Thematische Bibliographien / Reduced Length Modeling

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Auswahl der wissenschaftlichen Literatur zum Thema „Reduced Length Modeling“

Autor: Grafiati

Veröffentlicht am 25. Juni 2021

Zuletzt aktualisiert am 10. Februar 2022

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Zeitschriftenartikel zum Thema "Reduced Length Modeling"

Kwon, O., und F. E. Ames. „A Velocity and Length Scale Approach to k–ε Modeling“. Journal of Heat Transfer 118, Nr. 4 (01.11.1996): 857–63. http://dx.doi.org/10.1115/1.2822581.

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This paper describes a velocity and length scale approach to low-Reynolds-number k–ε modeling, which formulates the eddy viscosity on the normal component of turbulence and a length scale. The normal component of turbulence is modeled based on the dissipation and distance from the wall and is bounded by the isotropic condition. The model accounts for the anisotropy of the dissipation and the reduced length of mixing in the near wall region. The kinetic energy and dissipation rate were computed from the k and ε transport equations of Durbin (1993). The model was tested for a wide range of turbulent flows and proved to be superior to other k–ε based models.

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Liu, Yujiong, und Pinhas Ben-Tzvi. „Dynamic Modeling, Analysis, and Design Synthesis of a Reduced Complexity Quadruped with a Serpentine Robotic Tail“. Integrative and Comparative Biology 61, Nr. 2 (17.05.2021): 464–77. http://dx.doi.org/10.1093/icb/icab083.

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Synopsis Serpentine tail structures are widely observed in the animal kingdom and are thought to help animals to handle various motion tasks. Developing serpentine robotic tails and using them on legged robots has been an attractive idea for robotics. This article presents the theoretical analysis for such a robotic system that consists of a reduced complexity quadruped and a serpentine robotic tail. Dynamic model and motion controller are formulated first. Simulations are then conducted to analyze the tail’s performance on the airborne righting and maneuvering tasks of the quadruped. Using the established simulation environment, systematic analyses on critical design parameters, namely, the tail mounting point, tail length, torso center of mass (COM) location, tail–torso mass ratio, and the power consumption distribution, are performed. The results show that the tail length and the mass ratio influence the maneuvering angle the most while the COM location affects the landing stability the most. Based on these design guidelines, for the current robot design, the optimal tail parameters are determined as a length of two times as long as the torso length and a weight of 0.09 times as heavy as the torso weight.

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Chowdhury, Md Arman, Ahmad Rahmzadeh, Saber Moradi und M. Shahria Alam. „Feasibility of using reduced length superelastic shape memory alloy strands in post-tensioned steel beam–column connections“. Journal of Intelligent Material Systems and Structures 30, Nr. 2 (12.11.2018): 283–307. http://dx.doi.org/10.1177/1045389x18806393.

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Driven by a need to reduce repair costs and downtime in structures following a major earthquake, self-centering systems have been introduced. Post-tensioned high strength steel strands have shown promising results in providing self-centering capability in steel frames, where the beams are compressed to columns. This study aims at investigating the feasibility of using reduced length of steel and shape memory alloy strands in steel beam–column connections. Through finite element modeling, the study first evaluates the effect of using short-length regular post-tensioned strands in steel connections. The results show higher strength, stiffness, and energy dissipation capacity for connections with shorter length regular post-tensioned strands. The moment capacity and energy absorption capacity of a post-tensioned beam–column connection with one-third strand length were 105% and 114% higher than those of with full-length strands, respectively. However, residual drifts increased from 4 to 39 mm. To avoid loss in the re-centering capability of such connections due to yielding/failing of post-tensioned steel strands, the application of shape memory alloy and hybrid strands are proposed. The results show that shorter length shape memory alloy strands are effective in regaining self-centering and dissipating higher amount of energy compared to the full-length steel strands.

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Xu, Shi Xian, Yu Zhang, Meng Lan Duan und Bing Dai. „Three-Dimensional Modeling of Single-Lap Joints with Variable Interfacial Crack Length “. Key Engineering Materials 665 (September 2015): 161–64. http://dx.doi.org/10.4028/www.scientific.net/kem.665.161.

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This paper investigated the performance of single-lap joints with interfacial crack through the finite element method. The finite element method was validated by the G-R solutions at first. And then the influence of geometric parameter of the joint as well as the length of the interfacial crack were discussed. Results showed that the presence of a spew fillet can reduced the stress intensity factors (SIF).The relationship of the crack length ratio and SIF, adhesive thickness ratio and SIF were built.

