Article
Mechanics
Michael N. Stavropoulos, Matteo Mancinelli, Peter Jordan, Vincent Jaunet, Joel Weightman, Daniel M. Edgington-Mitchell, Petronio A. S. Nogueira
Summary: Spatial linear stability analysis is used to study the axisymmetric screech tones generated by twin converging round nozzles. Different waves supported by the flow at different conditions are identified using vortex-sheet and finite-thickness models. The frequency-wavenumber regions at which the upstream-propagating guided jet modes are neutrally stable vary with solution symmetry, jet separation, S, and the velocity profile. Screech-frequency predictions from both models agree well with experimental data, but the predictions from the finite-thickness model match the measured screech tones better than the vortex sheet. The present results suggest that the feedback loop generating these screech tones is similar to that observed for single-jet resonance.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Fluids & Plasmas
Girish K. Jankee, Bharathram Ganapathisubramani
Summary: In flow control, using an array of synthetic jet actuators is more practical than a single actuator. Through a parametric study, it was found that twin jets operated at a specific phase difference and spacing can be more efficient for flow entrainment and momentum distribution.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Hendrik Reese, Robin Schaedel, Fabian Reuter, Claus-Dieter Ohl
Summary: This study investigates the directed jet flow generated by a cavitation bubble near a rigid boundary, which acts as a pump to transport liquid through a perforated plate. The transport process is complex and dependent on various factors, such as the geometry of the bubble and connecting channel, liquid viscosity, and stand-off distance of the bubble to the plate. The results show that the flow rate and velocity of the jet are influenced by these factors. Additionally, different types of jet flow, such as needle jet and reverse jet, are observed under different conditions.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Multidisciplinary
KrishnaKumar Rajnath Yadav, Akshoy Ranjan Paul, Anuj Jain
Summary: The study investigated the effects of single-offset and dual-offset twin air-intakes at various inlet Reynolds numbers using synthetic jets. Results showed that slotted synthetic jets can significantly reduce flow separation and enhance static pressure recovery. Furthermore, the single-offset twin air-intake exhibited less total pressure loss compared to the dual-offset one for all Reynolds numbers.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Mechanics
Ben Steinfurth, Julien Weiss
Summary: The experimental study investigated the interaction between starting jets and a steady cross-flow, finding different flow structures when compressed air is injected into a rectangular outlet. The results can aid in the selection of appropriate actuation parameters in active mixing and separation control.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Giuseppe Anaclerio, Tommaso Capurso, Marco Torresi
Summary: Green hydrogen is expected to play a key role in achieving a carbon-neutral society, especially in the transportation sector. This study investigates the gas-dynamic and mixing characteristics of hydrogen jets exiting from non-axisymmetric cross-sections, aiming to provide guidelines for designing advanced hydrogen injectors for internal combustion engines. The results reveal differences in shock wave systems and gas-dynamic mechanisms among different cross-sections, as well as non-uniformity in radial expansion and axial penetration of the jets.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Shirin Patil, Srikrishna Sahu
Summary: The paper reports on spray characterization in a novel twin-jet airblast injector, focusing on the effect of injector air swirl on droplet characteristics and dispersion behavior. The addition of air swirl significantly affects spray topology and droplet size downstream of the injector exit, leading to improved atomization quality and high spray dispersion. The results provide insight into the physics behind the improved atomization due to air swirl and demonstrate the injector's ability to achieve atomization quality and high spray dispersion over a wide operating range.
Article
Engineering, Mechanical
Xin-Yao Li, Ya-Fang Guo, Yong Mao, Xiao-Zhi Tang
Summary: The nucleation and growth of {1011} twin in Mg single crystal are investigated through molecular dynamics simulations. The twin embryo is found to be naturally nucleated at the free surface via dislocation slip, and its growth involves the formation of basal stacking faults.
