Mesh relaxation effect on results quality /computation time ratio of a hybrid semi-numerical model

2016 ◽  
Author(s):  
Sofiane Ouagued ◽  
Abdourahman Aden Diriye ◽  
Yacine Amara ◽  
Georges Barakat
Keyword(s):  
Numerical Model ◽  
Computation Time ◽  
Relaxation Effect ◽  
Time Ratio

Comparison between an Advanced Numerical Simulation of Sheet Incremental Forming Using Adaptive Remeshing and Experimental Results

2013 ◽  
Vol 554-557 ◽  
pp. 1375-1381 ◽  
Author(s):  
Laurence Giraud-Moreau ◽  
Abel Cherouat ◽  
Jie Zhang ◽  
Houman Borouchaki
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Sheet Metal ◽  
Metal Forming ◽  
Tool Path ◽  
Incremental Forming ◽  
Computation Time ◽  
Experimental Results ◽  
Forming Process ◽  
Adaptive Remeshing

Recently, new sheet metal forming technique, incremental forming has been introduced. It is based on using a single spherical tool, which is moved along CNC controlled tool path. During the incremental forming process, the sheet blank is fixed in sheet holder. The tool follows a certain tool path and progressively deforms the sheet. Nowadays, numerical simulations of metal forming are widely used by industry to predict the geometry of the part, stresses and strain during the forming process. Because incremental forming is a dieless process, it is perfectly suited for prototyping and small volume production [1, 2]. On the other hand, this process is very slow and therefore it can only be used when a slow series production is required. As the sheet incremental forming process is an emerging process which has a high industrial interest, scientific efforts are required in order to optimize the process and to increase the knowledge of this process through experimental studies and the development of accurate simulation models. In this paper, a comparison between numerical simulation and experimental results is realized in order to assess the suitability of the numerical model. The experimental investigation is realized using a three-axis CNC milling machine. The forming tool consists in a cylindrical rotating punch with a hemispherical head. A subroutine has been developed to describe the tool path from CAM procedure. A numerical model has been developed to simulate the sheet incremental forming process. The finite element code Abaqus explicit has been used. The simulation of the incremental forming process stays a complex task and the computation time is often prohibitive for many reasons. During this simulation, the blank is deformed by a sequence of small increments that requires many numerical increments to be performed. Moreover, the size of the tool diameter is generally very small compared to the size of the metal sheet and thus the contact zone between the tool and the sheet is limited. As the tool deforms almost every part of the sheet, small elements are required everywhere in the sheet resulting in a very high computation time. In this paper, an adaptive remeshing method has been used to simulate the incremental forming process. This strategy, based on adaptive refinement and coarsening procedures avoids having an initially fine mesh, resulting in an enormous computing time. Experiments have been carried out using aluminum alloy sheets. The final geometrical shape and the thickness profile have been measured and compared with the numerical results. These measurements have allowed validating the proposed numerical model. References [1] M. Yamashita, M. Grotoh, S.-Y. Atsumi, Numerical simulation of incremental forming of sheet metal, J. Processing Technology, No. 199 (2008), p. 163 172. [2] C. Henrard, A.M. Hbraken, A. Szekeres, J.R. Duflou, S. He, P. Van Houtte, Comparison of FEM Simulations for the Incremental Forming Process, Advanced Materials Research, 6-8 (2005), p. 533-542.

State of the art of thermal characterization of electronic components using computational fluid dynamic tools

2017 ◽  
Vol 27 (11) ◽  
pp. 2433-2450 ◽  
Author(s):  
Eric Monier-Vinard ◽  
Brice Rogie ◽  
Valentin Bissuel ◽  
Najib Laraqi ◽  
Olivier Daniel ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Numerical Model ◽  
Effective Thermal Conductivity ◽  
Three Dimensional ◽  
Computation Time ◽  
Printed Wiring Board ◽  
Electronic Components ◽  
Content Type ◽  
Three Dimensional Representation ◽  
Wiring Board