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Yilmaz, Ibrahim, Ece Ayli und Selin Aradag. „Investigation of the Effects of Length to Depth Ratio on Open Supersonic Cavities Using CFD and Proper Orthogonal Decomposition“. Scientific World Journal 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/810175.

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Simulations of supersonic turbulent flow over an open rectangular cavity are performed to observe the effects of length to depth ratio (L/D) of the cavity on the flow structure. Two-dimensional compressible time-dependent Reynolds-averaged Navier-Stokes equations with k-ωturbulence model are solved. A reduced order modeling approach, Proper Orthogonal Decomposition (POD) method, is used to further analyze the flow. Results are obtained for cavities with severalL/Dratios at a Mach number of 1.5. Mostly, sound pressure levels (SPL) are used for comparison. After a reduced order modeling approach, the number of modes necessary to represent the systems is observed for each case. The necessary minimum number of modes to define the system increases as the flow becomes more complex with the increase in theL/Dratio. This study provides a basis for the control of flow over supersonic open cavities by providing a reduced order model for flow control, and it also gives an insight to cavity flow physics by comparing several simulation results with different length to depth ratios.

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Anderson, L. S., und R. S. Anderson. „Modeling debris-covered glaciers: extension due to steady debris input“. Cryosphere Discussions 9, Nr. 6 (23.11.2015): 6423–70. http://dx.doi.org/10.5194/tcd-9-6423-2015.

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Abstract. Debris-covered glaciers are common in rapidly-eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. If continuous debris cover is present, mass balance gradients can be reduced leading to increases in glacier length. In order to quantify feedbacks in the debris-glacier-climate system, we developed a 2-D long-valley numerical glacier model that includes englacial and supraglacial advection. We ran 120 simulations in which a steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier. Our model and parameter selections produce two-fold increases in glacier length. Debris flux onto the glacier and the relationship between debris thickness and melt rate strongly control glacier length. Debris deposited near the equilibrium-line altitude, where ice discharge is high, results in the greatest glacier extension when other debris related variables are held constant. Continuous debris cover reduces ice discharge gradients, ice thickness gradients, and velocity gradients relative to initial debris-free glaciers. Debris-forced glacier extension decreases the ratio of accumulation zone to total glacier area (AAR). The model reproduces first-order relationships between debris cover, AARs, and glacier surface velocities from glaciers in High Asia. We provide a quantitative, theoretical foundation to interpret the effect of debris cover on the moraine record, and to assess the effects of climate change on debris-covered glaciers.

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Anderson, Leif S., und Robert S. Anderson. „Modeling debris-covered glaciers: response to steady debris deposition“. Cryosphere 10, Nr. 3 (26.05.2016): 1105–24. http://dx.doi.org/10.5194/tc-10-1105-2016.

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Abstract. Debris-covered glaciers are common in rapidly eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. If continuous debris cover is present, ablation rates can be significantly reduced leading to increases in glacier length. In order to quantify feedbacks in the debris–glacier–climate system, we developed a 2-D long-valley numerical glacier model that includes englacial and supraglacial debris advection. We ran 120 simulations on a linear bed profile in which a hypothetical steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier terminus. Our model and parameter selections can produce 2-fold increases in glacier length. Debris flux onto the glacier and the relationship between debris thickness and melt rate strongly control glacier length. Debris deposited near the equilibrium-line altitude, where ice discharge is high, results in the greatest glacier extension when other debris-related variables are held constant. Debris deposited near the equilibrium-line altitude re-emerges high in the ablation zone and therefore impacts melt rate over a greater fraction of the glacier surface. Continuous debris cover reduces ice discharge gradients, ice thickness gradients, and velocity gradients relative to initial debris-free glaciers. Debris-forced glacier extension decreases the ratio of accumulation zone to total glacier area (AAR). Our simulations reproduce the "general trends" between debris cover, AARs, and glacier surface velocity patterns from modern debris-covered glaciers. We provide a quantitative, theoretical foundation to interpret the effect of debris cover on the moraine record, and to assess the effects of climate change on debris-covered glaciers.

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Mehr, E. H., und H. R. Saba. „Ductility Evaluation of Steel Structures with Reduced Beam Sections and Post-Tensioned Cables Using the Finite Element Method“. Engineering, Technology & Applied Science Research 7, Nr. 6 (18.12.2017): 2236–39. http://dx.doi.org/10.48084/etasr.1568.

