Journal articles on the topic 'User Defined Functions (UDF)'
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1
Zou, Jia, Amitabh Das, Pratik Barhate, Arun Iyengar, Binhang Yuan, Dimitrije Jankov, and Chris Jermaine. "Lachesis." Proceedings of the VLDB Endowment 14, no. 8 (April 2021): 1262–75. http://dx.doi.org/10.14778/3457390.3457392.
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Partitioning is effective in avoiding expensive shuffling operations. However, it remains a significant challenge to automate this process for Big Data analytics workloads that extensively use user defined functions (UDFs), where sub-computations are hard to be reused for partitionings compared to relational applications. In addition, functional dependency that is widely utilized for partitioning selection is often unavailable in the unstructured data that is ubiquitous in UDF-centric analytics. We propose the Lachesis system, which represents UDF-centric workloads as workflows of analyzable and reusable sub-computations. Lachesis further adopts a deep reinforcement learning model to infer which sub-computations should be used to partition the underlying data. This analysis is then applied to automatically optimize the storage of the data across applications to improve the performance and users' productivity.
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Song, Shuan Jun, and Dan Feng Shen. "Synthetic Flow-Field Analysis of Main and Auxiliary Nozzles in Air-Jet Looms." Advanced Materials Research 411 (November 2011): 16–20. http://dx.doi.org/10.4028/www.scientific.net/amr.411.16.
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The synthetic flow-field model of main and auxiliary nozzle flow-field in air-jet loom is introduced. The software of computational fluid dynamics FLUENT is used for the first time to simulate synthetic flow-field, and velocity vector is analyzed. To different spray angles of auxiliary nozzle, the velocity and total pressure of central air are compared in brief. The boundary conditions are changed by User Defined Functions (UDF) and the comparison analysis is done before and after using UDF.
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Gu, Yunhong, and Robert L. Grossman. "Sector and Sphere: the design and implementation of a high-performance data cloud." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1897 (June 28, 2009): 2429–45. http://dx.doi.org/10.1098/rsta.2009.0053.
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Cloud computing has demonstrated that processing very large datasets over commodity clusters can be done simply, given the right programming model and infrastructure. In this paper, we describe the design and implementation of the Sector storage cloud and the Sphere compute cloud. By contrast with the existing storage and compute clouds, Sector can manage data not only within a data centre, but also across geographically distributed data centres. Similarly, the Sphere compute cloud supports user-defined functions (UDFs) over data both within and across data centres. As a special case, MapReduce-style programming can be implemented in Sphere by using a Map UDF followed by a Reduce UDF. We describe some experimental studies comparing Sector/Sphere and Hadoop using the Terasort benchmark. In these studies, Sector is approximately twice as fast as Hadoop. Sector/Sphere is open source.
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Saur, Karla, Tara Mirmira, Konstantinos Karanasos, and Jesús Camacho-Rodríguez. "Containerized execution of UDFs." Proceedings of the VLDB Endowment 15, no. 11 (July 2022): 3158–71. http://dx.doi.org/10.14778/3551793.3551860.
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User-defined functions (UDFs) have long been used as the de facto way to extend the capabilities of data management systems. However, they are restricted to the specificities of each DBMS, and recent demands for advanced analytics have increased the need for complex UDFs that may require execution of arbitrary computation written in any programming language, management of library dependencies, portability across environments and engines, and resource isolation. These requirements go beyond what traditional UDFs were designed for, and have given rise to containerized UDFs that enable encapsulation and portability. However, this approach is nascent and can result in significant performance penalties and usability issues. In this paper, we present the first study that spans all stages of containerized UDFs' life cycle, performance bottlenecks in their execution, and extensibility to support different engines. Our experiments show that the performance of containerized UDF execution can be greatly affected by system design choices and that there are many trade-offs to consider. For example, regarding the method of communication with the containerized UDF, we show that binary-based implementations minimize overheads and are more than 2.4x faster than widely used text-based ones. Adopting a newer general-purpose communication method such as Arrow Flight can improve performance dramatically, causing a minimal ~10% slowdown compared to non-containerized UDFs. Additionally, containerized UDF start times vary wildly due to program size and complexity, from .07s to 7s in our experiments. Our insights can help DBMS developers make appropriate choices based on individual use cases when designing their systems.
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Foufoulas, Yannis, Alkis Simitsis, and Yannis Ioannidis. "YeSQL." Proceedings of the VLDB Endowment 15, no. 12 (August 2022): 3730–33. http://dx.doi.org/10.14778/3554821.3554886.
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The diversity and complexity of modern data management applications led to the extension of the relational paradigm with syntactic and semantic support for User-Defined Functions (UDFs). Although well-established in traditional DBMS settings, UDFs have become even more central in many applications spanning data science, data analytics, etc. Still, a critical limitation of UDFs, which to some extent has turned data scientists towards NoSQL systems, is the impedance mismatch between their evaluation and relational processing. We present YeSQL, an SQL extension with rich UDF support along with a pluggable architecture to easily integrate it with either server-based or embedded database engines. We currently support UDFs written in Python, which are fully integrated with relational queries as scalar functions, aggregators, or table returning functions. Key novel characteristics of YeSQL include easy implementation of complex algorithms, tracing JIT compilation of Python UDFs, and seamless integration with a database engine. Our demonstration will showcase (a) the usability and expressiveness of our approach, and (b) that our techniques of minimizing context switching between the relational engine and the Python VM are very effective and achieve significant speedups in common, practical use cases.
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Zhang, Guoqiang, Yuanchao Xu, Xipeng Shen, and Işıl Dillig. "UDF to SQL translation through compositional lazy inductive synthesis." Proceedings of the ACM on Programming Languages 5, OOPSLA (October 20, 2021): 1–26. http://dx.doi.org/10.1145/3485489.
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Many data processing systems allow SQL queries that call user-defined functions (UDFs) written in conventional programming languages. While such SQL extensions provide convenience and flexibility to users, queries involving UDFs are not as efficient as their pure SQL counterparts that invoke SQL’s highly-optimized built-in functions. Motivated by this problem, we propose a new technique for translating SQL queries with UDFs to pure SQL expressions. Unlike prior work in this space, our method is not based on syntactic rewrite rules and can handle a much more general class of UDFs. At a high-level, our method is based on counterexample-guided inductive synthesis (CEGIS) but employs a novel compositional strategy that decomposes the synthesis task into simpler sub-problems. However, because there is no universal decomposition strategy that works for all UDFs, we propose a novel lazy inductive synthesis approach that generates a sequence of decompositions that correspond to increasingly harder inductive synthesis problems. Because most realistic UDF-to-SQL translation tasks are amenable to a fine-grained decomposition strategy, our lazy inductive synthesis method scales significantly better than traditional CEGIS. We have implemented our proposed technique in a tool called CLIS for optimizing Spark SQL programs containing Scala UDFs. To evaluate CLIS, we manually study 100 randomly selected UDFs and find that 63 of them can be expressed in pure SQL. Our evaluation on these 63 UDFs shows that CLIS can automatically synthesize equivalent SQL expressions in 92% of the cases and that it can solve 2.4× more benchmarks compared to a baseline that does not use our compositional approach. We also show that CLIS yields an average speed-up of 3.5× for individual UDFs and 1.3× to 3.1× in terms of end-to-end application performance.
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Foufoulas, Yannis, Alkis Simitsis, Lefteris Stamatogiannakis, and Yannis Ioannidis. "YeSQL." Proceedings of the VLDB Endowment 15, no. 10 (June 2022): 2270–83. http://dx.doi.org/10.14778/3547305.3547328.