Purpose Latest Computational Fluid Dynamics (CFDs) tools allow modeling more finely the conjugate thermo-fluidic behavior of a single electronic component mounted on a Printed Wiring Board (PWB). A realistic three-dimensional representation of a large set of electric copper traces of its composite structure is henceforth achievable. The purpose of this study is to confront the predictions of the fully detailed numerical model of an electronic board to a set of experiment results to assess their relevance. Design/methodology/approach The present study focuses on the case of a Ball Grid Array (BGA) package of 208 solder balls that connect the component electronic chip to the Printed Wiring Board. Its complete geometrical definition has to be coupled with a realistic board layers layout and a fine description of their numerous copper traces to appropriately predict the way the heat is spread throughout that multi-layer composite structure. The numerical model computations were conducted on four CFD software then compare to experiment results. The component thermal metrics for single-chip packages are based on the standard promoted by the Joint Electron Device Engineering Council (JEDEC), named JESD-51. The agreement of the numerical predictions and measurements has been done for free and forced convection. Findings The present work shows that the numerical model error is lower than 2 per cent for various convective boundary conditions. Moreover, the establishment of realistic numerical models of electronic components permits to properly apprehend multi-physics design issues, such as joule heating effect in copper traces. Moreover, the practical modeling assumptions, such as effective thermal conductivity calculation, used since decades, for characterizing the thermal performances of an electronic component were tested and appeared to be tricky. A new approach based on an effective thermal conductivity matrix is investigated to reduce computation time. The obtained numerical results highlight a good agreement with experimental data. Research limitations/implications The study highlights that the board three-dimensional modeling is mandatory to properly match the set of experiment results. The conventional approach based on a single homogenous layer using effective thermal conductivity calculation has to be banned. Practical implications The thermal design of complex electronic components is henceforth under increasing control. For instance, the impact of gold wire-bonds can now be investigated. The three-dimensional geometry of sophisticated packages, such as in BGA family, can be imported with all its internal details as well as those of its associated test board to build a realistic numerical model. The establishment of behavioral models such as DELPHI Compact Thermal Models can be performed on a consistent three-dimensional representation with the aim to minimize computation time. Originality/value The study highlights that multi-layer copper trace plane discretization could be used to strongly reduce computation time while conserving a high accuracy level.

Experimental and Numerical Investigation Into the Behavior of Buried Steel Pipelines Under Strike-Slip Fault Movement

2016 ◽  
Author(s):  
Sjors H. J. van Es ◽  
Arnold M. Gresnigt
Keyword(s):  
Numerical Model ◽  
Local Buckling ◽  
Computation Time ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Soil Conditions ◽  
Test Results ◽  
Fault Movement ◽  
Nonlinear Springs ◽  
Deformational Behavior

Buried steel pipelines for water and hydrocarbon transmission in seismic regions may be subjected to large imposed deformations. When a buried pipeline crosses an active strike-slip fault, the relative motion of the two soil bodies in which is it embedded can lead to significant deformation of the pipeline and possibly to loss of containment. To be able to fully understand the effects of this movement and the interaction between pipe and soil on the strain demands in the pipeline, a novel full scale experimental setup has been developed. To allow accurate monitoring of the pipeline deformation, the pipe-surrounding soil has been replaced with appropriate nonlinear springs, leaving the pipe bare during the experiment. In a total of ten tests, the strain demand in a pipeline as a result of these ground-induced deformations has been investigated. The testing program includes variations of pipeline geometry, steel grade and internal pressure. Furthermore, cohesive and non-cohesive soils have been simulated in the tests. Observed responses of the pipeline include local buckling, high tensile strains (up to 5%) and, in one case, cracking of the pipeline. Based on experiences with these experiments, a numerical model has been developed that uses non-linear springs to model the pipe-soil interaction. By modelling the pipe and soil conditions that were simulated in the ten experiments, this model has been calibrated and validated. Comparisons between the model predictions and test results show that the numerical model is able to predict the deformational behavior of the pipeline accurately. Moreover, also the formation of local buckles is predicted with satisfying results. The results of the validation operation lead to the conclusion that the new model is performing well. By omitting the modelling of the full soil body, computation time is reduced, increasing practical use of the developed model.

scholarly journals Numerical Modelling of Ballistic Impact Response at Low Velocity in Aramid Fabrics

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2087 ◽  
Author(s):  
Norberto Feito ◽  
José Antonio Loya ◽  
Ana Muñoz-Sánchez ◽  
Raj Das
Keyword(s):  
Numerical Model ◽  
Mechanistic Model ◽  
Computation Time ◽  
Impact Angle ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Computational Time ◽  
Low Velocity ◽  
Aramid Fabrics ◽  
The Impact

