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Implementation of micropolar fluids model and hydrodynamic behavior analysis using user-defined function in FLUENT

ADVANCES IN MECHANICAL ENGINEERING 2020年第7期12卷

作者： Wang, Lian Chu, Xihua Wan, Ji Xiu, Chenxi Wuhan Univ Sch Civil Engn 8 Southern Rd East Lake Wuhan 430072 Peoples R China

Micropolar fluids commonly represent the complex fluids with microstructure, for example, animal blood and liquid crystals. To understand the behavior of micropolar fluids and the role of micropolar parameters, different micropolar fluids models were implemented by user-defined function in the FLUENT software. The correctness of user-defined function programs was verified comparing to the analytical solution in the Poiseuille flow. Then, the hydrodynamic behavior was analyzed in the Poiseuille flow with a moving particle, slider bearing, and dam break. Numerical results show that microrotation viscosity weakens translational velocity while enhances the pressure of micropolar fluids, in addition, microrotation velocity decreases with the increase in angular viscosity.

关键词： Micropolar fluids user-defined function Poiseuille flow slider bearing dam break

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Numerical simulation and optimization of ventilation and heat dissipation in main transformer room of semi-indoor substations

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APPLIED THERMAL ENGINEERING 2025年 269卷

作者： Chen, Yang Shao, Yunhao Li, Yilong Deng, Lei Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The semi-indoor substations have gained widespread application in urban areas due to the compact footprint and low maintenance costs. However, the unique structural characteristics and operational circumstances present significant challenges on the heat dissipation. This study employs the computational fluid dynamics (CFD) simulations to investigate the ventilation and heat dissipation in the main transformer room of a 110 kV semi- indoor substation. The novelty of this study lies in the integration of dynamic solar radiation modeling and air inlet optimization in the semi-indoor substations. By integrating real-time variations in solar radiation intensity employing user-defined function (UDF), this study provides a dynamic model that better reflects the transient thermal behavior of substations. The effects of air inlet angles on velocity distribution, temperature distribution, and airflow rate are evaluated. The results demonstrate that an air inlet angle of 30 degrees reduces transformer hot spot temperatures by 1 K and surface temperatures by 3 K compared to conventional 60 degrees designs, while increasing airflow rates by 18 %-22 %. Smaller angles (15 degrees-45 degrees) amplify turbulence-driven cooling but intensify temperature fluctuations, whereas larger angles (60 degrees-90 degrees) stabilize thermal distribution at the cost of 30 %-35 % airflow reduction. Dynamic solar modeling identifies peak cooling demands at 14:00, aligning heat dissipation strategies with diurnal radiation patterns. These findings establish a validated approach for optimizing passive cooling in urban substations, balancing efficiency and stability under transient conditions.

关键词： Semi-indoor substations Numerical simulation Natural ventilation user-defined function Air inlet angle Optimization design

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Numerical simulation of coupling multi-physical field in electrical arc furnace for smelting titanium slag

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Journal of Iron and Steel Research International 2023年第11期30卷 2194-2209页

作者： He-nan Cui Tao Li Chen-guang Bai Min Tan Yu-lin Zhu College of Materials Science and Engineering Chongqing UniversityChongqing400044China Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and Advanced Materials Chongqing UniversityChongqing400044China College of Metallurgy and Energy North China University of Science and TechnologyTangshan063210HebeiChina

The smelting reduction process of the ilmenite in an electric arc furnace(EAF)is a commonly used technology for producing titanium slag in the *** has particular significance to analyze the velocity-temperature-electromagnetics multi-physical field in an EAF for improving its productivity and reducing energy consumption.A transient three-dimensional mathematical model was developed to characterize the flow,heat transfer,and electromagnetic behavior in a titanium slag *** describing the electromagnetic field and its effects on velocity and temperature distribution in the furnace,magnetohydrodynamic equations and conservation equations for mass,momentum,and energy were solved simultaneously by compiling the user-defined function *** numerical model was verified by comparing with the literature *** results indicate that the Lorentz force is the main driving force of the velocity and temperature ***,the influence of input current and location of electrodes on the multi-physical field distribution was also *** is found that the appropriate range of input current and diameter of pitch circle are about 30,000 A and 3000-3500 mm,*** mathematical model established can characterize the multi-physical field more accu-rately than before,which can provide valuable guidance for the operation improvement and design optimization of the EAF for producing titanium slag.