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The diversity and complexity of modern data management applications have led to the extension of the relational paradigm with syntactic and semantic support for User-Defined Functions (UDFs). Although well-established in traditional DBMS settings, UDFs have become central in many application contexts as well, such as data science, data analytics, and edge computing. Still, a critical limitation of UDFs is the impedance mismatch between their evaluation and relational processing. In this paper, we present YeSQL, an SQL extension with rich UDF support along with a pluggable architecture to easily integrate it with either server-based or embedded database engines. YeSQL currently supports Python UDFs fully integrated with relational queries as scalar, aggregator, or table functions. Key novel characteristics of YeSQL include easy implementation of complex algorithms and several performance enhancements, including tracing JIT compilation of Python UDFs, parallelism and fusion of UDFs, stateful UDFs, and seamless integration with a database engine. Our experimental analysis showcases the usability and expressiveness of YeSQL and demonstrates that our techniques of minimizing context switching between the relational engine and the Python VM are very effective and achieve significant speedups up to 68x in common, practical use cases compared to earlier approaches and alternative implementation choices.
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Pitchurov, George, Detelin Markov, Iskra Simova, Rositsa Velichkova, Peter Stankov, and Radostina Angelova. "Modelling indoor pollutant distribution via passive scalar and virtual box approach." E3S Web of Conferences 327 (2021): 05001. http://dx.doi.org/10.1051/e3sconf/202132705001.
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The distribution of PM2.5 around a thermal manikin with realistic female body shape in a naturally ventilated room has been modelled. The health risk (HR) due to inhalation of the PM2.5 has been quantified by integrating the pollutants mass flux over the boundaries of a virtual box around the mannequin’s head (the breathing zone). By the same approach HR is evaluated over the boundaries of another virtual box that surrounds the manikins body and defines the occupied zone. The paper focuses on the peculiarities of creating and meshing a virtual geometry, as well as on the application of user-defined functions (UDF) for defining a pollutant source within the room using Ansys Fluent modelling package.
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Kheloufi, Karim, and El Hachemi Amara. "Simulation of Geometry and Heat Transfer in a Thin Wall Produced by Direct Laser Powder Deposition." Advanced Materials Research 227 (April 2011): 134–37. http://dx.doi.org/10.4028/www.scientific.net/amr.227.134.
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A three dimensional model for direct laser powder deposition process is developed to simulate the geometry and the thermal field in building a single-bead wall (thin-wall). This model was employed using the Fluent commercial code to which several modules were appended (User Defined Functions UDF). The temperature distribution, the geometrical features of the generated structure, and thermal cycles have been carried out. We show that the results analysis can provide guidance for the process parameter selection in LPD. , and develop a base for further residual stress analysis.
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Ali, Syed Muhammad Fawad, Johannes Mey, and Maik Thiele. "Parallelizing user–defined functions in the ETL workflow using orchestration style sheets." International Journal of Applied Mathematics and Computer Science 29, no. 1 (March 1, 2019): 69–79. http://dx.doi.org/10.2478/amcs-2019-0005.
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Abstract Today’s ETL tools provide capabilities to develop custom code as user-defined functions (UDFs) to extend the expressiveness of the standard ETL operators. However, while this allows us to easily add new functionalities, it also comes with the risk that the custom code is not intended to be optimized, e.g., by parallelism, and for this reason, it performs poorly for data-intensive ETL workflows. In this paper we present a novel framework, which allows the ETL developer to choose a design pattern in order to write parallelizable code and generates a configuration for the UDFs to be executed in a distributed environment. This enables ETL developers with minimum expertise in distributed and parallel computing to develop UDFs without taking care of parallelization configurations and complexities. We perform experiments on large-scale datasets based on TPC-DS and BigBench. The results show that our approach significantly reduces the effort of ETL developers and at the same time generates efficient parallel configurations to support complex and data-intensive ETL tasks.
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Rahmati, Seyed Mohammadali, and Alireza Karimi. "A Nonlinear CFD/Multibody Incremental-Dynamic Model for A Constrained Mechanism." Applied Sciences 11, no. 3 (January 26, 2021): 1136. http://dx.doi.org/10.3390/app11031136.
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Numerical analysis of a multibody mechanism moving in the air is a complicated problem in computational fluid dynamics (CFD). Analyzing the motion of a multibody mechanism in a commercial CFD software, i.e., ANSYS Fluent®, is a challenging issue. This is because the components of a mechanism have to be constrained next to each other during the movement in the air to have a reliable numerical aerodynamics simulation. However, such constraints cannot be numerically modeled in a commercial CFD software, and needs to be separately incorporated into models through the programming environment, such as user-defined functions (UDF). This study proposes a nonlinear-incremental dynamic CFD/multibody method to simulate constrained multibody mechanisms in the air using UDF of ANSYS Fluent®. To testify the accuracy of the proposed method, Newton–Euler dynamic equations for a two-link mechanism are solved using Matlab® ordinary differential equations (ODEs), and the numerical results for the constrained mechanisms are compared. The UDF results of ANSYS Fluent® shows good agreement with Matlab®, and can be applied to constrained multibody mechanisms moving in the air. The proposed UDF of ANSYS Fluent® calculates the aerodynamic forces of a flying multibody mechanism in the air for a low simulation cost than the constraint force equation (CFE) method. The results could have implications in designing and analyzing flying robots to help human rescue teams, and nonlinear dynamic analyses of the aerodynamic forces applying on a moving object in the air, such as airplanes, birds, flies, etc.
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Han, Wei, Teng Zhang, You Liang Su, Ran Chen, Yan Qiang, and Yang Han. "Transient Characteristics of Water-Jet Propulsion with a Screw Mixed Pump during the Startup Process." Mathematical Problems in Engineering 2020 (May 4, 2020): 1–9. http://dx.doi.org/10.1155/2020/5691632.
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In order to investigate the transient hydrodynamic characteristics of water-jet propulsion with a screw mixed pump during the startup period and to overcome the difficulties in measuring the transient process parameters over a very short period of time, a method based on a flume experiment combined with computational fluid dynamics (CFD) is proposed. The thrust and torque of the pump-jet propulsion according to mooring status at different rotational speeds were measured by the test, which provided a group of data for the boundary and initial conditions of the numerical calculation of the user-defined function (UDF). Consecutive changes in the parameters of the water-jet propulsion dynamics can be captured from the numerical simulation of the startup process with the UDF. Thus, the transient hydrodynamic characteristics of water-jet propulsion according to time or rotation speed were obtained. The results show that the relationship between the thrust or torque of the water-jet propeller and pump rotational speed is close to the quadratic functions. The energy characteristic parameters of screw mixed water-jet pump, such as the flow rate, head, shaft power, and efficiency, rapidly increase and decrease and then remain relatively stable.
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Zhao, Yan-Juan, and Yu-Liang Zhang. "Transient Behavior of a Prototype Centrifugal Pump with Abrupt Decreasing Flow Rate." Shock and Vibration 2021 (April 24, 2021): 1–9. http://dx.doi.org/10.1155/2021/5586206.
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Centrifugal pump often operates at different working flow rates to meet engineering requirement. To better reveal the transient behavior of centrifugal pump in the process of decreasing flow rate, the finite volume method (FVM), RNG k-ε turbulence model, sliding mesh technology, and user-defined functions (UDF) were employed to simulate the three-dimensional unsteady viscous incompressible flow in a low-specific-speed centrifugal pump during the abrupt valve-off period. The results show that the differences are very obvious between transient and quasi-steady calculations. The velocity is maximum on the wall of hub and shroud, while the velocity is minimum and uniform distribution at middle positions. The transient flow field lags behind the quasi-steady flow field, which may be related to the reasons; namely, kinetic energy cannot convert pressure energy in time.
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Li, H. Y., H. Osman, C. W. Kang, T. Ba, and J. Lou. "Numerical and experimental studies of water disinfection in UV reactors." Water Science and Technology 80, no. 8 (October 15, 2019): 1456–65. http://dx.doi.org/10.2166/wst.2019.394.