INTERNATIONAL JOURNAL OF PLASTICITY
(2022)
Article
Engineering, Mechanical
Mahsa Janati, Amir Hossein Azimi
Summary: The evolution of single and twin oblique particle clouds in stagnant water was investigated in laboratory experiments, with parameters such as sand mass and nozzle spacing being studied. The effects of release angle and particle interactions on the clouds were analyzed, showing that the velocity of twin oblique particle clouds increased with nozzle spacing. Particle interactions due to frontal head collision in twin oblique particle clouds significantly increased the cloud width until reaching the swarm phase.
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
(2021)
Article
Mechanics
Cheolgyun Jung, Minho Song, Daegyoum Kim
Summary: This study investigates the formation of a starting jet through a novel eversion process using a vortex generator model. By varying geometric and kinematic parameters, such as the length and bending rigidity of the everting sheets, the study examines their effects on the deformation of the sheets and the formation of the jet. The interaction between the starting jet and the everting sheets enables a faster jet with an improved hydrodynamic impulse to be developed within a shorter stroke time.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
M. Mosavati, R. Balachandar, R. M. Barron
Summary: This study focuses on the behavior of self-oscillating twin jets in a narrow cavity, with computational fluid dynamics simulations revealing significant effects of nozzle spacing on oscillation frequency and turbulence characteristics. Comparison between round and square twin jets showed minimal impact of nozzle shape on jet decay, while twin oscillating jets were found to produce higher turbulence intensity over a wider area, potentially beneficial for cooling hot devices in industrial applications.
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
Food Science & Technology
Raphael Aidoo, Ebenezer M. Kwofie, Peter Adewale, Edmond Lam, Michael Ngadi
Summary: Single-cell protein (SCP) is an evolving biotechnological concept that aligns protein production with global sustainability goals. This review provides an overview of SCP's current outlook, discussing production, commercial prospects, and sustainability. It also explores the potential of the emerging digital twin concept in enhancing SCP production's efficiency and sustainability.
TRENDS IN FOOD SCIENCE & TECHNOLOGY
(2023)
Article
Mechanics
Jiaojiao Chen, Feng Qu, Xuanting Wu, Zirui Wang, Junqiang Bai
Summary: This paper investigates the interaction between shock waves and bubbles with different shapes, revealing that vorticity generation and distribution play a crucial role in bubble deformation, and the aspect ratio affects the degree of deformation and collapse speed of bubbles.
Article
Thermodynamics
Yohei Kubo, Sayaka Yamada, Hideki Murakawa, Hitoshi Asano
Summary: Frictional pressure drop and flow patterns of vertically upward boiling flows in semi-circular mini-channels were experimentally investigated using R-245fa as the working fluid. It was found that the gas Weber number increased with increasing mass flux and decreasing hydraulic diameter, and nucleate boiling leading to strong fluctuation of the gas-liquid interface was observed in the 0.55 mm channel.
APPLIED THERMAL ENGINEERING
(2021)
Article
Biophysics
Lisa Prahl Wittberg, Stevin van Wyk, Laszlo Fuchs, Ephraim Gutmark, Philippe Backeljauw, Iris Gutmark-Little
BIOMECHANICS AND MODELING IN MECHANOBIOLOGY
(2016)
Article
Thermodynamics
Vijay Anand, Andrew St George, Robert Driscoll, Ephraim Gutmark
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(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)
Article
Engineering, Biomedical
Dhananjay Radhakrishnan Subramaniam, Goutham Mylavarapu, Keith McConnell, Robert J. Fleck, Sally R. Shott, Raouf S. Amin, Ephraim J. Gutmark
ANNALS OF BIOMEDICAL ENGINEERING
(2016)
Article
Engineering, Biomedical
Dhananjay Radhakrishnan Subramaniam, Goutham Mylavarapu, Keith McConnell, Robert J. Fleck, Sally R. Shott, Raouf S. Amin, Ephraim J. Gutmark
ANNALS OF BIOMEDICAL ENGINEERING
(2016)