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AIAA Aviation Forum

作者： Jenkins, Michael Gopalarathnam, Ashok North Carolina State Univ Dept Mech & Aerosp Engn Raleigh NC 27695 USA

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

The production and control of aerodynamic forces is a critical aspect in motorsport-vehicle design. These vehicles frequently utilize inverted wings to generate negative lift (downforce), which results in increased lateral and longitudinal acceleration capabilities. In the case of open-wheel motorsport, these inverted wings are typically positioned at the front and rear of the vehicle in order to generate a stable aerodynamic platform, as required for both vehicle performance and safety. The work presented here focuses on the forces involved when multielement inverted airfoils are heaving in ground effect. Simulations utilizing unsteady RANS CFD have been performed on two different multielement airfoils heaving at various frequencies and mean ride heights. Contour maps of the downforce generated during a heave cycle have been plotted as functions of ride height and reduced frequency. Data relating to downforce hysteresis is presented as well. Prior work relating to single-element airfoils heaving in ground effect has shown that varying the frequency and ride height may result in a phase lag between the airfoil position and the expected height for maximum downforce. Downforce initially increases with reduction in ride height until a ride height at which it reaches a maximum. Further reduction in ride height results a reduction in the downforce due to flow separation and stall. The study presented here utilizes two multielement inverted airfoils with differing static ride-height performance. The Tyrrell 026 and the UIUC1600 airfoils have contrasting levels of downforce and stall characteristics. It has been shown that different multielement airfoils still mirror many of the force trends reported from prior work involving single element airfoils in heave. Some trends such as force hysteresis, however, are dissimilar to single element airfoil cases, as will be discussed herein.

关键词： Multielement Airfoils Freestream Mach Number Flow Separation Hysteresis Wing in Ground Effect Lift Coefficient Aircraft Wings Wind Tunnel Models Vortex Sheet simple algorithm

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Research on the simple algorithms for the Logistics Network Layout in the Mobile Network E-Commerce

Research on the Simple Algorithms for the Logistics Network ...

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International Conference on Cyber Security Intelligence and Analytics (CSIA)

作者： Ming, Fan Xian Eurasia Univ Xian 710000 Shaanxi Peoples R China

ISBN: (纸本)9783030152352;9783030152345

The e-commerce is the dominant strategy of the digital business management, which has the characteristics of guidance, innovation and sociality. Based on this, by exploring the relationship between the e-commerce and the modern logistics distribution and service activities, and combining the analysis of its status, roles, and impact, we can give full play to the advantages of the intelligent management and promote the purpose of the social and economic cycle development. In the layout activities of the e-commerce, the rational use of the simple layout algorithm is not only conducive to the improvement and development of the e-commerce system, but is also an important factor for the development of the e-commerce.

关键词： Mobile network E-commerce Logistics network layout simple algorithm

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Strategy for simulating high-speed crack propagation in 3D-plate structures based on S-version FEM

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INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES 2024年 274卷

作者： He, Tianyu Kishi, Kota Morita, Naoki Mitsume, Naoto Yanagimoto, Fuminori Kim, Yun-Jae Shibanuma, Kazuki Univ Tokyo Sch Engn 7-3-1 Bunkyo Ku Tokyo 1138656 Japan Univ Tsukuba Grad Sch Sci & Technol 1-1-1 Tennodai Tsukuba Ibaraki 3058573 Japan Nippon Kaiji Kyokai Res Inst 3-3 Kioi ChoChiyoda Ku Tokyo 1028567 Japan Korea Univ Mech Engn Seoul 02841 South Korea