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Abstract Performance of UV reactors for water disinfection is investigated in this paper. Both experimental and numerical studies are performed on base reactor LP24. Enterobacteria phage MS2 is chosen as the challenge microorganism in the experiments. Experiments are conducted to evaluate the effect of different parameters, i.e. flow rate and UV transmission, on the reactor performance. Simulation is carried out based on the commercial software ANSYS FLUENT with user defined functions (UDFs) implemented. The UDF is programmed to calculate UV dose absorbed by different microorganisms along their flow trajectories. The effect with boundary layer mesh and without boundary layer mesh for LP24 is studied. The results show that the inclusion of boundary layer mesh does not have much effect on the reactor performance in terms of reduction equivalent dose (RED). The numerical results agree well with the experimental measurements, hence validating the numerical model. With this achieved, the numerical model is applied to study other scaled reactors: LP12, LP40, LP60 and LP80. Comparisons show that LP40 has the highest RED and log inactivation among all the reactors while LP80 has the lowest RED and log inactivation.
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Guemmadi, M., and A. Ouibrahim. "Generalized Maxwell Model as Viscoelastic Lubricant in Journal Bearing." Key Engineering Materials 478 (April 2011): 64–69. http://dx.doi.org/10.4028/www.scientific.net/kem.478.64.
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The hydrodynamic lubrication interest is still of great importance, so that more and more elaborated lubricants are considered. They, however, involve consequently more and more hydrodynamic complexity as a result of the rheological properties of the additives. In our case, we consider lubricants having viscoelastic properties described by a generalized Maxwell model used in the case of journal bearing lubrication. The complexity of the coupled associated equations (momentum and constitutive) to describe the hydrodynamic prevailing in such a geometry requires numerical solutions. Using the commercial Finite Volume software Fluent 6.3 together with an appropriate developed computational code, via UDF (User Defined Functions), we determine the pressure distribution as well as the flow velocity profile and the stress field in the core, the load bearing capacity developed and the attitude angle; all together with the effects of the viscoelastic lubricant parameters (relaxation time and shear viscosity).
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Han, Li Ning, and Lu Min Wang. "CFD Simulation Research on Flow Characteristics of Fluidized Beds." Advanced Materials Research 881-883 (January 2014): 1809–13. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.1809.
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The Euler-Euler two-fluid model incorporating the kinetic theory of granular flow was applied to simulate the gas-solid flow in fluidized beds. The pressure drop, particle distribution and motion characteristics were studied in this paper. In order to investigate the effect of structure of the fluidized bed on flow characteristics, fluidized beds with different diameters and structures were applied. User defined functions (UDF) were applied to study the flow characteristics when the particle size and mass changed over time. The results showed that with the increase of particle size, higher minimum fluidization velocity was required, but lower pressure drop was obtained. For a certain fluidizing medium, the bed critical fluidization velocity depended only on the size and nature of the particles. The structure of a fluidized bed had an influence on the particle distribution and motion characteristics.
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Ion, Ion V., Florin Popescu, Razvan Mahu, and Eugen Rusu. "A Numerical Model of Biomass Combustion Physical and Chemical Processes." Energies 14, no. 7 (April 2, 2021): 1978. http://dx.doi.org/10.3390/en14071978.
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Identifying a modeling procedure of biomass thermal decomposition that is not only simple enough to implement and use, and computationally efficient, but also sufficiently accurate for engineering design activities, and with a spectrum of applications as broad as possible is a very difficult task. The authors propose a procedure which consists of two main stages: (a) the static modeling phase with the purpose of generating the algorithm (macro functions) that supplies a Computational Fluid Dynamics (CFD) model with specific input data (source/sink terms and local material properties) and (b) the dynamic modeling phase, where the CFD model is bi-directionally coupled to the external biomass decomposition model in the form of a User-Defined Function (UDF). The modeling approach was successfully validated against data obtained from single particle decomposition experiments, demonstrating its applicability even to large biomass particles, under high heating rates and combusting conditions.
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Trigui, Maher, Karim Gabsi, Walid Zneti, Suzelle Barrington, and Ahmed Noureddine Helal. "Finite Element Model to Predict the Bioconversion Rate of Glucose to Fructose using Escherichia coli K12 for Sugar Production from Date." International Journal of Food Engineering 11, no. 1 (February 1, 2015): 105–13. http://dx.doi.org/10.1515/ijfe-2014-0039.
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Abstract In this study, Bioconversion process of glucose to fructose from date syrup using Escherichia coli K12 is modeled using a commercial computational fluids dynamics (CFD) code fluent FLUENT 6.3.23 [8] which we implemented a user-defined functions (UDF) to simulate the interrelationships at play between various phases. A two phases CFD model was developed using an Eulerian – Eulerian approach to calculate the fructose volume fraction produced during time. The bioconversion process was studied as function of three initial concentration of glucose (0.14, 0.242 and 0.463gL–1), three induction time (60, 120 and 180 mn) and three inoculum volume (100, 120 and 150mL). The numerical results are compared with experimental data for bioconversion rate and show good agreement (R2= 0.894). The optimal condition of diffusion was obtained by applying an initial concentration of glucose less than 0.2gL–1 and induction time great than 100 minutes.
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Elgamal, Amir A., Taher Halawa, and Hesham Safwat. "Three Dimensional CFD Simulation Model with Experimental Validation of Silica Gel–Water Pair Adsorption Cooling Bed." WSEAS TRANSACTIONS ON POWER SYSTEMS 17 (December 19, 2022): 391–401. http://dx.doi.org/10.37394/232016.2022.17.39.
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In this paper, a three-dimensional full simulation model of a solar-driven adsorption cooling system integrated with user-defined functions (UDF) is successfully validated with a manufactured adsorption chamber filled with silica-gel type A. model is validated on the desorption phase with a maximum deviation error of 1.7%. Temperature with adsorption contours are shown for more understanding of the heat flow with adsorption behaviour inside the chamber in all directions. The maximum temperature at the desorption phase is reached after 300 seconds at fins area, and adsorption maximum uptake reached 0.16 kg/kg at fins wall but reached from 0.13 to 0.14 kg/kg around fins area. The average adsorption uptake reached 0.136 at the end of the adsorption process. The resultant uptake between adsorption and desorption is 0.018 kg/kg with a refrigerant mass of 1.8 kg in a complete cycle time.
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Li, Yao, Haiqing Si, Jingxuan Qiu, Yingying Shen, Peihong Zhang, and Hongyin Jia. "CFD-based structure optimization of plate bundle in plate-fin heat exchanger considering flow and heat transfer performance." International Journal of Chemical Reactor Engineering 19, no. 5 (April 12, 2021): 499–513. http://dx.doi.org/10.1515/ijcre-2020-0219.
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Abstract The plate-fin heat exchanger has been widely applied in the field of air separation and aerospace due to its high specific surface area of heat transfer. However, the low heat transfer efficiency of its plate bundles has also attracted more attention. It is of great significance to optimize the structure of plate-fin heat exchanger to improve its heat transfer efficiency. The plate bundle was studied by combining numerical simulation with experiment. Firstly, according to the heat and mass transfer theory, the plate bundle calculation model of plate-fin heat exchanger was established, and the accuracy of the UDF (User-Defined Functions) for describing the mass and heat transfer was verified. Then, the influences of fin structure parameters on the heat and mass transfer characteristics of channel were discussed, including the height, spacing, thickness and length of fins. Finally the influence of various factors on the flow field performance under different flow states was integrated to complete the optimal design of the plate bundle.
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Tošić, Marko, Roland Larsson, Janko Jovanović, Thomas Lohner, Marcus Björling, and Karsten Stahl. "A Computational Fluid Dynamics Study on Shearing Mechanisms in Thermal Elastohydrodynamic Line Contacts." Lubricants 7, no. 8 (August 12, 2019): 69. http://dx.doi.org/10.3390/lubricants7080069.
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A computational fluid dynamics (CFD) model of the thermal elastohydrodynamically lubricated (EHL) line contact problem has been developed for the purpose of exploring the physical processes that occur inside a thin EHL film subjected to shearing motion. The Navier–Stokes equations are solved by using the finite volume method (FVM) in a commercial CFD software, ANSYS Fluent. A set of user-defined functions (UDF) are used for computing viscosity, density, heat source, temperature of moving surfaces and elastic deformation of the top roller according to well-established equations commonly used in the EHL theory. The cavitation problem is solved by taking into account multiphase mixture flow. The model combinations of Houpert and Ree–Eyring and of Tait and Carreau were used for modeling the non-Newtonian behavior of Squalane and the results were compared. Both rheological models suggest the existence of shear-band and plug-flow at high fluid pressure. Due to the differences in viscosity at GPa-level pressure, the chosen model has substantial influence on the computed shear stress and temperature distributions in the high-pressure region. This shows the importance of using correct rheology information in the whole range of pressure, temperature, and shear strain rate.
