Article
Computer Science, Interdisciplinary Applications
Akhil Nekkanti, Oliver T. Schmidt
Summary: An algorithm based on spectral proper orthogonal decomposition (SPOD) is developed to reconstruct flow data in compromised or missing regions. The algorithm utilizes the temporal and spatial correlation of the SPOD modes to fill in the gaps. The method is demonstrated on two examples and achieves higher data recovery rates compared to established methods.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Mathematics, Applied
Y. Zhang, M. Vanierschot
Summary: A three-dimensional incompressible annular jet was simulated using the large eddy simulation (LES) method at a Reynolds number Re = 8 500. The study focused on the flow dynamics of the wake flow, with particular attention to the proper orthogonal decomposition (POD) analysis of the velocity fluctuation vectors. The results showed that the first four eigenmodes captured significant turbulent kinetic energy, impacting the wake dynamics, with modes 1 and 2 related to a radial shift of the stagnation point, and modes 3 and 4 involving stretching or squeezing effects in the radial direction of the recirculation region.
APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION
(2021)
Article
Water Resources
Hyoungchul Park, Jin Hwan Hwang
Summary: A series of laboratory experiments were conducted to understand the role of unsteady coherent motions of turbulent flow in the onset of particle motion. The experiments revealed that the way turbulent eddies initiate grain motion differs under different flow conditions.
ADVANCES IN WATER RESOURCES
(2023)
Article
Physics, Fluids & Plasmas
Marc Rovira, Klas Engvall, Christophe Duwig
Summary: This study presents a modal analysis of counterflowing jets at different velocity ratios using large eddy simulations (LESs) and proper orthogonal decomposition (POD). The research explores the three-dimensional turbulent structure and the origin and development of coherent structures in this flow configuration. Results show that planar two-dimensional (2D) and three-dimensional spectral POD analyses are in close agreement with existing literature.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Engineering, Multidisciplinary
Ziyu Chen, Kaiwen Zhou, Fan Yang, Xin Wen, Yingzheng Liu
Summary: This article proposes and compares two methods for reconstructing temporally resolved flow fields of sweeping jets from sub-Nyquist-rate PIV data, namely least squares (LS) regression and compressive sensing (CS) reconstructions. LS regression relies on high-frequency data from pointwise measurements to estimate temporally resolved POD coefficients, while the CS method calculates temporally resolved coefficients by solving a basic pursuit problem based on sub-Nyquist coefficients.
MEASUREMENT SCIENCE AND TECHNOLOGY
(2021)
Article
Thermodynamics
R. Kapulla, K. H. Manohar, S. Paranjape, D. Paladino
Summary: The study investigates the self-similar behavior of statistical quantities derived from a jet flow using both original data and low-order representations obtained from Proper Orthogonal Decomposition (POD). It is found that statistical properties obtained from low-order representations resemble the shape of the original jet and exhibit asymptotic states with increasing downstream distances. These findings suggest that self-similar behavior is mainly controlled by large-scale vortices, with the exception of axial velocity root-mean-square values.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2021)
Article
Engineering, Civil
Johannes Schobesberger, Dominik Worf, Petr Lichtneger, Sencer Yuecesan, Christoph Hauer, Helmut Habersack, Christine Sindelar
Summary: This study experimentally investigates entrainment events of a single sediment particle on a smooth bed in open channel flow. Tomographic particle tracking velocimetry system and shake the box algorithm were used to determine flow velocities, while proper orthogonal decomposition method was applied to identify motions carrying the most turbulent kinetic energy.
JOURNAL OF HYDRAULIC RESEARCH
(2022)
Article
Mechanics
Oliver T. Schmidt
Summary: The use of multitaper estimates for spectral proper orthogonal decomposition (SPOD) is explored in this study. Multitaper-Welch estimators, using orthogonal tapers for overlapping segments, provide flexible control of resolution, variance, and bias. Compared to the standard algorithm, multitaper-Welch estimators offer lower variance estimates at fixed frequency resolution or higher frequency resolution at similar variance for the same data.
THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS
(2022)
Article
Thermodynamics
Zhu Yang, Victor Castaneda, Guven Ogus, Thomas Holemans, Maarten Vanierschot, Agustin Valera-Medina
Summary: Swirl stabilised flows are commonly used for gas turbine combustion stabilisation. This research focuses on the identification and visualisation of coherent structures in two types of jet flows, namely Open Jet Flow (OJF) and Coanda Jet Flow (CoJF). High speed stereo particle image velocimetry (S-PIV) was used to obtain time-resolved flow fields, and spectral proper orthogonal decomposition was used to identify the coherent structures. The results show that similar precessing coherent flow structures exist in wall attached Coanda swirling flows and swirling jet flows undergoing vortex breakdown.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2023)
Article
Engineering, Mechanical
Yulu Liu, Yuze Wang, Jiahua Li, Yizhou Tao, Xiang Qiu
Summary: The study investigates the dynamics of the vortex structure in a three-dimensional, round counterflow wall jet and explores its generation mechanism. It is found that the vortex ring is formed while the jet is fluttering upwards and the turbulent kinetic energy contribution of the wall-normal component in the recirculation region is particularly significant.
EXPERIMENTS IN FLUIDS
(2022)
Article
Geochemistry & Geophysics
Jiangheng He, Zezong Chen, Chen Zhao, Xi Chen, Yunyu Wei, Chunyang Zhang
Summary: A novel method for wave parameter inversion based on spectral proper orthogonal decomposition (SPOD) is proposed in this study. The method processes the spatial-temporal series of wave orbital velocities using SPOD, removes nonwave contributions, and obtains wave parameters in good agreement with buoy measurements.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2022)
Article
Thermodynamics
Lu Shen, Govind Harikumar, Kai Wang, Fei Duan
Summary: The study investigated the flow behavior near a stack in a hybrid thermoacoustic system using time-resolved particle image velocimetry and found two types of vortices caused by the stack. Proper orthogonal decomposition was applied to illustrate small-scale fluctuations from the main flow structure, with results showing variations in vortical flow structures from cycle to cycle.
EXPERIMENTAL THERMAL AND FLUID SCIENCE
(2021)
Article
Engineering, Aerospace
Zhi Deng, Donglai Gao, Guanbin Chen, Wen-Li Chen
Summary: Experimental investigation on an active-flow control scheme involving leeward slot jet over a circular cylinder showed that the symmetrical jet vortices generated by the slot interact effectively with the sheared layer from the cylinder wall, modifying the flow features in the cylinder wake and transitioning the wake from asymmetric to symmetric. This control technique also significantly reduces Reynolds shear stress and turbulent kinetic energy, demonstrating the potential to manipulate stability characteristics in the flow field behind the cylindrical model.
JOURNAL OF AEROSPACE ENGINEERING
(2021)
Article
Computer Science, Interdisciplinary Applications
N. Silin, G. A. Boroni, J. E. Higham, A. Clausse
Summary: This study presents a methodology to obtain 3D kinematic tomographies of coherent structures from 2D sequences of snapshots. The method synchronizes modal decompositions of multiple independent Particle Image Velocimetry (PIV) scans to produce the 3D results. The method is validated through numerical simulation and applied to experimental measurements, revealing non-trivial 3D features of the coherent structures.
JOURNAL OF VISUALIZATION
(2023)
Article
Environmental Sciences
Hojung You, Rafael O. O. Tinoco
Summary: Underwater obstacles are known to be hotspots for various particulate matters in streams. This study examines the particle behaviors as they pass through a gap between two obstacles, and identifies the impact of gap length on the particle transport. The results show that the transport of particles is influenced by large-scale flow motions, and understanding these patterns can help in effective sampling and monitoring of organic and inorganic particles in aquatic environments.
