreased maximum temperature on the hot surface.
JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING
(2022)
Article
Engineering, Aerospace
F. Gnani, H. Zare-Behtash, C. White, K. Kontis
Article
Physics, Fluids & Plasmas
Michael M. Wojewodka, Craig White, Takahiro Ukai, Andrew Russell, Konstantinos Kontis
PHYSICS OF PLASMAS
(2019)
Article
Chemistry, Multidisciplinary
Kin-Hing Lo, Rengarajan Sriram, Konstantinos Kontis
APPLIED SCIENCES-BASEL
(2019)
Article
Mechanics
S. M. Mortazawy, K. Kontis, J. Ekaterinaris
Article
Engineering, Aerospace
Guoshuai Li, Takahiro Ukai, Konstantinos Kontis
AEROSPACE SCIENCE AND TECHNOLOGY
(2019)
Article
Energy & Fuels
Takahiro Ukai, Konstantinos Kontis
Article
Engineering, Aerospace
Erinc Erdem, Konstantinos Kontis
Summary: An experimental investigation of sonic transverse jets in Mach 5 cross flow over a flat plate with a sharp leading edge was conducted to study jet penetration characteristics and flow structures. Schlieren visualization and steady wall pressure measurements provided insights into flow features and interaction regions at different momentum flux ratios.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Mechanics
Ziqu Cao, Craig White, Konstantinos Kontis
Summary: The study investigates the formation and evolution of vortex loops caused by shock wave diffraction around a 90 degrees corner under rarefied flow conditions. The effects of Mach number and rarefaction on the vortex loop are discussed, along with the discovery of a relationship between vorticity and shear vectors through the application of the vorticity concept.
Article
Engineering, Aerospace
Michael M. Wojewodka, Craig White, Shahrokh Shahpar, Konstantinos Kontis
Summary: The flow through the Wellborn s-duct is investigated using the open source computational fluid dynamics software OpenFOAM. Numerical simulations with two different modelling techniques, URANS and DDES, are compared and validated against experimental data. The results show that the DDES simulations closely match the experimental data, offering promise for a tailored, active flow control strategy.
AEROSPACE SCIENCE AND TECHNOLOGY
(2022)
Article
Computer Science, Interdisciplinary Applications
Z. Cao, M. B. Agir, C. White, K. Kontis
Summary: This paper presents the development and benchmarking tests of an open source code for solving two-phase rarefied flows. The code can provide steady and transient results for arbitrary 2D/3D two-phase rarefied flows and includes a phase change model. The benchmarking tests show good agreement with analytical and experimental data, and are compared to previous numerical results from the literature.
COMPUTER PHYSICS COMMUNICATIONS
(2022)
Article
Mechanics
M. B. Agir, C. White, K. Kontis
Summary: This study investigates the formation of Edney shock patterns under different rarefaction levels caused by shock-shock interactions in high-speed vehicles. The research shows that increasing rarefaction leads to a larger region with enhanced thermo-mechanical loads, while peak values decrease.
Article
Engineering, Aerospace
Naser Al Haddabi, Konstantinos Kontis, Hossein Zare-Behtash
Summary: Increasing the jet momentum flux leads to an increase in cavity return flow due to thickening of the separated shear layer, while the jet introduces a large number of small-scale disturbances into the separated shear layer, increasing the broad band level of pressure power spectra and Reynolds shear stress.
Proceedings Paper
Engineering, Aerospace
Guoshuai Li, Muhammed BurakAgir, Konstantinos Kontis, Takahiro Ukai, Sriram Rengarajan
2018 THE 9TH ASIA CONFERENCE ON MECHANICAL AND AEROSPACE ENGINEERING
(2019)
Article
Engineering, Aerospace
Chengpeng Wang, Xin Yang, Longsheng Xue, Konstantinos Kontis, Yun Jiao
Proceedings Paper
Engineering, Aerospace
Azam Che Idris, Mohd Rashdan Saad, Kin Hing Lo, Konstantinos Kontis
INTERNATIONAL CONFERENCE ON AEROSPACE AND MECHANICAL ENGINEERING (AEROMECH17)
(2018)