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Könözsy, Laszlo, Mihaela Stefan Kharicha, Sven Eck, Meng Huai Wu, and Andreas Ludwig. "Numerical and Experimental Investigation of NH4Cl Solidification." Materials Science Forum 649 (May 2010): 367–72. http://dx.doi.org/10.4028/www.scientific.net/msf.649.367.
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This paper deals with the validation of a volume averaged multiphase solidification model based on a benchmark experiment using NH4Cl-H2O as model alloy and Particle Image Velocimetry (PIV) as optical measurement method. For the numerical modelling of the solidification, different phases (e.g. liquid, equiaxed grains and columnar dendrite trunks) have been considered. The mass, momentum, energy conservation and species transport equations for each phase have been solved. The Eulerian-Eulerian model equations have been implemented in the commercial Finite Volume Method based software FLUENT-ANSYS v6.3 using User-Defined Functions (UDF). The mass transfer has been modelled by diffusion controlled crystal growth. The simulation of the NH4Cl-H2O solidification has been numerically investigated as a two-dimensional unsteady process in the cross-section of a 100 x 80 x 10 (mm3) experimental benchmark. Since during the experiment both columnar and equiaxed growth of NH4Cl have been observed, both phenomena have been considered in the simulation. The predicted distribution of the solidification front and the measured thickness of the mushy zone have been compared with the measurements.
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Brkić, Dejan, and Zoran Stajić. "EXCEL VBA-BASED USER DEFINED FUNCTIONS FOR HIGHLY PRECISE COLEBROOK’S PIPE FLOW FRICTION APPROXIMATIONS: A COMPARATIVE OVERVIEW." Facta Universitatis, Series: Mechanical Engineering 19, no. 2 (July 11, 2021): 253. http://dx.doi.org/10.22190/fume210111044b.
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This review paper gives Excel functions for highly precise Colebrook’s pipe flow friction approximations developed by users. All shown codes are implemented as User Defined Functions – UDFs written in Visual Basic for Applications – VBA, a common programming language for MS Excel spreadsheet solver. Accuracy of the friction factor computed using nine to date the most accurate explicit approximations is compared with the sufficiently accurate solution obtained through an iterative scheme which gives satisfying results after sufficient number of iterations. The codes are given for the presented approximations, for the used iterative scheme and for the Colebrook equation expressed through the Lambert W-function (including its cognate Wright ω-function). The developed code for the principal branch of the Lambert W-function has additional and more general application for solving different problems from variety branches of engineering and physics. The approach from this review paper automates computational processes and speeds up manual tasks.
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El-Behery, Samy M., Gamal H. Badawy, and Fathi M. Mahfouz. "Three-Dimensional Simulation of Decaying Turbulent Swirling Flow Using Different Turbulence Models." International Journal of Heat and Technology 40, no. 1 (February 28, 2022): 211–18. http://dx.doi.org/10.18280/ijht.400125.
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This paper presents a numerical study of the turbulent swirling flow in a horizontal tangential inlet tube. The commercial CFD code ANSYS FLUENT 15 was used for solving the set of governing equations using different turbulence models. Eight turbulence models are tested which are, standard k–ε, realizable k–ε, RNG k–ε, SST k–ω, Non-Linear k–ε, v2-f, RSM (Quadratic Pressure-Strain Model), and RSM (Stress-Omega Model). All these turbulence models are available directly in the ANSYS FLUENT except the non-linear k–ε which was implemented in the solver using User Defined Functions (UDF). The numerical predictions are compared with experimental measurements from literature for tangential, axial velocity profiles and Reynolds stresses profiles within the tested tube. The results indicated that the axial velocity is predicted fairly well by the standard k–ε model while the tangential velocity is well predicted by RSM. On the other hand, v2-f model predicts the Reynolds stresses better than the other tested models. The statistical analysis of turbulence model performance showed that, the RSM (Quadratic Pressure-Strain) model gives the best agreement with all data of experiments followed by non-linear k–ε and standard k–ε turbulence models.
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Akhtar, Farheen, and Rajneesh Anand. "The Adsorption of Hydrogen in an Activated Carbon Tank Based on Modified Dubinin-Astakhov Model." International Journal for Research in Applied Science and Engineering Technology 11, no. 1 (January 31, 2023): 221–26. http://dx.doi.org/10.22214/ijraset.2023.48536.
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Abstract: During adsorption cycles, the simulations of thermal effects play a significant role in designing adsorption-based systems such as gas separation, gas storage and heat pumps. This paper presents the two-dimensional axisymmetric model of a hydrogen storage tank on activated carbon at a particular temperature and pressure range using User Defined Functions in Fluent (UDF). The adsorption model used for CFD analysis is based on mass, momentum and energy equations and the modified form of Dubinin-Astakhov model. The simulation is implemented through Ansys Fluent. The Linear Driving Force is applied to study the cryo-adsorption kinetics. The results are varied from pipe inlet to the tank wall based on mass flux at different flow times. The pressure and temperature profile inside the system for different inlet conditions is studied in detail. The profiles of pressure and temperature are plotted at different time intervals. The velocity distribution at various time intervals is presented for charging and discharging of hydrogen adsorption Moreover, the results are compared with the model parameters of carbon and steel by varying the thermal conductivities and specific heat capacities. The results obtained for the pressure and temperature profile shows a good agreement with the other results available in the literature.
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Tokarski, Mieszko, Arkadiusz Ryfa, Piotr Buliński, Marek Rojczyk, Krzysztof Ziarko, Ziemowit Ostrowski, and Andrzej J. Nowak. "Development of a Condensation Model and a New Design of a Condensation Hood—Numerical and Experimental Study." Energies 14, no. 5 (March 2, 2021): 1344. http://dx.doi.org/10.3390/en14051344.
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The development of a numerical model and design for the innovative construction of a heat exchanger (HE) used in a condensation hood (being a part of the combi-steamer) are described in this work. The model covers an air-steam flow, heat transfer, and a steam condensation process. The last two processes were implemented with the use of an in-house model introduced via User Defined Functions (UDF). As the condensate volume is negligible compared to the steam, the proposed model removes the condensate from the domain. This approach enabled the usage of a single-phase flow for both air and steam using a species transport model. As a consequence, a significant mesh and computation time reduction were achieved. The new heat exchanger is characterised by reorganised fluid flow and by externally finned pipes (contrary to the original construction, where internally finned pipes were used). This allowed a reduction in the number of the pipes from 48 to 5, which significantly simplifies construction and manufacturing process of the HE. The redesigned HE was tested in two cases: one simulating normal working conditions with a combi-steamer, the other with extremely high heat load. Measurement data showed that the numerical model predicted condensate mass flow rate (3.67 g/s computed and 3.56 g/s measured) and that the condensation capability increased at least by 15% when compared to the original HE design.
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Yan, Ruzhong, and Haojie Zhang. "Analysis of the dynamic characteristics of downsized aerostatic thrust bearings with different pressure equalizing grooves at high or ultra-high speed." Advances in Mechanical Engineering 13, no. 5 (May 2021): 168781402110180. http://dx.doi.org/10.1177/16878140211018078.