关键词： Electric arc furnace Titanium slag Magnetohydrodynamic Multi-physical field user-defined function

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A Unified and Scalable Algorithm Framework of user-defined Temporal (k, χ)-Core Query

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 2024年第7期36卷 2831-2845页

作者： Zhong, Ming Yang, Junyong Zhu, Yuanyuan Qian, Tieyun Liu, Mengchi Yu, Jeffrey Xu Wuhan Univ Sch Comp Sci Wuhan 430072 Hubei Peoples R China South China Normal Univ Guangzhou 510631 Guangdong Peoples R China Chinese Univ Hong Kong Hong Kong Peoples R China

Querying cohesive subgraphs on temporal graphs (e.g., social network, finance network, etc.) with various conditions has attracted intensive research interests recently. In this paper, we study a novel Temporal (k,chi)-Core Query (TXCQ) that extends a fundamental Temporal k-Core Query (TCQ) proposed in our conference paper by optimizing or constraining an arbitrary metric chi of k-core, such as size, engagement, interaction frequency, time span, burstiness, periodicity, etc. Our objective is to address specific TXCQ instances with conditions on different X in a unified algorithm framework that guarantees scalability. For that, this journal paper proposes a taxonomy of measurement chi() and achieve our objective using a two-phase framework while chi() is time-insensitive or time-monotonic. Specifically, Phase 1 still leverages the query processing algorithm of TCQ to induce all distinct k-cores during a given time range, and meanwhile locates the "time zones" in which the cores emerge. Then, Phase 2 conducts fast local search and chi evaluation in each time zone with respect to the time insensitivity or monotonicity of chi(). By revealing two insightful concepts named tightest time interval and loosest time interval that bound time zones, the redundant core induction and unnecessary chi evaluation in a zone can be reduced dramatically. Our experimental results demonstrate that TXCQ can be addressed as efficiently as TCQ, which achieves the latest state-of-the-art performance, by using a general algorithm framework that leaves chi() as a user-defined function.

关键词： k-core online algorithm query processing scalability temporal graph time interval user-defined function

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Augmented lineage: traceability of data analysis including complex UDF processing

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VLDB JOURNAL 2023年第5期32卷 963-983页

作者： Yamada, Masaya Kitagawa, Hiroyuki Amagasa, Toshiyuki Matono, Akiyoshi Univ Tsukuba Grad Sch Sci & Technol 1-1-1 Tennodai Tsukuba Ibaraki Japan Univ Tsukuba Int Inst Integrat Sleep Med 1-1-1 Tennodai Tsukuba Ibaraki Japan Natl Inst Adv Ind Sci & Technol Artificial Intelligence Res Ctr Koto Ku 2-4-7 Aomi Tokyo Japan Univ Tsukuba Ctr Computat Sci 1-1-1 Tennodai Tsukuba Ibaraki Japan

Data lineage allows information to be traced to its origin in data analysis by showing how the results were derived. Although many methods have been proposed to identify the source data from which the analysis results are derived, analysis is becoming increasingly complex both with regard to the target (e.g., images, videos, and texts) and technology (e.g., AI and machine learning (ML)). In such complex data analysis, simply showing the source data may not ensure traceability. For example, ML analysts building image classifier models often need to know which parts of images are relevant to the output and why the classifier made a decision. Recent studies have intensively investigated interpretability and explainability in the AI/ML domain. Integrating these techniques into the lineage framework will help analysts understand more precisely how the analysis results were derived and how the results are trustful. In this paper, we propose the concept of augmented lineage for this purpose, which is an extended lineage, and an efficient method to derive the augmented lineage for complex data analysis. We express complex data analysis flows using relational operators by combining user-defined functions (UDFs). UDFs can represent invocations of AI/ML models within the data analysis. Then, we present a method taking UDFs into consideration to derive the augmented lineage for arbitrarily chosen tuples among the analysis results. We also experimentally demonstrate the efficiency of the proposed method.