In this study, the effect of the impact angle of a projectile during low-velocity impact on Kevlar fabrics has been investigated using a simplified numerical model. The implementation of mesoscale models is complex and usually involves long computation time, in contrast to the practical industry needs to obtain accurate results rapidly. In addition, when the simulation includes more than one layer of composite ply, the computational time increases even in the case of hybrid models. With the goal of providing useful and rapid prediction tools to the industry, a simplified model has been developed in this work. The model offers an advantage in the reduced computational time compared to a full 3D model (around a 90% faster). The proposed model has been validated against equivalent experimental and numerical results reported in the literature with acceptable deviations and accuracies for design requirements. The proposed numerical model allows the study of the influence of the geometry on the impact response of the composite. Finally, after a parametric study related to the number of layers and angle of impact, using a response surface methodology, a mechanistic model and a surface diagram have been presented in order to help with the calculation of the ballistic limit.

scholarly journals NUMERICAL MODELLING OF TSUNAMI INUNUNDATION CONSIDERING THE PRESENCE OF OFFSHORE ISLANDS AND BARRIER REEFS

2018 ◽  
pp. 72
Author(s):  
Héctor Colón-De La Cruz ◽  
Peter Rivera-Casillas ◽  
Adam Keen ◽  
Patrick J. Lynett
Keyword(s):  
Numerical Model ◽  
Computation Time ◽  
University Of Southern California ◽  
Tsunami Propagation ◽  
Tsunami Waves ◽  
Near Shore ◽  
Evacuation Routes ◽  
The University ◽  
The Impact ◽  
Average User

Advances in computer programming have permitted researchers to predict and visualize how tsunami waves affect coastline areas. Although it’s possible to use numerical model simulations to predict the inundation of tsunamis, the process has some limitations. In order to solve the Boussinesq-type equations for tsunami propagation in the near-shore, it typically requires hundreds of hours of computation time and/or multiple CPUs. (Tavakkol and Lynett, 2017). Recently the University of Southern California developed a numerical model called Celeris, which can solve the Boussinesq-type equations faster than real time. The numerical model can run with minimum preparations on an average-user laptop and is able to provide results of wave inundation in a matter of seconds (Tavakkol and Lynett, 2017). The purpose of this research is to validate the results of wave inundation provided by Celeris and to study how reefs affect the inundation in the shoreline. If Celeris is validated, it could be used to study how to reduce the impact of tsunamis in the coast, explore the possibilities of using reefs to dissipate the energy of waves, improve evacuation routes, etc.

scholarly journals Development of an Elongated Ellipsoid Heat Source Model to Reduce Computation Time for Directed Energy Deposition Process

2021 ◽  
Vol 8 ◽  
Author(s):  
Vaibhav Nain ◽  
Thierry Engel ◽  
Muriel Carin ◽  
Didier Boisselier ◽  
Lucas Seguy
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Heat Source ◽  
Correction Factor ◽  
Energy Deposition ◽  
Computation Time ◽  
Metal Deposition ◽  
Time Increment ◽  
Directed Energy ◽  
Simulation Time

Directed Energy Deposition (DED) Additive Manufacturing process for metallic parts are becoming increasingly popular and widely accepted due to their potential of fabricating parts of large dimensions. The complex thermal cycles obtained due to the process physics results in accumulation of residual stress and distortion. However, to accurately model metal deposition heat transfer for large parts, numerical model leads to impractical computation time. In this work, a 3D transient finite element model with Quiet/Active element activation is developed for modeling metal deposition heat transfer analysis of DED process. To accurately model moving heat source, Goldak’s double ellipsoid model is implemented with small enough simulation time increment such that laser moves a distance of its radius over the course of each increment. Considering thin build-wall of Stainless Steel 316L fabricated with different process parameters, numerical results obtained with COMSOL 5.6 Multi-Physics software are successfully validated with experiment temperature data recorded at the substrate during the fabrication of 20 layers. To reduce the computation time, elongated ellipsoid heat input model that averages the heat source over its entire path is implemented. It has been found that by taking such large time increments, numerical model gives inaccurate results. Therefore, the track is divided into several sub-tracks, each of which is applied in one simulation increment. In this work, an investigation is done to find out the correct simulation time increment or sub-track size that leads to reduction in computation time (5–10 times) but still yields sufficiently accurate results (below 10% of relative error on temperature). Also, a Correction factor is introduced that further reduces computation error of elongated heat source. Finally, a new correlation is also established in finding out the correct time increment size and correction factor value to reduce the computation time yielding accurate results.