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This study adopts the DMT(dynamic mesh technology) and UDF(user defined functions) co-simulation method to study the dynamic characteristics of aerostatic thrust bearings with equalizing grooves and compare with the bearing without equalizing groove under high speed or ultra high speed for the first time. The effects of air film thicness, supply pressure, rotation speed, perturbation amplitude, perturbation frequency, and cross section of the groove on performance characteristics of aerostatic thrust bearing are thoroughly investigated. The results show that the dynamic stiffiness and damping coefficient of the bearing with triangular or trapezoidal groove have obvious advantages by comparing with that of the bearing without groove or with rectangular groove for the most range of air film thickness, supply pressure, rotation speed, perturbation amplitude, especially in the case of high frequency, which may be due to the superposition of secondary throttling effect and air compressible effect. While the growth range of dynamic stiffness decreases in the case of high or ultra-high rotation speed, which may be because the Bernoulli effect started to appear. The perturbation amplitude only has little influence on the dynamic characteristic when it is small, but with the increase of perturbation amplitude, the influence becomes more obvious and complex, especially for downsized aerostatic bearing.
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Könözsy, Laszlo, Anton Ishmurzin, Monika Grasser, Meng Huai Wu, Andreas Ludwig, Robert Tanzer, and Wolfgang Schützenhöfer. "Columnar to Equiaxed Transition During Ingot Casting Using Ternary Alloy Composition." Materials Science Forum 649 (May 2010): 349–54. http://dx.doi.org/10.4028/www.scientific.net/msf.649.349.
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The present paper deals with the formation of macrosegregation in a benchmark ingot using (Fe-C-Cr) ternary alloy composition. The numerical investigation of complex multiphase phenomena is a difficult study, because the thermophysical properties depend strongly on the temperature, concentration, pressure and chemical composition as well. For the numerical modeling of solidification and melting processes different phases (e.g. liquid, equiaxed crystals and columnar dendrite trunks) have been considered. The mass, momentum, energy conservation and species conservation equations for each phase have been solved. The Eulerian-Eulerian model equations have been implemented in the commercial Finite Volume Method based FLUENT-ANSYS v6.3 CFD software using User-Defined Functions (UDF). The mass transfer has been modelled by diffusion controlled crystal growth by applying an advanced tip tracking algorithm for columnar solidification. The modeling of the grain density transport has been improved. The derivatives of the mass fraction quantities for each component appear in the nucleation rate term. It means that we obtain a new term of the right hand side of the grain density transport equation for using ternary alloy composition. This paper focuses on both the process and simulation parameters and their influence on the macrosegregation formation. The results show that the macrosegregation pattern does not change significantly above a well-chosen number of grid cells, and the computational time could be decreased, when the time step size has been increased.
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Hao, Yan, Che Jun, and Chen Siyu. "One-dimensional and three-dimensional coupling simulation research of centrifugal cascade hydraulics." Kerntechnik 87, no. 2 (February 14, 2022): 176–86. http://dx.doi.org/10.1515/kern-2021-0035.
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Abstract Centrifuge cascade hydraulics research is very important for the cascade system design and safety analysis. The one-dimensional centrifugal cascade dynamic hydraulics calculation program can be used to achieve the rapid verification of the cascade system dynamic operation or accident condition. While the computational fluid dynamics (CFD) program is mainly used to analyze the local three-dimensional fluid phenomena such as the centrifugal cascade pipe and equipment. To comprehensively utilize the advantages of the two simulation methods, based on the one-dimensional calculation software SimuWorks of centrifugal cascade hydraulics and three-dimensional flow field calculation software Fluent, a one-dimensional and three-dimensional coupling simulation program for centrifugal cascade hydraulics was developed by using the API functions provided by SimuWorks simulation software and the user-defined function (UDF) of Fluent. The coupling method is used to analyze the movement of solid particles in the main feed pipe of the separation stage. By comparing the calculation results of the coupling program with the calculation results of the traditional one-dimensional dynamic hydraulics program, it can be seen that the coupling program can correctly predict the influence of feeding orifice plate clogging on the system parameters and can more intuitively show the flow field characteristics in the important parts of the system. The motion characteristics of the solid particles obtained in the simulation verification are consistent with the experimental analysis results, which further verifies the accuracy of the coupling program. The coupling program can provide a new calculation method and analytical tool for the study of centrifugal cascade hydraulics.
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Kabil, Islam, Mansour Al Qubeissi, Jihad Badra, Walid Abdelghaffar, Yehia Eldrainy, Sergei S. Sazhin, Hong G. Im, and Ahmed Elwardany. "An Improved Prediction of Pre-Combustion Processes, Using the Discrete Multicomponent Model." Sustainability 13, no. 5 (March 8, 2021): 2937. http://dx.doi.org/10.3390/su13052937.
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An improved heating and evaporation model of fuel droplets is implemented into the commercial Computational Fluid Dynamics (CFD) software CONVERGE for the simulation of sprays. The analytical solutions to the heat conduction and species diffusion equations in the liquid phase for each time step are coded via user-defined functions (UDF) into the software. The customized version of CONVERGE is validated against measurements for a single droplet of n-heptane and n-decane mixture. It is shown that the new heating and evaporation model better agrees with the experimental data than those predicted by the built-in heating and evaporation model, which does not consider the effects of temperature gradient and assumes infinitely fast species diffusion inside droplets. The simulation of a hollow-cone spray of primary reference fuel (PRF65) is performed and validated against experimental data taken from the literature. Finally, the newly implemented model is tested by running full-cycle engine simulations, representing partially premixed compression ignition (PPCI) using PRF65 as the fuel. These simulations are successfully performed for two start of injection timings, 20 and 25 crank angle (CA) before top-dead-centre (BTDC). The results show good agreement with experimental data where the effect of heating and evaporation of droplets on combustion phasing is investigated. The results highlight the importance of the accurate modelling of physical processes during droplet heating and evaporation for the prediction of the PPCI engine performance.
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Liu, Shi, Yi Yang, and Xiaobo Wu. "Simulations of Local Scour Around a Cylindrical Bridge Pier And a Semicircular Abutment Using Unsteady k-ε Model Combined with σ-Grid." Open Civil Engineering Journal 11, no. 1 (July 28, 2017): 598–614. http://dx.doi.org/10.2174/1874149501711010598.
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Introduction: Bridge scour is one of the major causes of bridge failure. Prediction of the maximum depth and shape of local scour plays an important role in bridge design and maintenance. In this paper, k-ε turbulent model combined with wall function was employed and complex flow fields are exhibited. The bed load transport model summarized by Qian and Wan [1] was applied to evaluate the development of local scour. Besides, σ-grid module was developed and embedded into the commercial solver FLUENT to fit the change of channel-bed. Method: In this module, the change of the elevation of the channel bed is calculated through using user defined functions(UDF), and the motion of the grid system is realized based on a program developed through C++ language, which extends the applications of FLUENT. The evolution of local scour hole for two cases, i.e., local scour around a cylindrical pier and a semicircular abutment, was simulated. Results and Conclusion: The depth and the shape of local scour as well as the flow fields were predicted. Numerical result conforms well to the experimental measurement. Especially, it provides fairly reasonable prediction on the key issue of the maximum scour depth. The satisfactory agreement validates the numerical method developed in the present study. In addition to the validation purpose, the different performance of this method for predicting local scour around the cylindrical pier and the semicircular abutment was discussed.
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Syahputra, Muhammad Qaidin, Denar Regata Akbi, and Diah Risqiwati. "Deteksi Dan Mitigasi Serangan DDoS Pada Software Defined Network Menggunakan Algoritma Decision Tree." Jurnal Repositor 2, no. 11 (December 4, 2020): 1491. http://dx.doi.org/10.22219/repositor.v2i11.795.
