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Postoperative virtual pressure difference as a new index for the risk assessment of liver resection from biomechanical analysis

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COMPUTERS IN BIOLOGY AND MEDICINE 2023年 157卷 106725-106725页

作者： Song, Hongqing Li, Xiaofan Huang, Hao Xie, Chiyu Qu, Wei Univ Sci & Technol Beijing Beijing 100083 Peoples R China Capital Med Univ Beijing Friendship Hosp Dept Gen Surg Liver Transplantat Sect Beijing 100050 Peoples R China 95 Yong Rd Beijing 100050 Peoples R China

In the realm of hepatectomy, traditional methods for postoperative risk assessment are limited in their ability to provide comprehensive and intuitive evaluations of donor risk. To address this issue, there is a need for the development of more multifaceted indicators to assess the risk in hepatectomy donors. In an effort to improve postoperative risk assessments, a computational fluid dynamics (CFD) model was developed to analyze blood flow properties, such as streamlines, vorticity, and pressure, in 10 eligible donors. By comparing the correlation between vorticity, maximum velocity, postoperative virtual pressure difference and TB, a novel index - post-operative virtual pressure difference -was proposed from a biomechanical perspective. This index demonstrated a high correlation (0.98) with total bilirubin values. Donors who underwent right liver lobe resections had greater pressure gradient values than those who underwent left liver lobe resected donors due to the denser streamlines and higher velocity and vorticity values of the former group. Compared with traditional medical methods, the biofluid dynamic analysis using CFD offers advantages in terms of accuracy, efficiency, and intuition.

关键词： Postoperative risk assessment Liver lobe transplantation Biofluid dynamics computational fluid dynamics simulation

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CFD Methodology for an Underhood Analysis towards the Optimum Fan Position in a Compact Off-Road Machine

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ENERGIES 2023年第11期16卷 4369-4369页

作者： Ferrari, Cristian Beccati, Nicolo Pedrielli, Francesca CNR Natl Res Council Italy Inst Sci & Technol Sustainable Energy & Mobil STEMS Via Canal Bianco 28 I-44124 Ferrara Italy

A compact off-road machine tends to have a compact engine structure, which may result in small clearances between the main engine, the cooling system, and the radiator. In the design of its cooling system, the heat exchanger, fan, and conveyor are normally chosen based on their fixed operating point. Unfortunately, these machines work in variable conditions and the performance of each component is different when they are working as a whole under the hood. The aim of this work is to optimize the position of these components through a parametric analysis of some variables, using the computational fluid dynamics technique. The air flows are analyzed in order to show the pressure waves created by the air moved by the fan blades, showing how the fluid interacts with the engine. The results show that optimizing this installation can increase the efficiency of the fan by 10% and reduce the noise emitted by 13 dB. These results should sensitize designers to use CFD analyses, not for a single component, but for the entire system. The methodology shown can be applied for the better design of cooling systems, mainly in off-road vehicles that have noise emission problems.

关键词： underhood analysis axial fan optimum design noise emission computational fluid dynamics simulation

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Design and simulation of a conformal optical window pair by the quasi-quantitative Schlieren measurement in a cylindrical isolator

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OPTICAL ENGINEERING 2023年第3期62卷 035107-035107页

作者： Ou, Yang Dai, Yifan Chen, Shanyong Fan, Xiaoqiang Xiong, Bing Xu, Shangcheng Hu, Hao Xiong, Yupeng Yan, Yuepeng Du, Chunyang Peng, Wenxiang Guan, Chaoliang Natl Univ Def Technol Coll Intelligent Sci Changsha Peoples R China Natl Univ Def Technol Lab Sci & Technol Integrated Logist Support Changsha Peoples R China HuNan Key Lab Ultraprecis Machining Technol Changsha Peoples R China Natl Univ Def Technol Coll Aerosp Sci & Engn Changsha Peoples R China