WATER RESOURCES RESEARCH
(2023)
Article
Agricultural Engineering
Balasubramani Ravindran, Natchimuthu Karmegam, Mukesh Kumar Awasthi, Soon Woong Chang, P. K. Selvi, Ramalingam Balachandar, Sasikala Chinnappan, Nur Izyan Wan Azelee, Ganesh Munuswamy-Ramanujam
Summary: This study investigates the system of co-composting food waste and poultry manure using rice husk biochar. The results show that the addition of biochar improves the characteristics of compost, extends the composting process, reduces gas emissions, and enhances nitrogen retention.
BIORESOURCE TECHNOLOGY
(2022)
Article
Mechanics
S. Das, R. Balachandar, R. M. Barron
Summary: The characteristics of fully developed smooth open channel flow are studied using two-component planar particle image velocimetry. Flow properties are explored by identifying uniform momentum zones and conditional averaging of flow variables. The difference in flow properties between developing and fully developed flow is evaluated.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Civil
Subhadip Das, Ram Balachandar, Ronald M. Barron
Summary: This study investigated the effects of the shear layer generated from light floater boards on flow characteristics. The results showed that the perturbation caused by the floaters altered the mean velocity profiles and resulted in negative shear stress near the free surface. Additionally, the depth of the shear layer penetrating into the flow increased with the increase in perturbation.
JOURNAL OF HYDRAULIC RESEARCH
(2022)
Article
Environmental Sciences
Shanmugam Poornima, Sivasubramanian Manikandan, Vivekanandhan Karthik, Ramalingam Balachandar, Ramasamy Subbaiya, Muthupandian Saravanan, Nguyen Thuy Lan Chi, Arivalagan Pugazhendhi
Summary: The increasing trend of industrialization leads to the release of industrial effluents. Waste water treatment is important for waste disposal and sustainability. Sustainable and energy efficient treatment methods are attractive, but existing technologies have sustainability issues. Conventional and advanced technologies are implemented for wide range of effluents, but secondary sludge generation is unaddressed. Biochar is effective for certain contaminants. Nanotechnology and membrane technology are promising for waste water treatment. Carbon nano structures, nano filters, graphene, and nano magnets are potential candidates.
Article
Materials Science, Multidisciplinary
Subramanian Parvathy, Ganesan Manjula, Ramalingam Balachandar, Ramasamy Subbaiya
Summary: Cerium oxide nanoparticles (CeO2 NPs) were synthesized using Artabotrys hexapetalus leaf extracts, exhibiting a cubic structure and mesh-like morphology. CeO2 NPs showed antibacterial activity and cytotoxic effects on human breast cancer cell line.
Article
Materials Science, Multidisciplinary
Ramalingam Balachandar, Rajendran Navaneethan, Muniyandi Biruntha, Krishna Kumar Ashok Kumar, Muthusamy Govarthanan, Natchimuthu Karmegam
Summary: In this study, silver nanoparticles were synthesized using the ethyl acetate extract of Glochidion candolleanum leaves and showed strong antibacterial activity against Salmonella enterica and Pseudomonas aeruginosa. GC-MS analysis revealed the presence of various bioactive phytochemicals in the extract.
Article
Environmental Sciences
Priscilla Williams, Ram Balachandar, Vesselina Roussinova, Ronald Barron
Summary: This study investigates the mechanism of local scour and the effectiveness of scour countermeasures using particle image velocimetry (PIV) measurements. The results show that a vertical splitter plate reduces the width of scour downstream of the cylinder, while a rectangular collar eliminates scour upstream and causes flow separation.
INTERNATIONAL JOURNAL OF SEDIMENT RESEARCH
(2022)
Article
Mechanics
Kalpana Devi, Prashanth Reddy Hanmaiahgari, Ram Balachandar, Mahendra Reddy Vanteru
Summary: This study evaluates the effects of Reynolds number and submergence ratio on fluid-structure interaction by modifying the free-stream velocity and pipe diameter. The experimental data show that the non-dimensional separation length is linearly varying with the Reynolds number up to a critical value. The profiles of mean velocity, Reynolds shear stresses, correlation coefficient, anisotropy, and turbulent kinetic energy are not affected by the Reynolds number, but are influenced by the submergence ratio.