Plate structures serve as the fundamental components of many large structures;therefore, dynamic crack propagation in plates is a significant safety concern. This paper proposes a novel strategy based on the s-version finite element method (s-method) for simulating high-speed crack propagation in a 3D plate structure. We employed a combination of the nodal force release technique and local mesh update method to simulate a dynamically propagating crack front. The global mesh was generated based on the entire domain geometry without considering crack propagation, which significantly simplified the mesh generation procedure, whereas the local mesh was generated only in the vicinity of the crack front with fine elements to ensure high accuracy. In the proposed strategy, the local mesh completely covered the crack front beyond the surface of the 3D plate structure. Such an incompatibility between the surface of the target domain and boundaries of the local mesh causes non-negligible errors in the conventional s-method. Hence, we propose an approach based on Heaviside enrichment to eliminate these errors. To investigate the effectiveness of the proposed strategy, numerical examples to analyse the experimental results of high-speed crack propagation in double cantilever beam-type plate specimens made of polymethyl methacrylate are presented. The numerical results demonstrated the effectiveness of the proposed strategy for simulating high-speed crack propagation in 3D plate structures. Therefore, the proposed strategy has the potential to serve as a fundamental numerical framework for simulating dynamic crack propagation in engineering structures.

关键词： s -version of finite element method fracture mechanics 3D high-speed crack propagation modelling plate structure PMMA simple algorithm

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Numerical study of oscillating lid driven cavity with the presence of an obstacle using immersed boundary method

Numerical study of oscillating lid driven cavity with the pr...

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International Conference on Recent Advances in Engineering Materials (ICRAEM)

作者： Yaswanth, Dintakurthi Maniyeri, Ranjith Natl Inst Technol Karnataka NITK Dept Mech Engn Biophys Lab Surathkal 575025 Karnataka India

In this paper, an oscillating lid driven cavity with an obstacle at center is simulated to study the effects on fluid mixing for various oscillating frequency (omega) and Reynolds number (Re). The oscillating lid promotes the generation of vortices and further presence of an obstacle breaks them into multiple sub-vortices which greatly enhance fluid mixing. This study is carried out to find the optimum parameters of the fluid mixing. It is performed by discretizing continuity and momentum equations using finite volume method on staggered grid system. The fluid-structure interaction is studied using feedback forcing scheme based immersed boundary method (IBM). A numerical model is developed and validated with previous results, and then simulations are carried out for different Re and x to find the optimum for efficient fluid mixing inside the cavity. Copyright (C) 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of 2022 International Conference on Recent Advances in Engineering Materials.

关键词： Fluid-structure interaction Immersed boundary method Lid driven cavity simple algorithm

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Experimental and Simulation Study of Harmonics in Asymmetric Multilevel Inverter Fabricated Using Four Units 6

Experimental and Simulation Study of Harmonics in Asymmetric...

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6th International Conference on Green Energy and Applications (ICGEA)

作者： Abir, Ashique Anan Kamal, Md Mostofa Prodhan, Md Imran Chakraborty, Tapan Kumar Univ Asia Pacific Dept Elect & Elect Engn Dhaka Bangladesh

ISBN: (纸本)9781665420525

This research document presents experimental and simulation studies on THD ( total harmonics distortion ) in the output voltage of a single-phase multi-level inverter built with four full-wave bridge inverters connected in cascade. Four MOSFET devices were used for each Hbridge unit. Four independent DC power supplies of different values were connected to the four Hbridge units. Proper gate drive pulses for the 16 MOSFETs of the four Hbridge units to change the switching states were generated on a microcontroller-based Arduino board. simple microcontroller programming codes was generated to simplify the complex gate control pulses of MOSFETs. It is observed that small number of power switching devices are used to obtain different levels of output voltage. The proposed system was experimentally tested in the laboratory to estimate total harmonic distortion. This experimental study also shows that the THD of the proposed inverter output voltage is decreased when voltage steps at the of the output voltages is increased. The proper switching angles in equal steps has been maintained by using proper drive pulses for power devices to reduce harmonic distortion.

