Article
Mechanics
Chuong V. Tran, Xinwei Yu, David G. Dritschel
Summary: Incompressible fluid flows are characterized by high correlations between velocity and pressure, as well as between vorticity and pressure. This correlation plays a significant role in maintaining regularity in Navier-Stokes flows. The study suggests that as long as global pressure minimum (or minima) and velocity maximum (or maxima) are mutually exclusive, regularity is likely to persist.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Shang-Gui Cai, Johan Degrigny, Jean-Francois Boussuge, Pierre Sagaut
Summary: An improved coupling method of immersed boundary method and turbulence wall models on Cartesian grids is proposed to generate smooth wall surface pressure and skin friction at high Reynolds numbers. Various modifications are presented to enhance the near wall solution, and the validity of the method is demonstrated through numerical benchmark tests.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Mathematics, Applied
Yanqing Wang, Yulin Ye
Summary: In this paper, an energy conservation criterion is derived for weak solutions of both the incompressible and compressible Navier-Stokes equations. The criterion is based on a combination of velocity and its gradient. For the incompressible case, it extends known results on periodic domain, including the famous Lions' energy conservation criterion. For the compressible case, it improves recent results and extends criteria for energy conservation from incompressible to compressible flow.
MATHEMATICAL METHODS IN THE APPLIED SCIENCES
(2023)
Article
Engineering, Multidisciplinary
Xueying Zhang, Yangjiong Wu
Summary: This paper proposes a high resolution strategy for the localized method of approximate particular solutions (LMAPS). The strategy aims to improve the accuracy and stability of numerical calculation by selecting upwind interpolation templates. Numerical results demonstrate that the proposed high-resolution LMAPS is effective and accurate, especially for solving the Navier-Stokes equations with high Reynolds number.
ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS
(2024)
Article
Mathematics, Applied
Qiang Ma, Jianxin Lv, Lin Bi
Summary: This paper introduces a linear stability equation based on the Boltzmann equation and establishes the relationship between small perturbations and macroscopic variables. The numerical solutions of the linear stability equations based on the Boltzmann equation and the Navier-Stokes equations are the same under the continuum assumption, providing a theoretical foundation for stability research.
COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION
(2024)
Article
Multidisciplinary Sciences
Koji Ohkitani
Summary: This paper discusses non-Gaussian self-similar solutions to the Navier-Stokes equations and provides detailed mathematical derivations. It also explores the application of self-similar solutions to study more general solutions, using the source-type self-similar solution as a basis.
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2022)
Article
Computer Science, Interdisciplinary Applications
Xinyi L. D. Huang, Naman Jain, Mahdi Abkar, Robert F. Kunz, Xiang I. A. Yang
Summary: The study addresses the challenge of determining if model improvement based on calibration data generalizes to other flow conditions by using global epistemic Uncertainty Quantification (UQ). The global epistemic UQ method evaluates potential improvements in terms of effectiveness and inconsistency, allowing for the classification of improvements into four quadrants to determine if they would generalize. The study successfully applies the global epistemic UQ to predict the growth of a stratified shear layer and demonstrates the model's ability to generalize under certain conditions.
COMPUTERS & FLUIDS
(2021)
Article
Mathematics, Applied
Juan Vicente Gutierrez-Santacreu, Marko Antonio Rojas-Medar
Summary: The Navier-Stokes-alpha equations are a type of LES models that aim to capture the influence of small scales on large ones without calculating the entire flow range. The parameter α represents the smallest resolvable scale by the model. When α=0, the classical Navier-Stokes equations for viscous, incompressible, Newtonian fluids are recovered. These equations can also be seen as a regularization of the Navier-Stokes equations, where α stands for the regularization parameter.
PHYSICA D-NONLINEAR PHENOMENA
(2023)
Article
Mechanics
Y. Marchenay, F. Chedevergne, M. Olazabal Loume
Summary: A new modeling strategy is proposed to predict the combined effects of roughness and blowing boundary conditions. Analysis of experimental data reveals deficiencies in existing roughness corrections when predicting the effect of blowing in the presence of surface roughness.
Article
Thermodynamics
Yang Zheng, Cheng Xu, Zheng Xinghua, Chen Haisheng
Summary: The paper presents a set of new equations SCF-RANS equations to describe turbulent flow and heat transfer of supercritical fluid, taking into account the fluctuation of thermal physical properties. Various model methods for the new correlation term have been discussed for closing the equations, providing reference information for these new correlations. The SCF-RANS equations not only offer a formulation specific to supercritical fluid flow and heat transfer, but also represent the most sophisticated form of the RANS equations with consideration of all physical properties as variables.