To realize the quasi-quantitative Schlieren measurement of the shock train structure across the cylindrical isolator in the supersonic flow field, based on the theory of Schlieren measurement and light transmission, we propose the design scheme of conformal windows and discuss the machining feasibility with the window's parameters. The relationship between the Schlieren imaging effect, the deflection of parallel light in the Schlieren apparatus, and the conformal optical window aberrations was researched, putting forward the optical simulation model of the conformal optical windows and the quasi-quantitative Schlieren measurement. Moreover, considering the actual wind tunnel test conditions, under the speed of Mach 2 at the isolator's inlet, the distortion brought by conformal optical windows in the Schlieren observation region was simulated by the computational fluid dynamics method. Finally, the image correction algorithm for the distorted picture caused by the conformal windows was presented, and the quasi-quantitative Schlieren measurement through the conformal optical window pair was conducted for the experimental verification. The results reveal the quasi-quantitative Schlieren measurement effect across the high-precision conformal optical window pair of the cylindrical isolator, providing guidance on maintaining the balance between the manufacturing feasibility and the observation performance of conformal windows. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

关键词： optical imaging conformal window cylindrical isolator Schlieren measurement computational fluid dynamics simulation

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Numerical investigation of effects of trees on cross-ventilation of an isolated building

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JOURNAL OF BUILDING ENGINEERING 2023年 73卷

作者： Zhang, Xuelin Buddhika, J. W. G. Wang, Jiayao Weerasuriya, A. U. Tse, K. T. Sun Yat Sen Univ Sch Atmospher Sci Southern Marine Sci & Engn Guangdong Lab Zhuhai Zhuhai Peoples R China Sun Yat Sen Univ Key Lab Trop Atmosphere Ocean Syst Minist Educ Zhuhai 519000 Peoples R China Sun Yat Sen Univ Guangdong Prov Key Lab Climate Change & Nat Disast Zhuhai Peoples R China Univ Moratuwa Dept Civil Engn Katubedda Sri Lanka Hong Kong Univ Sci & Technol Dept Civil & Environm Engn Kowloon Hong Kong Peoples R China Hong Kong Metropolitan Univ Sch Sci & Technol Dept Construct & Qual Management Ho Man Tin Hong Kong Peoples R China

Trees are often planted next to buildings for shade, evapotranspiration cooling, and as windbreaks. As windbreaks, trees slow down wind, consequently reducing the natural ventilation of the buildings that they shield. This reduction in natural ventilation has such parameters as the trees' locations, geometry (height (h), width (w), thickness (t)), foliage (e.g., shape and thickness), leaf area density (LAD), and leaf drag coefficient (Cd). This study investigated how these parameters impact the cross ventilation of a generic building (5 m x 5 m x 5 m) exposed to an atmospheric boundary layer wind flow using Reynolds Average Navier-Stokes (RANS)-based computational fluid dynamics (CFD) simulations. Using source terms, trees were modeled as a porous medium, which decelerates wind speed and increases turbulence generation and dissipation. The effects of trees on cross ventilation were quantified by calculating ventilation rate reduction and conducting a local sensitivity analysis (LSA). As the LSA revealed, LAD, h, and Cd were the three parameters with the most influence on reducing cross-ventilation rates, which are strongly and linearly dependent on LAD and Cd. Cross ventilation rates vary with w and d nonlinearly despite their minor impact. Moreover, conical or oval foliage with a narrow upper part affects cross ventilation less than cuboidal or V-shaped foliage with a wider upper section. This study recommends trees shorter than 0.25H, and thinner than 0.168H with sparse and conical foliage to be planted upstream of a building, but not within 1H-3.5H, to minimize adverse effects on cross ventilation.

