Article
Mechanics
Y. X. Wang, K. -S. Choi, M. Gaster, C. Atkin, V. Borodulin, Y. Kachanov
Summary: The experimental investigation in a low-turbulence wind tunnel revealed that artificially initiated turbulent spots in a laminar boundary layer over a flat plate quickly developed into hairpin-like structures, increasing in width, length and height downstream. Only disturbances greater than a threshold value evolved into turbulent spots, while others decayed. The rate of development was also influenced by the duration of initial disturbances. Additionally, the behavior of turbulence generation within a turbulent spot was found to be similar to burst events in a turbulent boundary layer.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Y. X. Wang, K-S Choi, M. Gaster, C. Atkin, V Borodulin, Y. Kachanov
Summary: This study conducted opposition control of artificially initiated turbulent spots in a low-turbulence wind tunnel in order to delay the transition to turbulence by modifying the turbulent structure within the spots. Through wall-normal jets, the high-speed region of the turbulent spots was cancelled and replaced by a carpet of low-speed fluid. The variable-interval time-averaging technique showed a decrease in burst duration and intensity within the spots, but an increase in burst frequency.
JOURNAL OF FLUID MECHANICS
(2022)
Review
Mechanics
Xiaohua Wu
Summary: Transitional-turbulent spots play a crucial role in engineering flows by bridging the gap between laminar and turbulent states. Over the years, research on turbulent spots has expanded to various types of flows, including hypersonic boundary layer flow, turbomachinery flow, and complex flows. Important progress has been made in understanding the origin, growth, interaction, and self-organization of turbulent spots. Additionally, the hypothesis that transitional-turbulent spots are a fundamental module of fully turbulent boundary layers has been supported by the discovery of locally generated turbulent-turbulent spots. This review discusses these advancements and highlights future research directions.
ANNUAL REVIEW OF FLUID MECHANICS
(2023)
Article
Mechanics
S. Panday, J. M. Floryan
Summary: It is shown that streaks and rolls can be created in a controlled manner in fully developed shear layers using spatially distributed heating, with their spatial distribution dictated by the heating pattern. The method is applicable for any Reynolds number and heating intensity. The energy costs of streak formation in laminar flows have been determined.
Article
Physics, Multidisciplinary
Takumi Matsuzawa, Noah P. Mitchell, Stephane Perrard, William T. M. Irvine
Summary: Researchers have generated and controlled a confined state of turbulence using vortex rings as building blocks. They have studied its three-dimensional structure, energy budget, and tunability. This approach opens up new possibilities for sculpting and harnessing turbulent flows.
Article
Mechanics
J. Dagaut, M. E. Negretti, G. Balarac, C. Brun
Summary: The study presents results from a large-eddy simulation of a Blasius profile over a concave boundary, showing the emergence of two dominant wavelengths in the linear/transition region and turbulent region. The predicted spatial modes match well with the computed profiles for both dominant wavelengths of the Gortler instability under high Reynolds and Gortler numbers.
Article
Mechanics
Zisong Zhou, Chun-Xiao Xu, Javier Jimenez
Summary: The study found that the large-scale motions in the outer region of wall-bounded flows have a top-down influence on the spanwise motion of near-wall streaks. However, the density of streaks is weakly related to LSMs. Numerical experiments also showed that near-wall streaks merging is not strongly correlated with the generation of LSMs.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
H. Yao, G. Papadakis
Summary: This study investigates the role of the laminar/turbulent interface in the interscale energy transfer in a boundary layer undergoing bypass transition, using the Karman-Howarth-Monin-Hill (KHMH) equation. A local binary indicator function is used to detect the interface and define two-point intermittencies. The findings show that the inverse cascade in the streamwise direction is caused by events across the downstream or upstream interfaces of a turbulent spot, and there are significant differences in the energy fluxes between these two regions.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Markus Scherer, Markus Uhlmann, Aman G. Kidanemariam, Michael Krayer
Summary: The study reveals the connection between the formation of subaqueous sediment ridges and the lateral organization of large-scale streaks, with ridges mostly appearing below large-scale low-speed streaks. The adaptation of sediment bedforms to changes in the outer flow with a time delay is described as a 'top-down' process. The presence of mean secondary currents of comparable intensity and spacing over sediment ridges and smooth-wall channels indicates the influence of regularly organized large-scale streaks.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
R. Jackel, B. Magacho, B. E. Owolabi, L. Moriconi, D. J. C. Dennis, J. B. R. Loureiro
Summary: Using stereoscopic particle image velocimetry, we investigated coherent states in a large diameter pipe loop in the moderate Reynolds number range (5300 < Re < 29 000). We discovered ten well-defined coherent flow patterns, whose occurrence probabilities and number of dominant modes remain constant regardless of Reynolds number variations. These low-speed streaks appear to be generated as a Poisson process on the pipe circular geometry.