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Given the importance of structure strengthening, this research introduces a particular type of steel structure in which the reduced beam section and post-tensioned cables were used for creating centralized property and preventing the formation of plastic hinges in the beam and columns. After introducing the system, ABAQUS modeling results are compared with a reliable laboratory sample to check its accuracy. Good convergence was seen which shows the modeling accuracy. The results of the model’s nonlinear static analysis revealed that the above steel structure has higher ductility when compared to conventional steel structures. Also, the results showed that with the rising of height, span length and early post-tensioned power of the cables we can increase the ductility of the structure.

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Cheng, Fang-Yi, Chin-Fang Lin, Yu-Tzu Wang, Jeng-Lin Tsai, Ben-Jei Tsuang und Ching-Ho Lin. „Impact of Effective Roughness Length on Mesoscale Meteorological Simulations over Heterogeneous Land Surfaces in Taiwan“. Atmosphere 10, Nr. 12 (12.12.2019): 805. http://dx.doi.org/10.3390/atmos10120805.

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The Weather Research and Forecasting (WRF) modeling system obtains the aerodynamic roughness length (z0) from a land use (LU) lookup table. The effective aerodynamic roughness length (z0eff) was estimated for the island of Taiwan by considering the individual roughness lengths (z0i) of the underlying LU types within a modeling grid box. Two z0eff datasets were prepared: one using the z0i from the default LU lookup table and the other using the observed z0i for three LU types (urban, dry cropland and pasture, and irrigated cropland and pasture). The spatial variability of the z0eff distribution was higher than that of the LU table-based z0 distribution. Three WRF sensitivity experiments were performed: (1) dominant LU table-based z0 (namely, S1), (2) z0eff estimated from the default z0i (namely, S2), and (3) z0eff estimated from the observed z0i (namely, S3). Comparisons of the thermal field, temperature, and surface sensible and latent heat fluxes revealed no significant differences among the three simulations. The wind field overestimation and surface momentum flux underestimation in S1 were reduced in S2 and S3, and these improvements were more prominent over areas with highly heterogeneous land surface conditions.

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Zhou, Beibei, Xiaopeng Chen, Lijun Su, Hujun Li, Quanjiu Wang und Wanghai Tao. „Evaluation and modeling of factors influencing the depth of mixing layer in which soil solute releasing from soil to surface runoff“. Canadian Journal of Soil Science 101, Nr. 3 (01.09.2021): 415–29. http://dx.doi.org/10.1139/cjss-2020-0141.

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The depth of mixing layer is one of the important parameters which cannot be assigned a constant value affected by many factors in the slope runoff. The objective of this study was to investigate the effect of slope length and underground biomass on slope runoff, solute transport processes, as well as mixing layer depth. In this study, the experimental plots with the four slope lengths (5, 10, 15, and 20 m) and a width of 2 m were built on the slope with the gradient of 20°. In addition, the plots with the millet or wheat planting were built on the slope. The change of runoff and solute transport was analyzed through simulated rainfall experiments and then to estimate mixing layer depth. The results showed that the runoff rate decreased and more runoff seeped into the slope soil with increasing slope length. Increasing underground biomass also promoted greater rainfall infiltration into the soil. The increase in slope length increased the concentration of solute in runoff, but more underground biomass reduced the nutrients transported with runoff. The effective mixing depth increased with an increase in slope length, but effective mixing depth decreased with increased underground biomass. The modified expression of the equivalent mixing model under different slope lengths and underground biomass could accurately describe the solute transfer process in runoff when compared with complete mixing model and incomplete mixing model based on exponential functions. This research provided a reference for improving the application of mixing layer models in the slope management.

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Dissertationen zum Thema "Reduced Length Modeling"

Losey, Bradley. „Analysis of Magnetic Gear End-Effects to Increase Torque and Reduce Computation Time“. The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595514209192582.

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Kemp, SCOTT CONNOR. „Evaluating the Accuracy of Finite Element Models at Reduced Length Scales“. Thesis, 2013. http://hdl.handle.net/1974/8363.