关键词： Cross -ventilation Trees computational fluid dynamics simulation Local sensitivity analysis

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Accuracy of CFD simulations in urban aerodynamics and microclimate: Progress and challenges

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BUILDING AND ENVIRONMENT 2023年第1期243卷

作者： Tominaga, Yoshihide Wang, Liangzhu (Leon) Zhai, Zhiqiang (John) Stathopoulos, Ted Niigata Inst Technol Wind & Fluid Engn Res Ctr Niigata Japan Concordia Univ Dept Bldg Civil & Environm Engn Montreal PQ Canada Univ Colorado Dept Civil Environm & Architectural Engn Boulder CO USA 1719 Fujihashi Kashiwazaki Niigata 9451195 Japan

This review outlines historical and recent research progress on the accuracy of computational fluid dynamics (CFD) simulations of urban aerodynamics and microclimates and clarifies future research directions and significant challenges for accuracy and reliability using CFD in this field. First, the development and accepted concepts of verification and validation (V&V) and uncertainty quantification (UQ) in general computer simulations and CFD are reviewed. Subsequently, progress made in V&V and UQ for urban aerodynamics and microclimate CFD simulations is described. The required or acceptable accuracy in this field has been discussed in several studies;however, challenges specific to applying CFD in this area should be recognized considering that the target phenomenon in urban aerodynamics and microclimates is complex. In addition, constructing a conceptual model is challenging and has many uncertainties. Furthermore, this field is characterized by significant spatial distributions of physical quantities, such as wind speed, temperature, and other scalar variables;thus, specific validation metrics and multilateral methods, including a conventional profile comparison, should be used. Therefore, the V&V and UQ processes should be implemented thoroughly, considering the characteristics of urban aerodynamics and microclimates. Discussions presented in this paper are of utmost importance and very timely in terms of simulation quality controls, especially during this new era of machine learning and artificial intelligence-based models that started being applied to urban aerodynamics and microclimate predictions.

关键词： computational fluid dynamics simulation Urban aerodynamics Urban microclimate Verification and validation Uncertainty quantification

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Insights into Mn loaded carbon-silica-membrane based catalytic ozonation process for efficient wastewater treatment: Performance and mechanism

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CHEMICAL ENGINEERING JOURNAL 2023年 475卷

作者： Chen, Shuning Ren, Tengfei Zhou, Zuoyong Lu, Kechao Huang, Xia Zhang, Xiaoyuan Tsinghua Univ Sch Environm State Key Joint Lab Environm Simulat & Pollut Cont Beijing 100084 Peoples R China

Heterogeneous catalytic ozonation (HCO) is a promising technology for advanced wastewater treatment, and developing catalysts with both high catalytic activity and easy recycling capability is challenging but essential. In this work, easily separable Mn loaded carbon-silica-membrane (Mn-CSM) was synthesized by electrospinning and Mn-CSM based packed bed reactor was constructed for catalytic ozonation, achieving excellent catalytic performance for refractory organic degradation. Mn-CSM exhibited a lamellar structure with a thickness of several hundred micrometers and was centimeter-sized in the other two dimensions, which make it easy to be separated in wastewater treatment. At the microscopic scale, Mn-CSM was composed of highly connected nanofibers, which provided large specific surface area for the exposure of active sites. In oxalic acid (OA) degradation and coal gasification wastewater advanced treatment, Mn-CSM demonstrated superior catalytic ozonation performance. After 60 min, 93% of OA was degraded in Mn-CSM based HCO process, and the effluent COD of coal gasification wastewater decreased from 105 mg L-1 to 42 mg L-1. Reactive oxygen species in aqueous solution and on catalyst surface contributed to the organic degradation. The introduction of SiO2 nanoparticles in Mn-CSM can not only enhance its catalytic stability, but also improve fluid flow field distribution. Furthermore, the presence of SiO2 increased the hydrophilicity of Mn-CSM and a better removal of hydrophilic substances (HIS) was achieved in Mn-CSM based HCO. This study highlights a Mn-CSM ozone catalyst with high catalytic activity and easy recycling capability and a Mn-CSM based catalytic ozonation process, which is promising for the degradation of refractory organics in wastewater.