JOURNAL OF THERMAL SCIENCE
(2021)
Article
Biochemical Research Methods
Mostafa Jafari, Mostafa Jamshidian, Shayan Habibi
Summary: In this study, the Reynolds-Averaged Navier-Stokes approach with the k-epsilon closure model is used to simulate direct Solid-Phase Micro-Extraction computationally for the first time. Experimental data is also collected to support the numerical simulations. The results indicate that increasing the stirring rate, changing the fiber's location, and implementing a periodic stirring pattern can significantly decrease the extraction time of SPME.
JOURNAL OF CHROMATOGRAPHY A
(2022)
Article
Mathematics, Interdisciplinary Applications
Mingshuo Liu, Lijun Zhang, Yong Fang, Yong Zhang, Huanhe Dong
Summary: The symmetries of hydrodynamic equations with complex nonlinear terms and strong coupling are investigated. Lie symmetry analysis is applied to the nonlinear Euler, Navier-Stokes, and magnetohydrodynamic equations using Lie group of transformations. Similarity reductions and exact solutions generated from symmetry transformations are provided. Conservation laws of the equations are successfully constructed, enabling a scientific description of hydrodynamic systems.
CHAOS SOLITONS & FRACTALS
(2023)
Article
Mathematics, Applied
Elizabeth Carlson, Adam Larios
Summary: The well-posedness of the formal sensitivity equations with respect to viscosity for the 2D incompressible Navier-Stokes equations is rigorously proven in this study, showing convergence of difference quotients to the unique solution of the sensitivity equations. This proof method provides uniform bounds on difference quotients, indicating stable behavior of parameter recovery algorithms as the system evolves. Additionally, the analysis can be extended to the sensitivity of the 2D Euler equations to viscous regularization, marking a significant development in understanding the global existence and uniqueness of sensitivity equations in fluid dynamics.
JOURNAL OF NONLINEAR SCIENCE
(2021)
Article
Mathematics
Maria Colombo, Silja Haffter
Summary: The study investigates solutions of the Navier-Stokes equation with fractional dissipation, showing the existence of a unique global smooth solution under certain conditions. This is related to a new stability result on smooth solutions of the Navier-Stokes equations with fractional dissipation.
JOURNAL OF DIFFERENTIAL EQUATIONS
(2021)
Article
Mathematics, Applied
Senming Chen
Summary: This article studies the energy conservation property of the weak solution of the 3D Euler-Navier-Stokes system. Two sufficient conditions are provided to ensure the conservation of total energy, including the initial energy. A variant method is adopted to deal with the density of Euler flows and velocity of Navier-Stokes fluid due to the coupling structure between the inhomogeneous Euler equation and the incompressible Navier-Stokes system.
MATHEMATICAL METHODS IN THE APPLIED SCIENCES
(2023)
Article
Energy & Fuels
Arash Nemati, Jiun Cai Ong, Kar Mun Pang, Stefan Mayer, Jens Honore Walther
Summary: The study shows that further methane injection at low load conditions in dual-fuel marine engines can achieve better combustion efficiency, while at high load conditions, there is less NO formation. Adjusting the timing of pilot fuel injection can affect combustion quality and emission formation.
Letter
Multidisciplinary Sciences
Sally P. Leys, Eugueni Matveev, Pablo Aragones Suarez, Amanda S. Kahn, Seyed Saeed Asadzadeh, Thomas Kiorboe, Poul S. Larsen, Jens H. Walther, Gitai Yahel
Article
Mechanics
Yunfeng Ding, Jens Honore Walther, Yanlin Shao
Summary: A nonlinear piston-mode fluid resonance in the gap formed by two identical fixed barges in close proximity is investigated using a two-dimensional fully nonlinear numerical wave tank. The results show that under the action of shallow-water waves, strong higher-order resonances occur in the gap, resulting in significant higher-harmonic responses. Unlike what linear diffraction theory predicts, the gap response behaves differently under long cnoidal waves, and the higher harmonics generally have larger phase differences to the incident-wave components.