关键词： equal-stepped switching angle multi-level inverter total harmonic distortion gate drive circuit simple algorithm

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Automated analysis of fatality rates for COVID 19 across different countries

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ALEXANDRIA ENGINEERING JOURNAL 2021年第1期60卷 521-526页

作者： Jabbar, Shaima Ibraheem Al Furat Al Awsat Tech Univ Babylon Tech Inst Babylon Iraq

One of the significant parameters that helps in the reporting the highest risk areas, which have COVID 19 pandemic is case fatality rate (CFR). In this work, automated analysis was carried out to evaluate fatality rate (CFR) across different countries. Furthermore, a state of art algorithm is proposed to estimate CFR and it is possible to make it applicable in the mobile phone. This application will enable us to monitor the status level of the patients (suspected, exposed and infected) to save time, efforts and get a high quailty of the recordings. All data were obtained from (https://***/coronavirus/) and pointed at the period between 27th March and 27th May 2020. Results present Spain and Egypt have a highest score of the fatality rate (approximately 24%) compared with previous research, which Italy was the highest score of the case fatality rate (CFR). On the other hand, Australia has had the lowest of the (CFR) in the current and previous researches. Furthermore, Spain has the highest percentage score of the total active cases and death rate: 0.41% and 0.00073% respectively. Documentation and comparison fatality rate of COVID 19 pandemic across different countries could assist in illustrating the strength of this pandemic, speed spreading and risk area which infected of this disease. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.

关键词： COVID 19 Case fatality rate (CFR) Health services simple algorithm Prediction

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Time-dependent economic risk analysis of the natural gas transmission pipeline system

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PROCESS SAFETY AND ENVIRONMENTAL PROTECTION 2021年 146卷 432-440页

作者： Shi, Guoyun Yu, Weichao Wang, Kun Dang, Fuhua Gong, Jing Lu, Yanan China Univ Petr Beijing Key Lab Urban Oil & Gas Distribut Technol Natl Engn Lab Pipeline Safety MOE Key Lab Petr Engn Beijing 102249 Peoples R China China Petr Planning & Engn Inst Beijing 10083 Peoples R China Oriental Huazhi Petr Engn Co Ltd Tianjin 301700 Peoples R China China Natl Petr Corp East Branch Nat Gas Mkt Co Shanghai 200120 Peoples R China

A methodology to quantify the economic risk of a natural gas transmission pipeline system is developed in this study, and the effect of the line pack is considered. The methodology is based on the risk theory and hydraulic analysis of the transmission pipeline system. In the methodology, the failure probability of the key components in the transmission pipeline system are estimated firstly. Moreover, the transient compressible model for the pipeline system is employed to perform the consequence analysis, and the model is solved by the Semi-Implicit Method for Pressure-Linked Equation (simple) algorithm in the process of the consequence analysis. By combining the failure probability estimation with the consequence analysis, the economic risk when an accident happens can be evaluated. A detailed procedure for economic risk evaluation of a natural gas transmission pipeline system is presented, and its feasibility is confirmed with a real transmission pipeline system. Furthermore, impacts of the line pack on the economic risk are investigated, and suggestions to decrease the economy risk are proposed. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： Economic risk Line pack Failure probability Gas pipeline Compressible fluid simple algorithm

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Assessments of thermal performance of hybrid and mono nanofluid U-tube solar collector system

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RENEWABLE ENERGY 2021年 171卷 1079-1096页

作者： Yildirim, Erdal Yurddas, Ali Manisa Celal Bayar Univ Dept Mech Engn TR-45140 Manisa Turkey