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Software Defined Network (SDN) merupakan paradigma baru dalam manajemen jaringan yang memberikan fasilitas untuk melakukan konfigurasi, virtualisasi, dan mengolah infrasturktur jaringan secara terpusat. Manajemen jaringan secara terpusat dilakukan pada SDN Controller yang dimana memisahkan network data plane dari control functions. Serangan Distributed Denial of Service (DDoS) adalah salah satu permasalahan besar dalam kemanan jaringan yang menyebabkan services yang ada pada jaringan menjadi tidak dapat diakses dalam jangka waktu tertentu. Penelitian ini bertujuan untuk membuat sistem deteksi menggunakan algortima Decision Tree dan mitigasi serangan DDoS dengan metode drop packet pada Software Defined Network. Model klasifikasi yang telah dibangun berdasarkan dataset CICIDS 2017 diterapkan pada controller dan kemudian menjadi pendeteksi serangan DDoS jenis User Data Protocol (UDP). Setiap packet in yang masuk ke dalam controller akan melalui proses pendeteksian sebelum diteruskan kepada destination source, adapun jika packet in terdeteksi sebagai serangan DDoS maka controller akan melakukan fungsi mitigasi drop packet terhadap host yang terbukti melakukan penyerangan. Dari percobaan yang telah dilakukan UDP Flood terbukti menghabiskan banyak network resources dan meningkatkan penggunaan CPU sehingga menyebabkan controller mengalami gangguan berfungsi selama proses penyerangan berlangsung. Hasil penelitian ini menunjukkan bahwa sistem yang dibuat berhasil melakukan proses deteksi dan mitigasi serangan UDP Flood dengan akurasi sebesar 99.95% dan diikuti proses mitigasi dari setiap paket yang terbukti melakukan penyerangan. Kata kunci: SDN, CICIDS 2017, UDP Flood, Decision Tree, Drop Packet.
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Joch, Lukas, and Roman Krautschneider. "VVER-440 Steam Generator’s Two-Phase Flow Analysis." Applied Mechanics and Materials 821 (January 2016): 57–62. http://dx.doi.org/10.4028/www.scientific.net/amm.821.57.
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The subject of this report is creation of three-dimensional thermal hydraulic model of horizontal steam generator for Dukovany nuclear power plant. A procedure is presented for simulation and analysis of secondary side of PGV-440 steam generator for nominal and increased reactor power. A two-fluid approach is applied for modeling physical processes inside the steam generator. Physical models were implemented in ANSYS Fluent CFD environment using User Defined Functions (UDFs). Results from this thermal hydraulic numerical model can be used for various other subsequent nuclear power plant operations and safety analysis.
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Donoso-García, Pablo, Luis Henríquez-Vargas, and Esteban Huerta. "Waste Heat Recovery from Air Using Porous Media and Conversion to Electricity." Energies 15, no. 15 (August 2, 2022): 5597. http://dx.doi.org/10.3390/en15155597.
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This paper presents a numerical study of waste heat recovery from a fluid stream using thermoelectric devices. The system consisted of a square section duct with spherical porous media placed in its central region. Hot air circulates continuously through the duct and exchanges energy with the solid matrix and subsequently with the thermoelectric modules. The mathematical model of the system was solved using ANSYS/FLUENT software, requiring the implementation of user-defined functions (UDFs) and user-defined scalars (UDS) regarding porous media and thermoelectric generation modelling. From the simulations carried out, global efficiency and electrical power values were obtained in the range of [0.11–4.51] [%] and [0.01–12.77] [W], respectively. Furthermore, for the set of variables analysed, it was observed that the performance of the system is favoured by an increase in the fluid inlet temperature and speed, as well as by a higher external heat transfer coefficient.
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Lemos, L. D., F. R. Centeno, and F. H. R. França. "EFFECTS OF TURBULENCE-RADIATION INTERACTIONS IN A NON-PREMIXED TURBULENT METHANE-AIR FLAME." Revista de Engenharia Térmica 17, no. 1 (June 30, 2018): 63. http://dx.doi.org/10.5380/reterm.v17i1.62260.
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This work studied a turbulent flame and analyzed the interaction between turbulence and radiation (TRI). The problem consists of a non-premixed turbulent methane flame surrounded by a low-velocity air coflow identified as Flame DLR-A. The steady laminar diffusion flamelet (SLDF) model is used to solve the chemical kinetics. To generate the flamelet library, turbulence-chemistry interaction is taken into account through previously assumed probability density functions (PDF) of mean scalars. Radiative heat flux is calculated with the discrete ordinates method, considering the Gray Gas model (GG). Turbulence is solved with k-ε Standard model and TRI methodology is based on temperature self-correlation. The solution is obtained using ANSYS/Fluent code coupled with user-defined functions (UDFs). Results indicated that the temperature and chemical species predictions are little affected by TRI, while the radiative quantities (radiative heat flux on the domain wall) are importantly affect by TRI effects.
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Amara, El Hachemi, Toufik Tamsaout, Karim Kheloufi, Herman Berger, and Sisa Pityana. "Numerical Study of Butt Joining by Coaxial Powder Injection." Advanced Materials Research 227 (April 2011): 17–22. http://dx.doi.org/10.4028/www.scientific.net/amr.227.17.
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A 3-D transient modelling based on the numerical resolution of the fluid flow ant the heat transfer equations is developed for butt welding using the cladding process. The physical mechanisms included in our model concern the matter melting, and the re-solidification. The implementation of developed procedures called User Defined Functions (UDFs) working interactively with Fluent CFD code, and a dynamic mesh method, allows to treat the problem with its specific and complex boundary conditions. The fusion, resolidification, and the temperature dependence of the physical properties are taken into account. As results, clad formation and information on the temperature field are obtained.
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Agati, Giuliano, Francesca Di Gruttola, Serena Gabriele, Domenico Simone, Paolo Venturini, and Domenico Borello. "Water washing of axial flow compressors: numerical study on the fate of injected droplets." E3S Web of Conferences 197 (2020): 11015. http://dx.doi.org/10.1051/e3sconf/202019711015.
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In turbomachinery applications blade fouling represents a main cause of performance degradation. Among the different techniques currently available, online water washing is one of the most effective in removing deposit from the blades. Since this kind of washing is applied when the machine is close to design conditions, injected droplets are strongly accelerated when they reach the rotor blades and the understanding of their interaction with the blades is not straightforward. Moreover, undesirable phenomena like blades erosion or liquid film formation can occur. The present study aims at assessing droplets dragging from the injection system placed at the compressor inlet till the first stage rotor blades, with a focus on droplets impact locations, on the washing process and the associated risk of erosion. 3D numerical simulations of the whole compressor geometry (up to the first rotor stage) are performed by using Ansys Fluent to account for the asymmetric distribution of the sprays around of the machine struts, IGV and rotor blades. The simulations are carried out by adopting the k-ε realizable turbulence model with standard wall functions, coupled with the discretephase model to track injected droplets motion. Droplets-wall interaction is also accounted for by adopting the Stanton-Rutland model which define a droplet impact outcome depending on the impact conditions. The induced erosion is evaluated by adopting an erosion model previously developed by some of the authors and implemented in Fluent through the use of a User Defined Function (UDF). Two sets of simulations are performed, by considering the rotor still and rotating, representative of off-line and on-line water washing conditions, respectively. In the rotating simulation, the Multiple Reference Frame Model is used. The obtained results demonstrate that the washing process differs substantially between the fixed and the rotating case. Moreover, to quantify the water washing effectiveness and the erosion risk, new indices were introduced and computed for the main components of the machine. These indices can be considered as useful prescriptions in the optimization process of water washing systems.
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Yang, Zhihui, Yicong Huang, Zuozhi Wang, Feng Gao, Yao Lu, Chen Li, and X. Sean Wang. "Demonstration of accelerating machine learning inference queries with correlative proxy models." Proceedings of the VLDB Endowment 15, no. 12 (August 2022): 3734–37. http://dx.doi.org/10.14778/3554821.3554887.
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We will demonstrate a prototype query-processing engine, which utilizes correlations among predicates to accelerate machine learning (ML) inference queries on unstructured data. Expensive operators such as feature extractors and classifiers are deployed as user-defined functions (UDFs), which are not penetrable by classic query optimization techniques such as predicate push-down. Recent optimization schemes (e.g., Probabilistic Predicates or PP) build a cheap proxy model for each predicate offline, and inject proxy models in the front of expensive ML UDFs under the independence assumption in queries. Input records that do not satisfy query predicates are filtered early by proxy models to bypass ML UDFs. But enforcing the independence assumption may result in sub-optimal plans. We use correlative proxy models to better exploit predicate correlations and accelerate ML queries. We will demonstrate our query optimizer called CORE, which builds proxy models online, allocates parameters to each model, and reorders them. We will also show end-to-end query processing with or without proxy models.