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Finite element models are used frequently in both engineering and scientific research. While they can provide useful information as to the performance of materials, as length scales are decreased more sophisticated model descriptions are required. It is also important to develop methods by which existing models may be verified against experimental findings. The present study evaluates the ability of various finite element models to predict materials behaviour at length scales ranging from several microns to tens of nanometers. Considering this motivation, this thesis is provided in manuscript form with the bulk of material coming from two case studies. Following an overview of relevant literature in Chapter 2, Chapter 3 considers the nucleation of delta-zirconium hydrides in a Zircaloy-2 matrix. Zirconium hydrides are an important topic in the nuclear industry as they form a brittle phase which leads to delayed hydride cracking during reactor start-up and shut-down. Several FE models are used to compare present results with literature findings and illustrate the weaknesses of standard FE approaches. It is shown that standard continuum techniques do not sufficiently capture the interfacial effects of an inclusion-matrix system. By using nano-scale material descriptions, nucleation lattice strains are obtained which are in good agreement with previous experimental studies. The motivation for Chapter 4 stems from a recognized need to develop a method for modeling corrosion behaviour of materials. Corrosion is also an issue for reactor design and an ability to predict failure points is needed. Finite element models could be used for this purpose, provided model accuracy is verified first. In Chapter 4 a technique is developed which facilitates the extraction of sub-micron resolution strain data from correlation images obtained during in-situ tensile deformation. By comparing image correlation results with a crystal plasticity finite element code it is found that good agreement between the two exists. The method outlined is material independent and could be applied to most metallurgical studies. Chapter 5 reviews the findings of each case study and makes suggestions as to the direction of future research.
Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-09-30 16:05:52.934

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(7543412), Kartik Kapoor. „EXPERIMENTALLY VALIDATED CRYSTAL PLASTICITY MODELING OF TITANIUM ALLOYS AT MULTIPLE LENGTH-SCALES BASED ON MATERIAL CHARACTERIZATION, ACCOUNTING FOR RESIDUAL STRESSES“. Thesis, 2019.

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There is a growing need to understand the deformation mechanisms in titanium alloys due to their widespread use in the aerospace industry (especially within gas turbine engines), variation in their properties and performance based on their microstructure, and their tendency to undergo premature failure due to dwell and high cycle fatigue well below their yield strength. Crystal plasticity finite element (CPFE) modeling is a popular computational tool used to understand deformation in these polycrystalline alloys. With the advancement in experimental techniques such as electron backscatter diffraction, digital image correlation (DIC) and high-energy x-ray diffraction, more insights into the microstructure of the material and its deformation process can be attained. This research leverages data from a number of experimental techniques to develop well-informed and calibrated CPFE models for titanium alloys at multiple length-scales and use them to further understand the deformation in these alloys.

The first part of the research utilizes experimental data from high-energy x-ray diffraction microscopy to initialize grain-level residual stresses and capture the correct grain morphology within CPFE simulations. Further, another method to incorporate the effect of grain-level residual stresses via geometrically necessary dislocations obtained from 2D material characterization is developed and implemented within the CPFE framework. Using this approach, grain level information about residual stresses obtained spatially over the region of interest, directly from the EBSD and high-energy x-ray diffraction microscopy, is utilized as an input to the model.

The second part of this research involves calibrating the CPFE model based upon a systematic and detailed optimization routine utilizing experimental data in the form of macroscopic stress-strain curves coupled with lattice strains on different crystallographic planes for the α and β phases, obtained from high energy X-ray diffraction experiments for multiple material pedigrees with varying β volume fractions. This fully calibrated CPFE model is then used to gain a comprehensive understanding of deformation behavior of Ti-6Al-4V, specifically the effect of the relative orientation of the α and β phases within the microstructure.

In the final part of this work, large and highly textured regions, referred to as macrozones or microtextured regions (MTRs), with sizes up to several orders of magnitude larger than that of the individual grains, found in dual phase Titanium alloys are modeled using a reduced order simulation strategy. This is done to overcome the computational challenges associated with modeling macrozones. The reduced order model is then used to investigate the strain localization within the microstructure and the effect of varying the misorientation tolerance on the localization of plastic strain within the macrozones.

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Yang, Jie. „Simulation modeling for the impact of triage liaison physician on emergency department to reduce overcrowding“. 2017. http://hdl.handle.net/1993/31963.

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Emergency department (ED) overcrowding has been a common complaint in Emergency Medicine in Canada for many years. Its adverse effects of prolonged waiting times cause patient dissatisfaction and unsafety. Previous studies indicate that adding a physician in triage (PIT) can increase accuracy and efficiency in the initial process of patient evaluation. However, the scientific evidence of the PIT impact on ED is far away from sufficient before its widespread implementation. This research is to search solutions using PIT to identify areas of improvement for the ED patient flow, based upon a validated discrete-event simulation (DES) model. As an efficient decision-making tool, the DES model also helps to develop an understanding of the current ED performance and quantitatively test various design alternatives for ED operations.
February 2017

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Buchteile zum Thema "Reduced Length Modeling"

Kiehl, M. „Increasing the Vector Length for Matrix Multiplication with Reduced Memory Access“. In Mathematical Modelling and Simulation of Electrical Circuits and Semiconductor Devices, 101–8. Basel: Birkhäuser Basel, 1990. http://dx.doi.org/10.1007/978-3-0348-5698-0_8.