Solar energy systems are of great importance for water heating, where we spend most of the energy. U -tube solar collectors have a very important place in water heating among solar energy systems. Compensation of the intense energy used for water heating by this type of environmentally friendly solar energy system, will reduce CO2 and SO2 emissions for a cleaner nature. Therefore;the thermal perfor-mance of a U-tube complete system from evacuated tube solar collector (ETSC) systems was assessed. The heat transfer capability of the system, which contains 10 U-tubes, has been examined by considering the fact that it has different work fluids and different heat fluxes and flow rates. The finite volume method is used for this analysis. The model has been verified by many experimental and numerical studies. In the system under consideration has been used 10 vacuum U-tubes inclined at 30 degrees, and water and nanofluid (SiO2-Cu) which were used as working fluid in the manifolds connected to these tubes. Nanoparticles modeled in the work fluid are considered as hybrid and mono at different volume frac-tions. The thermal and hydrodynamic behaviors of the system have been examined by taking into ac-count the Boussinesq approach, and the system outlet temperatures have been calculated. As a result of analyzes and comparisons made, it has been seen that the use of nanofluid improves the thermal capability of the system under consideration. It has been determined that this improvement reaches up to 15% compared to water. The thermal effects of using SiO2 nanoparticles, which are lighter than Cu nanoparticles, were observed in terms of the precipitation problem encountered in many systems when using hybrid nanofluids. Thus, instead of using more Cu nanoparticles in volume, using smaller amounts together with SiO2 nanoparticles as a hybrid both eliminates the problem of precipitation and improves the heat capability of the work fluid. (c) 2021 Elsevier Ltd. All rights reserved.

关键词： U-tube Solar collector Hybrid Nanofluid simple algorithm Boussinesq approach

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A free element scheme for simulating two- and three-dimensional incompressible fluid flow

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS 2021年第4期93卷 1163-1182页

作者： Liu, Hua-Yu Gao, Xiao-Wei Xu, Bing-Bing Dalian Univ Technol Sch Aeronaut & Astronaut Dalian Peoples R China Dalian Univ Technol State Key Lab Struct Anal Ind Equipment Dalian Peoples R China

In this work, Free Element method (FECM) is extended to solve incompressible Navier-Stokes equations. The momentum equations are discretized by FECM, which permits overlapped elements. Then, the velocities at midpoints are interpolated by improved Momentum Interpolation Method to avoid oscillation caused by decoupling of velocity and pressure. At last, the pressure correction equation is solved to make sure the results satisfying continuity equation. The interpolation of midpoint's velocity is proved to be independent of the under-relaxation factor and time step size. The deferred correction is employed for utilization of higher-order discretization of convective terms. Taylor-Green vortex, flow over a cylinder, lid-driven flow, cooling tunnel, and flow over airfoil are simulated. The results computed by the proposed method are compared with exact solutions and benchmark solutions, which indicates that the new method has the second order accuracy in space. What is more, the proposed method works well on random node distributions as well, which means that the method is much robust.

关键词： free element method incompressible flow momentum interpolation Navier‐ Stokes equations simple algorithm

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Multi-energy flow analysis of large energy networks motivated by CFD method

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ENERGY 2024年 305卷

作者： Yang, Xiaoyu Zhou, Xiaoxin An, Ning China Elect Power Res Inst CEPRI Beijing 100192 Peoples R China

The present study focuses on multi-energy flow analysis in large energy networks. In multi-energy flow analysis, we solve different energy networks (electricity, gas, heat) in a sequence manner. The well-known simple (semiimplicit method for pressure-linked equations) algorithm is extended to solve the steady state of pipe network. Newton linearization has been used to deal with the non-linear terms in pipe network equations. Also, a p-q coupled solver is proposed. The CFD-based approaches use node methods. It is easier to deal with non-pipe elements (e.g., compressors, pumps) in pipe network analysis. Both Newton linearization based simple and p-q coupled solver are insensitive to the initial guess and can be applied in large-scale network analysis. For dynamic analysis, an implicit box scheme is used to solve the PDEs of gas network. It is stable and fitted to slow and fast boundary changing conditions, and has been applied in the co-simulation of integrated electricity-gas network. Numerical examples of gaslib-134, gaslib-135, gaslib-582, a medium-scale and two large integrated energy networks are used to validate the proposed approaches. The results show good performance compared with previous literatures.

关键词： Multi -energy flow analysis Computational fluid dynamics (CFD) simple algorithm Newton linearization p -q coupled solver Implicit box scheme

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