关键词： Traceability Lineage user-defined function Complex data analysis Augmented lineage

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Modeling and analysis of effect of tool geometry on temperature distribution and material flow in friction stir welding of AA6061-T6

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JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING 2022年第4期44卷 1-24页

作者： Kumar, Manoj Kumar, Ramesh Kore, Sachin D. IIT Guwahati Dept Mech Engn Gauhati 781039 India Saharsa Coll Engn Dept Mech Engn Saharsa 852201 Bihar India IIT Goa Sch Mech Sci Ponda 403401 Goa India

A fully-coupled 3-D model of FSW was developed for 4-mm-plates of AA6061-T6 aluminum alloy based on the Finite Volume Method in ANSYS Fluent 14.5 software. Two types of the model, one with the tool and another without tool, were developed for different tool geometry, and analysis was done for temperature distribution in the workpiece and tool using system coupling for the first model and workpiece only in later one. A parametric study was carried out at different tool rotational speeds regarding temperature distribution and material flow analysis for all tool geometries at a single rotational speed. The behavior of materials was changed when passing through the different tools, and it was affected by thermal history, viscosity, and strain rate for particular tool geometry. Temperature-dependent material properties and a user-defined function viscosity code have been incorporated in the model, considering the workpiece as a non-Newtonian viscous fluid. A better material mixing was observed in the case of threaded pin geometry using a steady-state laminar flow model. All tapered tool geometries were unable to mix material properly just below and around the pin tip due to very low-velocity magnitude in this region, which may lead to a kind of defect. The asymmetric temperature distribution was observed in the workpiece. At higher rotational speed, peak temperature was observed higher in the workpiece, and the heat flow was more in the tool. Validation of the model was done by performing experiments.

关键词： user-defined function Finite volume method Friction stir welding Temperature distribution Material flow

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Experimental analysis and development of an in-house CFD condensation hood model

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HEAT AND MASS TRANSFER 2022年第2期58卷 321-336页

作者： Tokarski, Mieszko Ryfa, Arkadiusz Bulinski, Piotr Rojczyk, Marek Ziarko, Krzysztof Ostrowski, Ziemowit Nowak, Andrzej J. Silesian Tech Univ Dept Thermal Engn PL-44100 Gliwice Poland AGH Univ Sci & Technol Dept Fuels Technol Al Mickiewicza 30 PL-30059 Krakow Poland Retech Sp Zoo PL-39300 Mielec Poland

An existing condensation hood has been numerically investigated using k-epsilon turbulence and species transport models. Due to the geometrical complexity of the appliance, two additional mathematical models were introduced with the use of user defined functions (UDFs). They were a model of a fan and a model of the internally finned pipes of a heat exchanger. The latter also involved a condensation model of steam implemented by mass and energy source terms. Such an approach allowed us to avoid troublesome two-phase flow simulation and thus significantly reduced the computational effort. Based on the results provided by the numerical model, potential improvements of the heat exchanger were proposed and implemented into a second, modified numerical model. Reduction of the number of the pipes by 25% is the most important change of the developed device. Its negative effect on condensation efficiency was to be compensated by improvements of steam flow in the device. Once the modifications had been evaluated, the prototype of the device was built and tested experimentally. Both the numerical and experimental results agree and show that, the modified condensation hood is comparable to the original construction in terms of condensation efficiency, despite the significant heat transfer surface area reduction.

关键词： Condensation hood Numerical model user-defined function Heat transfer Heat exchanger

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FFR QUANTIFICATION IN A LEFT CORONARY ARTERY USING A THREE-ELEMENT WINDKESSEL MODEL AND THE NONLINEAR VISCOELASTIC PROPERTY OF BLOOD

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MATHEMATICS AND MECHANICS OF COMPLEX SYSTEMS 2023年第3期11卷 349-379页

作者： Martins, Andre A. Castro, Catarina F. Antonio, Carlos C. Sousa, Luisa C. Pinto, Sonia I. S. Univ Porto Fac Engn Porto Portugal Inst Sci & Innovat Mech & Ind Engn LAETA INEGI Porto Portugal

