Review
Chemistry, Analytical
Hao Luo, Xiaobao Wang, Xinyan Liu, Xiaoqin Wu, Xiaogang Shi, Qingang Xiong
Summary: This paper reviews the recent advances in multi-scale computational fluid dynamics (CFD) simulations of biomass pyrolysis in fluidized bed reactors. The interconnection among molecular-scale, particle-scale, CFD cell-scale, and reactor-scale are discussed, along with the frameworks of Eulerian-Lagrangian (E-L) and Eulerian multi-fluid model (MFM). The theoretical basis and practical applications of particle-scale models, as well as their coupling with CFD cell-scale and molecular-scale models, are highlighted. The future work to develop reliable and efficient CFD models for simulating biomass pyrolysis in fluidized bed reactors is outlined.
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
(2022)
Article
Metallurgy & Metallurgical Engineering
Xiaomeng Zhang, Stefan Pirker, Mahdi Saeedipour
Summary: The interactions between steel inclusion particles and the steel-slag interface play a critical role in the efficiency of inclusion removal and steel cleanliness. In this study, the three-phase interactions were investigated using the volume of fluid (VOF) method coupled with a dynamic overset mesh. The simulation accurately captured the interface deformation and predicted particle motion driven by capillary force. The wetting condition of the system and the viscosity of the slag were found to be the most influential factors determining particle behavior at the interface. Based on the findings, a criterion for predicting particle behavior was developed. This study provides insights into the interfacial phenomenon during inclusion removal and can improve the accuracy of large-scale simulations in estimating removal efficiency.
STEEL RESEARCH INTERNATIONAL
(2023)
Review
Computer Science, Artificial Intelligence
Dhruvil Panchigar, Kunal Kar, Shashank Shukla, Rhea Mary Mathew, Utkarsh Chadha, Senthil Kumaran Selvaraj
Summary: This review explores the applications of CFD in various scenarios and the logical components required for exemplary computations. It examines the influence of machine learning on design parameters with implemented algorithms, as well as research-based algorithms used in different situations. It also analyzes the advantages, disadvantages, and computing tools of the algorithms.
NEURAL COMPUTING & APPLICATIONS
(2022)
Article
Mechanics
T. Fukada, S. Takeuchi, T. Kajishima
Summary: This study investigates the particle subgrid stress in the volume-average framework for Stokes numbers based on the Kolmogorov time scale up to O(10(2)), introducing a new Stokes number St(R) to extract the effect of fluid velocity fluctuation intensity. The agreement of the particle stress models with the fully resolved particle stress is examined as a function of St(R), showing the highest degree for the fluid residual stress model over a small St(R) range. Investigation is also done on the effects of St(R), St(K), averaging volume size, and Reynolds number on the model coefficients based on the fully resolved particle stress and its models.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Chemical
Kirill Mikhaylov, Stelios Rigopoulos, George Papadakis
Summary: The study combines reduced order modeling and system identification to reconstruct the temporal evolution of large-scale vortical structures behind the blades of a Rushton impeller. The results demonstrate that even using the velocity time signal from a single sensor point, the first pair of modes can be reconstructed well. Increasing the number of sensor points improves accuracy and stability, leading to better reconstruction of the second pair of POD modes. The estimator derived at Reynolds number 600 shows robustness when applied to flows at Reynolds numbers 500 and 700.
Article
Pharmacology & Pharmacy
Azadeh A. T. Borojeni, Wanjun Gu, Bahman Asgharian, Owen Price, Andrew P. Kuprat, Rajesh K. Singh, Sean Colby, Richard A. Corley, Chantal Darquenne
Summary: The extrathoracic oral airway acts as a barrier for pharmaceutical aerosols and introduces variability in lung deposition. Computational fluid dynamics was used to predict deposition of 1-30 μm particles in CT-based models of adult oral airways. Results showed large intersubject variability in oral deposition, with nebulizers delivering >75% of inhaled aerosol to intrathoracic lungs in most subjects compared to only about half with DPI use. Oral deposition efficiency did not differ significantly between inspiration and expiration, but subregional deposition showed different patterns between the two breathing phases. Incorporating upper airway morphological variation is crucial for accurate predictions of aerosol deposition in the lung.