关键词： Heterogeneous Catalytic Ozonation Carbon-Silica-Membrane Advanced Wastewater Treatment computational fluid dynamics simulation Hydrophobic-Hydrophilic Property

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Characterization of Supersonic Wind Tunnel Flow Quality Using Planar Laser CO₂ Rayleigh Scattering

Characterization of Supersonic Wind Tunnel Flow Quality Usin...

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AIAA Propulsion and Energy Forum / IEEE Electric Aircraft Technologies Symposium (EATS)

作者： Aguilera, Camilo Sosa, Jonathan Hyde, Evan W. Goodwin, Gabriel B. Kessler, David A. Hess, Andrew M. Miklosovic, David S. US Naval Res Lab Naval Ctr Space Technol Spacecraft Engn Div Washington DC 20375 USA US Naval Res Lab Labs Computat Phys & Fluid Dynam Washington DC 20375 USA US Naval Acad Aerosp Engn Dept Annapolis MD 21402 USA

ISBN: (数字)9781624106118

ISBN: (纸本)9781624106118

A complementary experimental and computational investigation of the flow characteristics in a supersonic wind tunnel are presented. Stereoscopic planar laser Rayleigh scattering of CO2 particles, typically several nanometers to tens of nanometers in size, were used in this study allowing cross-sectional visualization of the supersonic flow and turbulent boundary layers throughout the test section of an academic scale facility. The optical diagnostic measurements show asymmetric boundary layer growth between the top and bottom walls of the test section as well as a disturbed bottom boundary layer due to the induced pressure and velocity gradient. The computational fluid dynamics simulations were used to provide additional detail and insight into the mechanisms driving these features.

关键词： Rayleigh Scattering Hypersonic Wind Tunnels Lasers Boundary Layer Separation Compressible Flow computational fluid dynamics simulation Flow Characteristics Free Stream Velocity Reynolds Averaged Navier Stokes Static Pressure

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High-Fidelity simulations of HyMETS Arc-Jet Flows for PICA-N Modeling

High-Fidelity Simulations of HyMETS Arc-Jet Flows for PICA-N...

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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Diaz, Patricia Ventura Meurisse, Jeremie B. E. Brandis, Aaron M. Bessire, Brody K. Barnhardt, Michael Yoon, Seokkwan NASA Ames Res Ctr STC Moffett Field CA 94035 USA NASA Ames Res Ctr AMA Inc Moffett Field CA 94035 USA NASA Ames Res Ctr Moffett Field CA 94035 USA

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

Arc-jet testing is a fundamental tool in the screening of thermal protection systems under atmospheric entry conditions. In this work, high-fidelity computational fluid dynamics simulations coupled with machine learning methods for the Hypersonic Materials Environmental Test System arc-jet facility have been carried out. This effort improves the MEDLI2 data reconstruction fidelity by understanding the impact of the NuSil coating over the PICA thermocouple plugs. Thermochemical non-equilibrium models are employed to simulate the flows inside the arc-jet nozzle and chamber and machine learning techniques are used to calibrate the arc-jet inflow conditions. The material response is simulated with the recession and in-depth numerical results compared to experimental measurements.

关键词： Hypersonic Flows Thermal Protection System computational fluid dynamics simulation Thermocouples Machine Learning Jet Nozzle Stagnation Pressure Mass Flow Rate Python Pyrometer

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Research on Heat Dissipation Performance and Long-term Reliability of the Flapping Wing Cooling Technology Applied to the 5G Communications Equipment 27

Research on Heat Dissipation Performance and Long-term Relia...