Article
Engineering, Chemical
Sima Majidi, Hamid Erfan-Niya, Jafar Azamat, Eduardo R. Cruz-Chu, Jens Honore Walther
Summary: The performance of carbon nitride (C2N) for separating Cu2+ and Hg2+ heavy metal ions from water was studied using molecular dynamic simulations. The high porosity of the C2N nanosheet and the nitrogen atoms at the edge of the pores contribute to its efficiency for water purification. The permeability of Cu2+ ions through C2N is 2.5 times higher than that of Hg2+, and the hydration shell of the cations causes an energy barrier for ion passage. The density of cations and water molecules, as well as the hydrogen bonds between water molecules, were analyzed, demonstrating the selectivity performance and high permeability of C2N for heavy metal removal.
SEPARATION AND PURIFICATION TECHNOLOGY
(2022)
Article
Physics, Fluids & Plasmas
S. S. Asadzadeh, J. H. Walther, A. Andersen, T. Kiorboe
Summary: The flagella of unicellular flagellated micro-organisms play an important role in aquatic food webs by allowing them to swim and generate feeding currents. Predatory flagellates have hairs on their flagella that reverse the thrust direction compared to a smooth flagella. Previous studies have attributed this reversal to drag-based thrust of individual hairs, neglecting their hydrodynamic interactions. However, this study shows that hydrodynamic interactions are key to thrust generation and reversal in hairy flagellates, making their hydrodynamics fundamentally different from those of smooth flagella. The curvature of the flagella is found to play a significant role in thrust generation, with strongly curved flagellar waveforms being optimal. These findings provide a basis for understanding the diverse flagellar architectures and feeding modes of predatory flagellates.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Thermodynamics
Jiun Cai Ong, Yan Zhang, Shijie Xu, Jens Honore Walther, Xue-Song Bai, Kar Mun Pang
Summary: The present study uses large-eddy simulations (LES) to investigate the ignition and stabilization mechanisms of ECN Spray A flame under different injection pressures and ambient temperatures. The numerical model is validated against experimental data and the role of auto-ignition in flame stabilization is found to be crucial.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Chemistry, Applied
Sima Majidi, Hamid Erfan-Niya, Jafar Azamat, Soroush Ziaei, Eduardo R. Cruz-Chu, Jens Honore Walther
Summary: The global demand for clean and potable water is increasing due to population growth and pollution. Water contamination is a global problem that needs to be investigated for proper strategies to improve water quality and reduce water scarcity. Membrane technologies for water purification show promising results. This review discusses the use of molecular dynamics (MD) simulations to evaluate the performance of membrane-based water purification systems. The article also provides insights into recent developments and limitations of MD simulations in wastewater treatment using membranes.
SEPARATION AND PURIFICATION REVIEWS
(2023)
Article
Biochemical Research Methods
Sima Majidi, Hamid Erfan-Niya, Jafar Azamat, Eduardo R. Cruz-Chu, Jens Honore Walther
Summary: In this study, molecular dynamics simulation is used to investigate the effectiveness of graphdiyne nanosheet in separating nitrate ions from water. The results show that the fine regulation of hydrostatic pressure allows for efficient water flow and high water permeability, making graphdiyne a suitable membrane for nitrate separation.
JOURNAL OF MOLECULAR GRAPHICS & MODELLING
(2023)
Article
Chemistry, Physical
Elton Oyarzua, Jens H. H. Walther, Harvey A. A. Zambrano
Summary: The study introduces a graphene-based thermal nanopump that can produce controlled and continuous liquid flow in nanoslit channels by utilizing thermal gradients. Large-scale molecular dynamics simulations were conducted to investigate the performance of this thermal nanopump. The results show that water flow rates increase due to larger ripple fluctuations on the graphene layers as higher thermal gradients are applied, and the efficiency of the pump can be enhanced by modifying the wettability of the channel walls.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Engineering, Chemical
Seyed Heydar Rajaee Shooshtari, Jens Honore Walther, Chuang Wen
Summary: This paper presents a novel approach using computational fluid dynamics (CFD) and genetic algorithm to provide new equations for normal shock waves. The proposed model shows more accurate predictions for shock position compared to the traditional theoretical model. It can be used as an accurate and efficient tool for shock position prediction and nozzle design.
SEPARATION AND PURIFICATION TECHNOLOGY
(2023)
Article
Energy & Fuels
Ji Zhang, Zhi Cao, Sheng Huang, Xiaohui Huang, Yu Han, Chuang Wen, Jens Honore Walther, Yan Yang
Summary: In this study, a novel combination of branch-structured fins and Al2O3 nanoparticles was proposed to enhance the performance of a phase change material (PCM) in a triple-tube heat exchanger. A mathematical model was developed and validated based on experimental results, considering thermal conduction, Brownian motion of nanoparticles, and natural convection in the liquid PCM. The results showed that both nanoparticles and metal fins significantly improved the solidification behavior, with metal fins having a greater impact compared to nanoparticles.