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Grulich, Philipp Marian, Steffen Zeuch, and Volker Markl. "Babelfish." Proceedings of the VLDB Endowment 15, no. 2 (October 2021): 196–210. http://dx.doi.org/10.14778/3489496.3489501.
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Today's users of data processing systems come from different domains, have different levels of expertise, and prefer different programming languages. As a result, analytical workload requirements shifted from relational to polyglot queries involving user-defined functions (UDFs). Although some data processing systems support polyglot queries, they often embed third-party language runtimes. This embedding induces a high performance overhead, as it causes additional data materialization between execution engines. In this paper, we present Babelfish, a novel data processing engine designed for polyglot queries. Babelfish introduces an intermediate representation that unifies queries from different implementation languages. This enables new, holistic optimizations across operator and language boundaries, e.g., operator fusion and workload specialization. As a result, Babelfish avoids data transfers and enables efficient utilization of hardware resources. Our evaluation shows that Babelfish outperforms state-of-the-art data processing systems by up to one order of magnitude and reaches the performance of handwritten code. With Babelfish, we bridge the performance gap between relational and multi-language UDFs and lay the foundation for the efficient execution of future polyglot workloads.
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Yang, Zhihui, Zuozhi Wang, Yicong Huang, Yao Lu, Chen Li, and X. Sean Wang. "Optimizing machine learning inference queries with correlative proxy models." Proceedings of the VLDB Endowment 15, no. 10 (June 2022): 2032–44. http://dx.doi.org/10.14778/3547305.3547310.
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We consider accelerating machine learning (ML) inference queries on unstructured datasets. Expensive operators such as feature extractors and classifiers are deployed as user-defined functions (UDFs), which are not penetrable with classic query optimization techniques such as predicate push-down. Recent optimization schemes (e.g., Probabilistic Predicates or PP) assume independence among the query predicates, build a proxy model for each predicate offline, and rewrite a new query by injecting these cheap proxy models in the front of the expensive ML UDFs. In such a manner, unlikely inputs that do not satisfy query predicates are filtered early to bypass the ML UDFs. We show that enforcing the independence assumption in this context may result in sub-optimal plans. In this paper, we propose CORE, a query optimizer that better exploits the predicate correlations and accelerates ML inference queries. Our solution builds the proxy models online for a new query and leverages a branch-and-bound search process to reduce the building costs. Results on three real-world text, image and video datasets show that CORE improves the query throughput by up to 63% compared to PP and up to 80% compared to running the queries as it is.
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Stojković, Miloš, Milan Trifunović, Jelena Milovanović, and Stojanka Arsić. "USER DEFINED GEOMETRIC FEATURE FOR THE CREATION OF THE FEMORAL NECK ENVELOPING SURFACE." Facta Universitatis, Series: Mechanical Engineering 20, no. 1 (April 8, 2022): 127. http://dx.doi.org/10.22190/fume200220034s.
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There is a growing demand for application of personalized bone implants (endoprostheses or macro-scaffolds, and fixators) which conform the anatomy of patient. Hence the need for a CAD procedure that enables fast and sufficiently accurate digital reconstruction of the traumatized bone geometry. Research presented in this paper addresses digital reconstruction of the femoral neck fracture. The results point out that User-Defined (geometric) Feature (UDF) concept is the most convenient to use in digital reconstruction of numerous variants of the same topology, such as in this kind of bone region. UDF, named FemoNeck, is developed to demonstrate capability of the chosen concept. Its geometry, controlled by a dozen of parameters, can be easily shaped according to anatomy of femoral neck region of the specific patient. That kind of CAD procedure should use minimally required set of geometric (anatomical) parameters, which can be easily captured from X-ray or Computed Tomography (CT) images. For the statistical analysis of geometry and UDF development we used CT scans of proximal femur of 24 Caucasian female and male adults. The validation of the proposed method was done by applying it for remodeling four femoral necks of four different proximal femurs and by comparing the geometrical congruency between the raw polygonal models gained directly from CT scan and reconstructed models.
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Swar, Rohan, Awatef Hamed, Dongyun Shin, Nathanial Woggon, and Robert Miller. "Deterioration of Thermal Barrier Coated Turbine Blades by Erosion." International Journal of Rotating Machinery 2012 (2012): 1–10. http://dx.doi.org/10.1155/2012/601837.
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A combined experimental and computational study was conducted to investigate the erosion of thermal barrier coated (TBC) blade surfaces by alumina particles ingestion in a single-stage turbine. In the experimental investigation, tests were performed to determine the erosion rates and particle restitution characteristics under different impact conditions. The experimental results show that the erosion rates increase with increased impingement angle, impact velocity, and temperature. In the computational simulations, an Euler-Lagrangian two-stage approach is used in obtaining numerical solutions to the three-dimensional compressible Reynolds-Averaged Navier-Stokes equations and the particles equations of motion in each blade passage reference frame. User defined functions (UDFs) were developed to represent experimentally based correlations for particle surface interaction models and TBC erosion rates models. UDFs were employed in the three-dimensional particle trajectory simulations to determine the particle rebound characteristics and TBC erosion rates on the blade surfaces. Computational results are presented in a commercial turbine and a NASA-designed automotive turbine. The similarities between the erosion patterns in the two turbines are discussed for uniform particle ingestion and for particle ingestion concentrated in the inner and outer 5% of the stator blade span to represent the flow cooling of the combustor liner.
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Siddiqui, Tarique, Surajit Chaudhuri, and Vivek Narasayya. "COMPARE." Proceedings of the VLDB Endowment 14, no. 11 (July 2021): 2419–31. http://dx.doi.org/10.14778/3476249.3476291.
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Data analysis often involves comparing subsets of data across many dimensions for finding unusual trends and patterns. While the comparison between subsets of data can be expressed using SQL, they tend to be complex to write, and suffer from poor performance over large and high-dimensional datasets. In this paper, we propose a new logical operator COMPARE for relational databases that concisely captures the enumeration and comparison between subsets of data and greatly simplifies the expressing of a large class of comparative queries. We extend the database engine with optimization techniques that exploit the semantics of COMPARE to significantly improve the performance of such queries. We have implemented these extensions inside Microsoft SQL Server, a commercial DBMS engine. Our extensive evaluation on synthetic and real-world datasets shows that COMPARE results in a significant speedup over existing approaches, including physical plans generated by today's database systems, user-defined functions (UDFs), as well as middleware solutions that compare subsets outside the databases.
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Saha, Rajib Kumar, Madhumita Ray, and Chao Zhang. "Computational fluid dynamics simulation and parametric study of an open channel ultra-violet wastewater disinfection reactor." Water Quality Research Journal 50, no. 1 (October 17, 2014): 58–71. http://dx.doi.org/10.2166/wqrjc.2014.034.
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The disinfection characteristics of an open channel ultra-violet (UV) disinfection reactor is investigated numerically. The computational fluid dynamics (CFD) model used in this study is based on the volume of fluid (VOF) method to capture the water–air interface. The Lagrangian particle tracking method is used to calculate the microbial particle trajectory and the discrete ordinate (DO) model is used to calculate the UV intensity field inside the reactor. A commercial CFD software package ANSYS FLUENT is used to solve the governing equations. Custom user defined functions (UDFs) are developed to calculate the UV doses. A post-processor is developed in MATLAB to implement the inactivation kinetics of the microbes. The post-processor provides the probabilistic dose distribution and reduction equivalent dose (RED) values achievable in the reactor. The numerical predictions are compared with available experimental data to validate the CFD model. A parametric study is performed to understand the effects of different parameters on disinfection performance of the reactor. The low/high dosed particle trajectories, which can provide an insight for hydraulic and optical characteristics of the reactor for possible design improvements, are identified.