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27th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC)

作者： Guo, Yanhua Zhang, Xianming Lan, Daiyan Zhu, Yue ZTE Corp Reliabil Dept Shenzhen Peoples R China

ISBN: (纸本)9781665418966

To further improve the heat dissipation efficiency of the 5G communications equipment, this study innovatively applies the flapping wing cooling technology to outdoor 5G base stations. A series of experimental and numerical studies have been conducted to explore effects of the flapping wing cooling device on heat dissipation performance and long-term reliability of 5G communications devices. Specifically, (1) Taguchi method was used to determine geometric parameters (length, width and spacing) of the flapping wing cooling device's blades, where airflow and noise were objective functions of the optimization method;(2) additionally, computational fluid dynamics simulation and thermal tests were conducted to demonstrate advantages of forced convection compared to natural convection. The results indicate that: (1) when blades of the flapping wing cooling device are 15 mm in width, 70 mm in length, 14 mm in spacing, the airflow reaches the maximum of 10.7 CFM, with the noise level meeting the permissible noise standard of the 5G outdoor devices;(2) the flapping wing cooling device reduces the temperature of electronic components of the 5G AAU by about 10 degrees C on average. The temperature drop of electronic components near the fan outlet is 6 degrees C higher than that of electronic components 0.5 m away from the fan outlet. In terms of reliability, Finite Element Method simulation was conducted to research the failure probability of the flapping wing cooling device under vibration fatigue;besides, based on a series of environmental durability tests, the reliability of the flapping wing cooling device for long-term usage outdoors was explored. The results show that: (1) the maximal Mises stress of blades is lower than fatigue limit of its own materials, and vibration fatigue life meets the requirement of 10 years;(2) the flapping wing cooling device has passed high temperature aging test, temperature cycling test, high temperature and high humidity aging test, salt sp

关键词： the flapping wing cooling device the 5G communications equipment forced convection natural convection long-term reliability computational fluid dynamics simulation Finite Element Method simulation Taguchi method

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Flow Field Features of the BeVERLI Hill Model

Flow Field Features of the BeVERLI Hill Model

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AIAA Science and Technology Forum and Exposition (AIAA SciTech Forum)

作者： Gargiulo, Aldo Duetsch-Patel, Julie E. Ozoroski, Thomas A. Beardsley, Colton T. Vishwanathan, Vidya Fritsch, Daniel J. Borgoltz, Aurelien Devenport, William J. Royz, Christopher J. Lowe, K. Todd Virginia Tech Crofton Dept Aerosp & Ocean Engn Blacksburg VA 24061 USA

ISBN: (数字)9781624106095

ISBN: (纸本)9781624106095

Wind tunnel tests and corresponding computational fluid dynamics simulations were performed to characterize surface and off-surface turbulent mean flow features of a novel superelliptic-shaped, wall-mounted, three-dimensional hill named BeVERLI (Benchmark Validation Experiment for RANS and LES Investigations). The wind tunnel tests were conducted at a hill-height-based Reynolds number of 650,000 and 0 degrees model orientation with respect to the incoming flow. Detailed measurements needed for the highest level of uncertainty quantification, study of flow sensitivites, and extensive documentation of the flow boundary conditions as per Oberkampf and Smith [1] were additionally carried out. Deviations in the as-manufactured hill model as compared to the as-designed geometry and inflow non-uniformities at the inlet of the experimental facility were identified, quantified, and used to provide additional context to the analysis of the mean flow features. Measurements on the hill identified a large leeward flow separation region and the possibility of a small laminar windward separation region. simulations predicted flow reattachment to occur at the downstream foot of the hill. Despite the symmetric nature of the BeVERLI Hill, the measurements showed asymmetric flow. Quantified asymmetries in the as-manufactured model geometry were deemed a potential cause. simulations predicted the same flow asymmetry using symmetric grids and boundary conditions, suggesting the possibility of a true asymmetric bi-modal flow behavior of the BeVERLI Hill. However, simulation parameters, such as the choice of turbulence model, were seen to affect the prediction of flow asymmetry, leaving the answer to the true nature of these asymmetries a subject of future work. The onset of deviations of the simulations from the measurements was observed at the windward transition to the hill top, where the flow experiences a strong favorable pressure gradient, suggesting the occurrence of important flow

关键词： Reynolds Averaged Navier Stokes computational fluid dynamics simulation Laminar Separation Bubble Freestream Velocity Wind Tunnel Tests Turbulence Models Particle Image Velocimetry Static Pressure Normal Stress Three Dimensional Turbulent Flow

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