Review
Environmental Sciences
R. Yedhu Krishnan, S. Manikandan, R. Subbaiya, M. Biruntha, R. Balachandar, N. Karmegam
Summary: Illicit drugs are a group of emerging pollutants that pose a growing global environmental load and ecological risk. Conventional water processing plants struggle to fully remove drugs of abuse from both surface water and wastewater. Despite their detection in surface waterways worldwide, the origins, environmental fate, and ecological repercussions of illicit drugs remain poorly understood. This review examines illicit drug detections in potable water, surface water, and wastewater over the past 15 years to establish a baseline for future research. The most commonly detected drugs with abuse potential include methadone, cocaine, benzoylecgonine, amphetamine, and codeine.
Review
Environmental Sciences
S. Chozhavendhan, G. Karthigadevi, B. Bharathiraja, R. Praveen Kumar, Lata Deso Abo, S. Venkatesa Prabhu, Ramalingam Balachandar, Mani Jayakumar
Summary: This review critically analyzes the biorefinery approaches on anaerobic digestion (AD) process for the production of biogas and digestate, and their direct and indirect utilization. Upgrading or transforming digestate into high valued products can enrich soil nutrients and ensure a safe environment.
ENVIRONMENTAL RESEARCH
(2023)
Article
Mechanics
Ebenezer E. Essel, Ram Balachandar, Mark F. Tachie
Summary: The unsteady wake dynamics of finite wall-mounted cylinders of unequal height and arranged in tandem were studied using TR-PIV. Varying the height of the upstream cylinder, the results showed that the induced upwash from the free end of the upstream cylinder significantly affected the downwash behind the downstream cylinder. The wake dynamics of the downstream cylinder also exhibited a quasi-periodic pumping motion and lock-in anti-symmetric vortex shedding due to the attachment of the shear layers from the upstream cylinder.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Environmental Sciences
R. Ranjith, S. Vignesh, Ramalingam Balachandar, S. Suganthi, V. Raj, Subramaniyan Ramasundaram, J. Kalyana Sundar, Mohd Shkir, Tae Hwan Oh
Summary: In this study, a Bi2O3/g-C3N4 nanocomposite with a direct Z-scheme was obtained using a hydrothermal system. The nanocomposite exhibited excellent photocatalytic degradation performance under visible-light exposure, making it a promising candidate for wastewater treatment.
JOURNAL OF ENVIRONMENTAL MANAGEMENT
(2023)
Article
Mechanics
S. Das, S. Abishek, R. Balachandar, R. M. Barron
Summary: The wake characteristics of wall-mounted finite submerged solid and foam-covered circular cylinders are explored using large-eddy simulation. The study finds that the presence of foam changes the characteristics of recirculation regions and interrupts the formation of large periodic structures.
Review
Engineering, Manufacturing
Corey Klinkhamer, K. Lakshmi Varaha Iyer, Majed Etemadi, Ram Balachandar, Ron Barron
Summary: As electrified vehicles become more popular, the demand for improved cost, reliability, power density, and efficiency of onboard power electronics is increasing. Conventional cooling techniques are reaching their limits, requiring the need for better thermal management solutions. Jet impingement technology has emerged as a promising solution for localized cooling in automotive applications. This article comprehensively reviews the application of jet impingement in cooling power electronics, addressing key flow and heat transfer features, heat sink optimization, enhancement techniques, and limitations to provide an overview of the state-of-the-art.
IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY
(2023)
Article
Thermodynamics
M. Mosavati, R. Barron, R. Balachandar
Summary: In this computational study, the performance of self-oscillating jets for cooling applications is investigated. The flow behavior and heat transfer characteristics of self-oscillating jets are numerically simulated and compared with wall jets and channel flows. Different arrangements of heated devices are also evaluated. The results show that self-oscillating jets provide enhanced heat transfer for devices located away from the central region, while wall jets improve heat transfer around the central region. Channel flow exhibits the lowest heat transfer performance in terms of Nusselt number.
THERMAL SCIENCE AND ENGINEERING PROGRESS
(2023)