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Zhao, Bin, Shuangmei Zhou, Jianmei Feng, Xueyuan Peng, and Xiaohan Jia. "Application of a Fluid–Structure Interaction Model for Analysis of the Thermodynamic Process and Performance of Boil-Off Gas Compressors." Entropy 21, no. 4 (March 28, 2019): 341. http://dx.doi.org/10.3390/e21040341.
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Boil-off gas (BOG) compressors are among the most critical devices in transportation and receiving systems for liquid natural gas (LNG) because they are used to pump out excess BOG from LNG storage tanks to ensure safety. Because of the ultralow suction temperature, the influence of heat transfer between the cold gas and the compressor parts on the in-cylinder thermodynamic process cannot be ignored. This paper reports the effects of suction temperature on the thermodynamic process and performance of a BOG compressor with consideration of gas pulsation. A computational fluid dynamics (CFD) model with dynamic and sliding meshes was established, in which user-defined functions (UDFs) were used to calculate the real-time valve lift to realize coupling between the thermodynamic process and the gas pulsation, and a performance test rig was constructed to verify the proposed numerical model. The simulated results agreed well with the experimental ones. The results show that as the suction temperature decreased from 30 °C to −150 °C, the first-stage volumetric efficiency decreased to 0.69, and the preheating increased to 45.8 °C. These results should provide academic guidance and an experimental basis for the design and optimization of BOG compressors.
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Zhuo, Youwei, Jingji Chen, Gengyu Rao, Qinyi Luo, Yanzhi Wang, Hailong Yang, Depei Qian, and Xuehai Qian. "Distributed Graph Processing System and Processing-in-memory Architecture with Precise Loop-carried Dependency Guarantee." ACM Transactions on Computer Systems 37, no. 1-4 (June 2021): 1–37. http://dx.doi.org/10.1145/3453681.
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To hide the complexity of the underlying system, graph processing frameworks ask programmers to specify graph computations in user-defined functions (UDFs) of graph-oriented programming model. Due to the nature of distributed execution, current frameworks cannot precisely enforce the semantics of UDFs, leading to unnecessary computation and communication. It exemplifies a gap between programming model and runtime execution. This article proposes novel graph processing frameworks for distributed system and Processing-in-memory (PIM) architecture that precisely enforces loop-carried dependency; i.e., when a condition is satisfied by a neighbor, all following neighbors can be skipped. Our approach instruments the UDFs to express the loop-carried dependency, then the distributed execution framework enforces the precise semantics by performing dependency propagation dynamically. Enforcing loop-carried dependency requires the sequential processing of the neighbors of each vertex distributed in different nodes. We propose to circulant scheduling in the framework to allow different nodes to process disjoint sets of edges/vertices in parallel while satisfying the sequential requirement. The technique achieves an excellent trade-off between precise semantics and parallelism—the benefits of eliminating unnecessary computation and communication offset the reduced parallelism. We implement a new distributed graph processing framework SympleGraph, and two variants of runtime systems— GraphS and GraphSR —for PIM-based graph processing architecture, which significantly outperform the state-of-the-art.
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Xekalaki, Maria, Juan Fumero, Athanasios Stratikopoulos, Katerina Doka, Christos Katsakioris, Constantinos Bitsakos, Nectarios Koziris, and Christos Kotselidis. "Enabling Transparent Acceleration of Big Data Frameworks Using Heterogeneous Hardware." Proceedings of the VLDB Endowment 15, no. 13 (September 2022): 3869–82. http://dx.doi.org/10.14778/3565838.3565842.
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The ever-increasing demand for high performance Big Data analytics and data processing, has paved the way for heterogeneous hardware accelerators, such as Graphics Processing Units (GPUs) and Field Programmable Gate Arrays (FPGAs), to be integrated into modern Big Data platforms. Currently, this integration comes at the cost of programmability since the end-user Application Programming Interface (APIs) must be altered to access the underlying heterogeneous hardware. For example, current Big Data frameworks, such as Apache Spark, provide a new API that combines the existing Spark programming model with GPUs. For other Big Data frameworks, such as Flink, the integration of GPUs and FPGAs is achieved via external API calls that bypass their execution models completely. In this paper, we rethink current Big Data frameworks from a systems and programming language perspective, and introduce a novel co-designed approach for integrating hardware acceleration into their execution models. The novelty of our approach is attributed to two key design decisions: a) support for arbitrary User Defined Functions (UDFs), and b) no modifications to the user level API. The proposed approach has been prototyped in the context of Apache Flink, and enables unmodified applications written in Java to run on heterogeneous hardware, such as GPU and FPGAs, transparently to the users. The performance evaluation of the proposed solution has shown performance speedups of up to 65x on GPUs and 184x on FPGAs for suitable workloads of standard benchmarks and industrial use cases against vanilla Flink running on traditional multi-core CPUs.
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Liu, Chenghong, Xueyong Ding, Hegong Liu, Xinlin Yan, Chao Dong, and Jia Wang. "Numerical Analysis on Characteristics of Reduction Process within a Pre-Reduction Rotary Kiln." Metals 11, no. 8 (July 25, 2021): 1180. http://dx.doi.org/10.3390/met11081180.
Full textAbstract:
The reduction process inside the ore pre-reduction rotary kiln involves a series of physicochemical reactions, and in-depth understanding of the reduction behavior is helpful to improve the product quality and productivity. This paper reports a three-dimensional steady state mathematical model based on computational fluid dynamics, which considers heat transfer, mass transfer and chemical reactions inside the rotary kiln. A user-defined functions (UDFs) program in C language is developed to define physical parameters and chemical reactions, and calculate the heat and mass transfer between freeboard and bed regions. The model is validated by measurement data and is then used to investigate the detailed information inside the rotary kiln. The results show that there is a temperature gradient in the bed, which is maximal near the kiln tail and decreases gradually as the reduction process progresses. The result also confirms that the reduction of FeO to Fe is the limiting step of the whole reduction process because this reaction requires a higher reduction potential. Furthermore, the influence of C/O mole ratio and fill degree are analyzed by comparing the average bed temperature, reduction potential and metallization ratio.
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Mu, Lin, and Hong Chao Yin. "Numerical Simulation of the Influence of Deposits on Heat Transfer Process in a Heat Recovery Steam Generator." Applied Mechanics and Materials 121-126 (October 2011): 1301–5. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.1301.
Full textAbstract:
Flue gas entrains a large number of ash particles which are composed of alkali substances into the heat recovery steam generator (HRSG). The deposition of particles on the tube surface of heat transfer can reduce the heat transfer efficiency significantly. In the present work, an Eulerian- Lagrangian model based on Computational Fluid Dynamics (CFD) is implemented to simulation flue gas turbulent flow, heat transfer and the particle transport in the HRSG. Several User-Defined Functions (UDFs) are developed to predict the particle deposition/ rebounding as well as the influence of physical properties and microstructure of deposits on the heat transfer process. The results show that only after one day deposition, the total heat transfer rate reduces 27.68% compared with the case no deposition. Furthermore, the total heat transfer rate reduces to only 238.74kW after 30 days of continuous operation without any slag removal manipulation. Both numerical simulation and field measurement identify that the deposits play an important role in the heat transfer in the HRSG. Especially, when the deposits can’t be removed designedly according to the actual operating conditions, the HRSG experiences a noticeable decline in heat transfer efficiency due to continuous fouling and slagging on the tube surface.
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Huang, Bao Hua, Tian Jing Wang, Yan Ma, and Feng Jiang. "Schema of Enhancing User Authentication and Encrypting Lob Data in ODBC Driver for Database." Applied Mechanics and Materials 543-547 (March 2014): 3688–91. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.3688.
Full textAbstract:
For commercial database management system is not suitable for storing sensitive data, the data is often encrypted in application before keeping into database. Using UDF (User Defined Function) can simplify the encrypting procedure, but it can't handle Lob (Long object) data. A schema of enhancing user authentication and encrypting Lob data in ODBC (Open Database Connection) driver for database is prosed. By adding necessary attributes of user authentication and cipher algorithm to encrypt Lob data in ODBC driver, the security of data stored in database is improved. Experiments show that the schema is transparent, efficient, easy to implement and reliable.