Modeling of Supercritical Co2 Shell-and-Tube Heat Exchangers Under Extreme Conditions. Part 2: Heat Exchanger Model

2022 ◽  
Author(s):  
Akshay Bharadwaj Krishna ◽  
Kaiyuan Jin ◽  
Portnovo Ayyaswamy ◽  
Ivan Catton ◽  
Timothy S. Fisher
Keyword(s):  
Heat Exchanger ◽  
Numerical Model ◽  
Heat Exchangers ◽  
Supercritical Co2 ◽  
Critical Role ◽  
Computation Time ◽  
Efficient Estimation ◽  
Working Fluid ◽  
Computationally Efficient ◽  
Thermal Cycles

Abstract Heat exchangers play a critical role in supercritical CO2 Brayton cycles by providing necessary waste heat recovery. Supercritical CO2 thermal cycles potentially achieve higher energy density and thermal efficiency operating at elevated temperatures and pressures. Accurate and computationally efficient estimation of heat exchanger performance metrics at these conditions is important for the design and optimization of sCO2 systems and thermal cycles. In this paper (Part II), a computationally efficient and accurate numerical model is developed to predict the performance of STHXs. Highly accurate correlations reported in Part I of this study are utilized to improve the accuracy of performance predictions, and the concept of volume averaging is used to abstract the geometry and reduce computation time. The numerical model is validated by comparison with CFD simulations and provides high accuracy and significantly lower computation time compared to existing numerical models. A preliminary optimization study is conducted and the advantage of using supercritical CO2 as a working fluid for energy systems is demonstrated.

Comment on “Study on the reliable computation time of the numerical model using the sliding temporal correlation method”

2015 ◽  
Vol 126 (3-4) ◽  
pp. 797-799
Author(s):  
Antonio Algaba ◽  
Fernando Fernández-Sánchez ◽  
Manuel Merino ◽  
Alejandro J. Rodríguez-Luis
Keyword(s):  
Numerical Model ◽  
Correlation Method ◽  
Computation Time ◽  
Temporal Correlation ◽  
Reliable Computation

scholarly journals Simulation of Nocturnal Drainage Flows Enhanced by Deep Canyons: The Rocky Flats Case

1997 ◽  
Vol 36 (6) ◽  
pp. 775-791 ◽  
Author(s):  
Melpomeni Varvayanni ◽  
John G. Bartzis ◽  
Nicolas Catsaros ◽  
Panagiotis Deligiannis ◽  
Chuck E. Elderkin
Keyword(s):  
Numerical Model ◽  
Wind Field ◽  
Atmospheric Dispersion ◽  
Ground Surface ◽  
Computation Time ◽  
Irregular Terrain ◽  
Rocky Flats ◽  
Numerical Predictions ◽  
Drainage Flows ◽  
Flow Features

Abstract The DELTA–ADREA (discretization with elements of triangle approach–atmospheric dispersion of pollutants over irregular terrain) numerical prediction model, developed at the National Center for Scientific Research Demokritos, is specifically designed to perform wind field calculations over terrains of high complexity. The numerical model has the capability to handle air–ground interaction processes by describing the ground-surface details while keeping the computation time at a reasonable level. The numerical model is applied here to a high-resolution topographical representation of the region surrounding the Rocky Flats Facility in Colorado, based on a digitized map consisting of approximately 4.8 × 106 points. Wind field calculations over the region are made using the atmospheric experimental data of 4 February 1991, collected by the participants within the Atmospheric Studies in Complex Terrain research program. The numerical predictions indicate strong drainage flows created at different altitudes with interaction between them, resulting in a quite complicated mesoscale wind field during nighttime. Available observations support the predicted flow features.

scholarly journals Development of a Condensation Model and a New Design of a Condensation Hood—Numerical and Experimental Study

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1344
Author(s):  
Mieszko Tokarski ◽  
Arkadiusz Ryfa ◽  
Piotr Buliński ◽  
Marek Rojczyk ◽  
Krzysztof Ziarko ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Numerical Model ◽  
Transport Model ◽  
Measurement Data ◽  
Computation Time ◽  
High Heat ◽  
Condensation Process ◽  
Proposed Model ◽  
Flow Heat ◽  
High Heat Load

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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