Atherosclerosis is a cardiovascular disease that obstructs blood flow to the heart. The fractional flow reserve (FFR) is the gold standard in assessing the func-tional significance of an intermediate coronary lesion. The goal of this study is to noninvasively calculate a patient-specific FFR value, using hemodynamic simulations under conditions as realistic as possible, and to compare it with the invasively measured FFR in the hospital. Regarding the methodology, the main novelty of this work is the use of blood's viscoelastic property in conjunction with a three-element windkessel model as a pressure boundary condition, in the hemodynamic simulations. No studies were found in the literature taking into account both assumptions *** three-element windkessel model was implemented in the present study through a user-defined function (UDF) in ANSYS software. This model has three parameters that require estimation. Three estimates were made, based either on the measured blood pressure of the patient-specific case, in the hospital, or on a higher blood pressure. Blood's viscoelastic property is considered by using the simplified Phan-Thien-Tanner (sPTT) *** invasively measured FFR is of 0.93. The noninvasive FFR, calculated by using hemodynamic simulations, is of 0.91 in all scenarios for the estimation of the model parameters. This corresponds to a relative error of 2.15% in the FFR-value *** noninvasive calculation of the FFR value appears to have low sensitivity to the model's parameter estimates. Thus, the geometry of the patient's stenosis appears to be a determining factor in the FFR value calculation.

关键词： fractional flow reserve left coronary artery windkessel model viscoelasticity user-defined function hemodynamic simulations

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Numerical investigation of heat and mass transfer characteristics within narrow channel in a packing humidifier

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DESALINATION AND WATER TREATMENT 2022年 258卷 1-15页

作者： Hua, Zhiyang Wang, Xikun Xing, Xiaolong Huang, Weiliang Gao, Zhongyang Jiangsu Univ Res Ctr Fluid Machinery Engn & Technol Zhenjiang 212013 Jiangsu Peoples R China Nanjing Univ Aeronaut & Astronaut Coll Energy & Power Engn Key Lab Thermal Management & Energy Utilizat Airc Minist Ind & Informat Technol Nanjing 210016 Jiangsu Peoples R China

A numerical investigation of air/water direct contact heat and mass transfer process, by means of the volume of fluid method in a packing humidifier, with a new two-dimensional model, is used to conduct the flow characteristic of falling film. Unlike previous models for humidifiers, penetration mass transfer theory is employed to predict the field of mass fraction of water vapor accurately. Meanwhile, the influences of water temperature, inlet air velocity, as well as the water vapor concentration in the air and structure parameters, on the heat and mass transfer process have been studied. It is found that the mass fraction of water vapor increases with the increase in the inlet water temperature and inlet air humidity, but decreases with the increase in the inlet air velocity. When the inlet air velocity increases from 0.5 to 2 m s(-1), the mass fraction of water vapor decreases from 0.029 to 0.019 kg kg(-1) (or -34.48%), resulting in the decrease in the average mass fraction of water vapor from 0.0375 to 0.026 kg kg(-1) (or -30.66%). The effects of inlet water temperature, inlet air humidity, and inlet air velocity under designed parameters are quantitatively assessed, which provide useful insight into the optimization and design of humidifier.

关键词： Heat and mass transfer user-defined function Penetration mass transfer theory Volume of fluid Humidification

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Numerical investigation of non-premixed hydrogen flame dynamics using RANS models

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Transportation Research Procedia 2025年 84卷 657-664页

作者： Hafidz Azhar Jakaria Naef A.A. Qasem Binash A. Imteyaz Department of Aerospace Engineering King Fahd University of Petroleum & Minerals (KFUPM) Dhahran 31261 Saudi Arabia Interdisciplinary Center for Aviation and Space Exploration King Fahd University of Petroleum & Minerals (KFUPM) Dhahran 31261 Saudi Arabia Interdisciplinary Research Center for Sustainable Energy Systems King Fahd University of Petroleum & Minerals (KFUPM) Dhahran 31261 Saudi Arabia

Hydrogen has sparked major stakeholders as an alternative to fossil fuel in industrial gas turbines or aerospace applications, considering its clean energy to reduce greenhouse gas emissions. Furthermore, hydrogen is known to have higher gravimetric energy density than conventional fuel. However, understanding hydrogen flames is particularly challenging due to the intricate nature of the turbulence characteristics. Hence, non-premixed turbulent hydrogen flames are numerically investigated in this work using ANSYS Fluent with and without a user-defined function. This work aims to assess the predictability of various RANS turbulence models for an axisymmetric case, including standard, modified, realizable, and Pope correction models. Simulation of test cases has shown that the realizable model exhibits the best accuracy in the centerline region further downstream with high accuracy for the centerline mean temperature. The modified model demonstrates superior predictability near the injector exit plane in the radial direction. Overall, the findings suggest that RANS models are effective for initial data collection in the early stages of the design process, providing valuable insights into the behavior of hydrogen flames.

关键词： Hydrogen flames Numerical RANS Non-premixed turbulent flame user-defined function

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