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
X. Y. Jiang, D. W. Gu, C. B. Lee, C. R. Smith, P. F. Linden
Summary: The study explores the laminar-turbulent transition in boundary layers by investigating the evolution of flow structures from 3-D waves to Lambda-vortices. Through numerical simulations of K-regime and bypass transitions, the process of wave-warping and vortex dynamics is examined. The research suggests that adverse pressure gradient conditions lead to a more rapid evolution and stronger viscous-inviscid interaction, ultimately resulting in the development of high-shear layers and warped wave fronts.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Aerospace
Christoph Hader, Hermann F. Fasel
Summary: Several experimental investigations of hypersonic boundary-layer transition have observed higher harmonics of the linearly unstable second mode waves and low-frequency waves that are not related to first mode waves. The higher harmonics are believed to be nonlinearly generated by a self-interaction mechanism of the linearly amplified second mode waves. Hypotheses regarding the origin and role of the low-frequency waves in the transition process have been proposed but a clear understanding is still lacking. Numerical investigations and theoretical models have shown that large-amplitude second mode waves can generate low-frequency disturbances in high-speed boundary layers.
Article
Mechanics
T. Medjnoun, E. Rodriguez-Lopez, M. A. Ferreira, T. Griffiths, J. Meyers, B. Ganapathisubramani
Summary: This experimental study investigates the effects of roughness-scale hierarchy on turbulent boundary layers using multiscale rough surfaces with regular elements. The aerodynamic roughness length scale between iterations varies linearly and the contribution of different roughness iterations to the overall drag varies. The presence of large-scale secondary motions in the cross-plane is shown to cause substantial changes in the flow field, with implications on classical similarity laws.
JOURNAL OF FLUID MECHANICS
(2021)
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
Engineering, Electrical & Electronic
Dmitry Kozlov, Alexey P. Shitvov, Senad Bulja, Ross Lundy, Pawel Rulikowski, Kevin Nolan, Ryan Enright
IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY
(2020)
Letter
Gastroenterology & Hepatology
J. Dalli, M. F. Khan, K. Nolan, R. A. Cahill
COLORECTAL DISEASE
(2020)
Article
Chemistry, Multidisciplinary
Cristian Soitu, Nicholas Stovall-Kurtz, Cyril Deroy, Alfonso A. Castrejon-Pita, Peter R. Cook, Edmond J. Walsh
Article
Pharmacology & Pharmacy
Marc Mac Giolla Eain, Ronan Cahill, Ronan MacLoughlin, Kevin Nolan
Summary: Aerosol therapy is commonly used to treat respiratory conditions, but it can lead to the release of fugitive aerosols that may pose a risk to healthcare workers and bystanders. This study simulated the release of fugitive aerosols during aerosol therapy for adult patients and found that adding a bacterial filter to the mouthpiece significantly reduced the release of these aerosols.
Article
Multidisciplinary Sciences
Caroline Crowley, Brian Murphy, Conan McCaul, Ronan Cahill, Kevin Patrick Nolan
Summary: High Flow Nasal Oxygen (HFNO) therapy, commonly used for critically ill patients with viral illness, can increase the risk of disease transmission to healthcare workers. This study examined the effect of HFNO therapy on aerosol dispersion patterns during exhalation. It was found that HFNO therapy increased turbulence in the exhalation jet and significantly affected the travel distance of small droplets. The study highlights the importance of understanding the fluid dynamics of exhalation when using HFNO therapy to mitigate infection risks.