Article
Energy & Fuels
Min Zhang, Jiun Cai Ong, Kar Mun Pang, Shijie Xu, Yan Zhang, Arash Nemati, Xue-Song Bai, Jens Honore Walther
Summary: The present study uses large eddy simulation to investigate combustion recession for the Engine Combustion Network Spray A flame under different ambient temperatures and injection pressures. The numerical results accurately capture the different combustion recession phenomena. The combustion recession is mainly controlled by the auto-ignition process at a higher ambient temperature, while at a lower ambient temperature, the local temperature within the fuel-rich region is not high enough to promote high-temperature ignition.
Article
Energy & Fuels
Arash Nemati, Jiun Cai Ong, Min Zhang, Jens Honore Walther
Summary: The auto-ignition process of micro-pilot diesel in premixed dual-fuel combustion was studied using large eddy simulation. It was found that the inhomogeneity in temperature has a more significant influence on the ignition delay time (IDT) than methane inhomogeneity. The inhomogeneity pockets of temperature advance the first-stage and second-stage ignition. This study is important for improving engine performance and reducing exhaust emissions.
Article
Mechanics
Diego Becerra, Andres Cordoba, Jens H. Walther, Harvey A. Zambrano
Summary: Through atomic-level simulations, it is found that graphene coating significantly enhances water flow in nanochannels compared to hexagonal boron nitride (hBN) coating. The natural undulations of graphene coating further enhance water flow.
Article
Engineering, Ocean
Nicolai Arent Quist, Rasmus Haurum Christensen, Henrik Mikkelsen, Jens Honore Walther
Summary: This study verifies and validates a full-scale self-propulsion CFD model that incorporates hull roughness and welding seams. The results show the importance of measuring hull roughness for accurate performance calculations and the increase in resistance caused by welding seam modeling.
APPLIED OCEAN RESEARCH
(2023)
Article
Engineering, Mechanical
Busra Duran, Jerome Cavoret, David Philippon, Fabrice Ville, Arnaud Ruellan, Frank Berens
Summary: This study analyzes the changes in the physicochemical properties and tribological performances of gear transmission oils during field operation, finding differences from traditional engine oils.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Baocheng Liu, Hongsheng Chen, Jun Zhou, Jing Wang, Wenxian Wang, Xiaochun Chen, Sanxiao Xi
Summary: This study used fast hot pressing sintering to fabricate WC/AlCoCrFeNi2.1 metal matrix composites (MMCs). It was found that the addition of reinforced particles increased the microhardness, nanoindentation and wear resistance of the MMCs. During frictional processes, an oxide film formed, providing material protection, enhancing stability and reducing friction-induced losses.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Pradip Kumar Verma, Alok Singh
Summary: This study investigates the mechanical properties and wear resistance of CoMoMnNiV high entropy alloy reinforced aluminium matrix composite processed through stir-squeeze casting assisted with an ultrasonic transducer. The results show significant improvements in mechanical properties and wear resistance, with the composite containing 8 wt% HEA demonstrating the highest resistance to wear. Optical microscopy, SEM, and an optical profilometer were used for a thorough examination of the microstructure and worn surface.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Zhenghai Yang, Yingjian Song, Jinlong Jiao, Wenbo Li, Bao Shangguan, Yongzhen Zhang
Summary: This study investigated the friction, wear properties, and current-carrying properties of copper-graphite composites paired with brass C28000. The results showed that the current-carrying properties of the composite materials were excellent, but their wear rate was the main limiting factor. Furthermore, an increase in the thickness of the graphite layer led to an improvement in the uniformity of damage.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Moustafa Mahmoud Yousry Zaghloul, Karen Steel, Martin Veidt, Michael T. Heitzmann
Summary: This research evaluates and compares the impact of different material types on the tribological characteristics of Polyamide 6 composites, and finds that glass fiber-reinforced Polyamide 6 exhibits better friction and wear performance under high-pressure velocity factors.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Shaoqing Qin, Lida Zhu
Summary: In this paper, the surface and subsurface damage of laser assisted grinding CrCoNi medium entropy alloys were investigated using molecular dynamics simulations. The results showed that the application of laser energy can reduce cutting forces and minimize subsurface damage.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Kaikui Zheng, Youxi Lin, Tingzheng Lai, Chenghui Gao, Ming Liu, Zhiying Ren