Article
Computer Science, Interdisciplinary Applications
Cristian C. Lalescu, Berenger Bramas, Markus Rampp, Michael Wilczek
Summary: The study introduces a particle tracking algorithm for large-scale parallel pseudo-spectral simulations of turbulence that can handle billions of tracer particles efficiently. By using a task-based method, resource utilization is improved and computational costs of particle tracking are reduced.
COMPUTER PHYSICS COMMUNICATIONS
(2022)
Article
Engineering, Environmental
Olav R. Hansen, Eirik S. Hansen
Summary: This article describes the large-scale LH2 release tests commissioned by the Norwegian Public Roads Administration to study the dispersion and explosion properties of liquid hydrogen (LH2) both indoor and outdoor. The study aims to better understand the experiments and demonstrate that LH2 safety assessments can be accurately simulated and predicted.
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
(2023)
Article
Mechanics
G. Cui, I. Ruhman, I. Jacobi
Summary: In this study, large-scale inertial particle clustering in a turbulent boundary layer was investigated using two-color particle-image velocimetry and particle-tracking velocimetry measurements. Voronoi tessellation and spatial wavelet transform techniques were applied to detect anisotropic, large-scale particle clusters, and their hierarchical structures were identified. The results showed that the large-scale clusters were composed of smaller clusters of varying degrees of isotropy. Furthermore, larger clusters exhibited faster particle convection speeds.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Civil
Samuel Stevens, David Rush
Summary: Informal settlements are susceptible to significant fire spread caused by external venting flame (EVF). The accuracy of existing empirical models for flame dimensions in informal settlement fire spread scenarios is questioned in this paper. Numerical verification is conducted to identify discrepancies in the theory underlying current flame dimension models. New empirical correlations for EVF height and length are proposed, which better capture the characteristics observed in experiments, although further data input is needed.
FIRE SAFETY JOURNAL
(2023)
Article
Geography, Physical
Jason Duguay, Pascale Biron, Thomas Buffin-Belanger
Summary: Researchers analyzed aerial video and numerical simulation results, finding different types of turbulent structures form at river confluences, including vertically orientated vortices, secondary flow helical cells, and streamwise-orientated vortices. These turbulent structures interact with each other and play significant roles in the mixing processes.
EARTH SURFACE PROCESSES AND LANDFORMS
(2022)
Article
Energy & Fuels
Mustafa Metin Cam, Hakan Serhad Soyhan, Mansour Al Qubeissi, Cenk Celik
Summary: The design of energy efficient engineering systems is crucial for sustainable operation. This study focuses on optimizing the bell-type primary air nozzle used in CFB boilers through CFD simulations. By changing the nozzle geometry, pressure drop can be decreased and flow uniformity can be improved, resulting in energy savings and improved boiler operation.
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
M. A. Gorokhovski, S. K. Oruganti
Summary: The study introduces a Lagrangian stochastic model for particle motion and evaporation in large-eddy simulations, addressing small-scale intermittency effects. The model considers the norm and direction of the droplet sub-filtered acceleration, with increasing Reynolds numbers leading to stronger fluctuations in the energy dissipation rate. Validated in simulations of high-speed sprays, the models accurately predict experimental data with weaker sensitivity to grid spacing, showcasing the significant impact of turbulence on vaporization rates.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Chemical
Zhenzhen Hu, Ruiping Ma, Yusheng Wang, Miao Lou, Minjie Gong, Botao Wang, Guoxi Zheng, Jingliang Dong, Ya Zhang
Summary: There is a lack of studies on the pollen transport and deposition in children nasal airways, especially the regional deposition doses, which hinders the precise application of pollen blockers and nasal administration. In this study, computational fluid particle dynamics modeling was used to analyze the deposition pattern of Artemisia pollen in the upper airway of children with adenoid hypertrophy (AH), and the effects of respiratory flow rate and pollen density on the deposition distribution. The findings suggest notable differences in deposition hotspots and deposition patterns between children and adults, with dry Artemisia pollen posing a higher risk of entering the lower respiratory airways in children.
JOURNAL OF AEROSOL SCIENCE
(2023)