Review
Chemistry, Physical
Cyril Deroy, Federico Nebuloni, Peter R. Cook, Edmond J. Walsh
Summary: The article discusses an open microfluidic approach that creates aqueous circuits with almost any 2D shape on standard polystyrene Petri dishes, allowing for easy cell growth and observation. This fluid-shaping technology aims to provide a simple, accessible, and affordable entrance into microfluidics for bioscientists.
Article
Mechanics
Caroline Crowley, Ronan Cahill, Kevin Nolan
Summary: This study used a computational fluid dynamics model to simulate the gas leakage during laparoscopic surgery and quantified the percentage of particulate matter that poses a risk of inhalation to the surgical staff. The results showed that a significant amount of particles reach the breathing zone of the surgical team, and the gas leakage emits a considerable volume of gas and particles into the operating room.
Article
Materials Science, Multidisciplinary
Cyril Deroy, Agata N. Rumianek, James H. R. Wheeler, Federico Nebuloni, Peter R. Cook, David R. Greaves, Edmond J. Walsh
Summary: This study utilizes fluid-walled microfluidics to build circuits for studying immune-cell chemotaxis. By establishing concentration gradients of C5a, the migration of cells can be observed and the relationship between cell directionality and velocity with local C5a concentrations can be analyzed.
ADVANCED MATERIALS TECHNOLOGIES
(2022)
Article
Anesthesiology
Marc Mac Giolla Eain, Kevin Nolan, Brian Murphy, Conan McCaul, Ronan MacLoughlin
Summary: Awake Tracheal Intubation (ATI) is a potential risk for healthcare workers due to the generation of aerosol particles. This study used optical particle sizers to observe aerosol distribution during a simulated ATI with high-flow nasal oxygen therapy. The highest concentration of patient-derived aerosol particles was within 0.5-1.0 m of the subject, while particles > 5 μm spread radially throughout the operating room. It is recommended that full airborne protective equipment be worn by all staff during ATI on patients with suspected viral respiratory infections.
JOURNAL OF CLINICAL MONITORING AND COMPUTING
(2023)
Article
Surgery
N. Hardy, J. Dalli, M. F. Khan, K. Nolan, R. A. Cahill
Summary: Laparoscopic surgery has been questioned during the COVID-19 pandemic due to concerns about infectious risks through aerosolization of peritoneal particles. There is a need for increased awareness of the occupational hazards for surgical teams related to unfiltered pollutants escaping during surgery. Real-time methods confirmed the aerosol-generating nature of laparoscopic surgery, providing best practices and engineering solutions for optimizing the operating room environment.
BRITISH JOURNAL OF SURGERY
(2021)
Letter
Surgery
N. McInerney, M. F. Khan, K. Nolan, R. A. Cahill
BRITISH JOURNAL OF SURGERY
(2021)
Article
Biochemical Research Methods
Cristian Soitu, Mirela Panea, Alfonso A. Castrejon-Pita, Peter R. Cook, Edmond J. Walsh
Summary: This experiment introduces a contactless method to create wounds with any imaginable 2D pattern in cell monolayers, combined with automation and multiplexing techniques. By using standard Petri dishes, it is anticipated that this assay will find wide application in wound healing research.
Letter
Surgery
J. Dalli, M. F. Khan, K. Nolan, R. A. Cahill
BRITISH JOURNAL OF SURGERY
(2021)
Letter
Surgery
N. McInerney, C. Gilligan, L. Manojlovich, M. F. Khan, K. Nolan, R. A. Cahill
BRITISH JOURNAL OF SURGERY
(2021)
Proceedings Paper
Engineering, Aerospace
C. H. Hsu, H. Y. Lin, A. Agarwal, I. Davis, K. P. Nolan, K. B. Lua
10TH ASIAN-PACIFIC CONFERENCE ON AEROSPACE TECHNOLOGY AND SCIENCE & THE 4TH ASIAN JOINT SYMPOSIUM ON AEROSPACE ENGINEERING (APCATS'2019 /AJSAE'2019)
(2020)