Summary: The study investigated the use of waste foundry resin-bonded sand as a substitute for copper in resin-based brake material. It found that the waste sand was more favorable for improving the overall friction and wear properties of the material compared to copper. Waste sand benefited the material by forming a friction layer, leading to increased friction coefficient and stability. Brake material with 10-15% waste sand showed excellent heat-fade resistance.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Dayang Li, Fanhao Zhou, Yutong Gao, Kun Yang, Huimin Gao
Summary: This article introduces a continuous prediction model based on deep learning for predicting the power output of steam turbines. The model uses long short term memory (LSTM) method to develop a trend prediction model and optimizes the prediction model through feature selection method. Experimental results show that the model outperforms other models in terms of prediction performance.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Tomohiro Toyoda, Ryo Yasuike, Toshihiro Noda
Summary: In this study, a elasto-plastic constitutive model of friction incorporating the concept of superloading surface was developed based on the subloading friction model. The proposed model achieves a smooth transition of friction by describing the evolution rule of structure, treating the state with static friction coefficient larger than kinetic friction coefficient as the bulkiness of structure. The positive definiteness of the plastic multiplier, loading condition, and material parameters were derived, and the validity of the proposed model in accordance with the subloading-friction model was confirmed through a stick-slip simulation of a mass-spring system.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
P. Balaji, B. Surya Rajan, K. Sathickbasha, P. Baskara Sethupathi, Deviga Magadevan
Summary: This study emphasizes the importance of using a variety of solid lubricants with different oxidation temperature regimes to enhance the tribological performance of brake pads.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Jian Ma, Yancong Liu, Javad Mostaghimi, Na Zhang
Summary: This paper investigates the influence of preparation strategies on the lubrication properties of surface textures. Three laser scanning strategies are proposed to achieve a sinusoidal textured surface, and the evolution of surface structure and chemical composition is discussed. The findings show that ridge structures enhance anti-wear properties but also increase the friction coefficient. However, the oil cover preparation method prevents the formation of ridges and improves wettability.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Mohammad Roostaei, Arvin Taghizadeh Tabrizi, Hossein Aghajani
Summary: In this research, the Al2O3/MoS2 nanocomposite coating layer was successfully applied on the surface of Ti-6Al-4 V alloy. The relation between the surface characteristics and wear resistance of the coating was studied using atomic force microscopy analysis and pin-on-disk wear test method. The results showed that the nanocomposite coating significantly reduced the wear rate and provided an equation to calculate the Lancaster coefficient.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Musa Bilgin, Sener Karabulut, Halil Karakoc, Yunus Kayir, Murat Sarikaya
Summary: This study investigates various methods to improve the machinability efficiency of Inconel 718 alloy while considering their effect on microstructural properties. The results show that hot+PMQL, hot+SiCNMQL, and hot+Al2O3-NMQL contribute significantly to the improvement of machinability characteristics. The EBSD analysis also reveals that a limited area is affected by heat in the hot machining environment and that the removal of the heated layer during milling process helps preserve the microstructure.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Q. Gao, Y. Fan, Y. G. Wu, J. L. Liu, J. Wang, L. Li
Summary: Fretting wear significantly affects the hysteresis behavior of the contact surface and leads to joint degradation. This study investigates the influence of harmonic normal force on the evolution of interface morphology and contact parameters with fretting wear. The results show that the harmonic normal force can significantly influence the hysteresis loop and the energy dissipation distribution on the contact surface.
TRIBOLOGY INTERNATIONAL
(2024)
Article
Engineering, Mechanical
Benjamin Weiland, Floriane Leclinche, Anis Kaci, Brigitte Camillieri, Betty Lemaire-Semail, Marie -Ange Bueno
Summary: This study presents a systematic approach to generating control signals for a tactile simulator that simulate the touch of textile fabrics. By using a friction modulation tactile surface and acquiring forces from real surfaces with artificial finger mimicking fingerprints, control signals are generated and processed in the frequency domain before sending them to the tactile stimulator. The study focuses on the potential benefits of incorporating fingerprint information in fabric simulations to achieve a more realistic tactile perception. A sensory analysis with 36 participants using the generated control signals showed better discrimination without fingerprint information.
TRIBOLOGY INTERNATIONAL
(2024)