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Tiwari, Ritu, Anupam Shukla und Rahul Kala. „Hybrid Evolutionary Methods“. In Rapid Automation, 295–336. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-8060-7.ch014.

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The limitations of single algorithm approaches lead to an attempt to hybridize or fuse multiple algorithms in the hope of removing the underlying limitations. In this chapter, the authors study the evolutionary algorithms for problem solving and try to use them in a unique manner so as to get a better performance. In the first approach, they use an evolutionary algorithm for solving the problem of motion planning in a static environment. An additional factor called momentum is introduced that controls the granularity with which a robotic path is traversed to compute its fitness. By varying the momentum, the map may be treated finer or coarser. The path evolves along the generations, with each generation adding to the maximum possible complexity of the path. Along with complexity (number of turns), the authors optimize the total path length as well as the minimum distance from the obstacle in the robotic path. The requirement of evolutionary parameter individuals as well as the maximum complexity is less at the start and more at the later stages of the algorithm. Momentum is made to decrease as the algorithm proceeds. This makes the exploration vague at the start and detailed at the later stages. As an extension to the same work, in the second approach of the chapter, the authors show the manner in which a hybrid algorithm may be used in place of simple genetic algorithm for solving the problem with momentum. A Hybrid Genetic Algorithm Particle Swarm Optimization (HGAPSO) algorithm, which is a hybrid of a genetic algorithm and particle swarm optimization, is used in the same modeling scenario. In the third and last approach, the authors present a hierarchical evolutionary algorithm that operates in two hierarchies. The coarser hierarchy finds the path in a static environment consisting of the entire robotic map. The resolution of the map is reduced for computational speed. The finer hierarchy takes a section of the map and computes the path for both static and dynamic environments. Both these hierarchies carry optimization as the robot travels in the map. The static environment path gets more and more optimized along with generations. Hence, an extra setup cost is not required like other evolutionary approaches. The finer hierarchy makes the robot easily escape from the moving obstacle, almost following the path shown by the coarser hierarchy. This hierarchy extrapolates the movements of the various objects by assuming them to be moving with same speed and direction.

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Dickerson, Keith, David Faulkner, Nigel Wall und Simon Watts. „Environmental Assessment of Hybrid Broadband Satellite Systems“. In Green Services Engineering, Optimization, and Modeling in the Technological Age, 192–222. IGI Global, 2015. http://dx.doi.org/10.4018/978-1-4666-8447-8.ch008.

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This chapter describes the environmental assessment of hybrid broadband satellite systems using the latest lifecycle analysis (LCA) techniques. The BATS (Broadband Access via integrated Terrestrial and Satellite systems) project has based its assessments on the GHG Protocol approach, with the ETSI LCA and ITU-T L.1400 methodology series used to provide more detailed guidance where this is needed. This assessment has shown that it is possible to employ cut off rules and approximations to reduce the cost or length of an assessment and still provide useful results. The assessment has shown that, using current technology for the IUG and satellite modem, the carbon footprint of a hybrid broadband satellite network can be comparable with that of a terrestrial (fixed or mobile) network for an equivalent level of service when the use of low-power states are considered. The implementation of these states in future commercial systems should be explored. Finally ways are suggested to reduce the environmental impact of hybrid broadband satellite systems, in particular by reducing energy (power) consumption during the use stage. Key issues include how to compare the energy efficiency of a hybrid broadband satellite network with other methods of broadband delivery, how to accurately assess the carbon embodied during the production of the equipment, and how to use low-power modes to reduce energy consumption without affecting the response time or quality of experience (QoE).

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Abelha, Vasco, Fernando Marins und Henrique Vicente. „Evaluation of the Length of Hospital Stay through Artificial Neural Networks Based Systems“. In Applying Business Intelligence to Clinical and Healthcare Organizations, 153–68. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-4666-9882-6.ch008.

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The mentality of savings and eliminating any kind of outgoing costs is undermining our society and our way of living. Cutting funds from Education to Health is at best delaying the inevitable “Crash” that is foreshadowed. Regarding Health, a major concern, can be described as jeopardize the health of Patients – Reduce of the Length of Hospital. As we all know, Human Health is very sensitive and prune to drastic changes in short spaces of time. Factors like age, sex, their ambient context – house conditions, daily lives – should all be important when deciding how long a specific patient should remain safe in a hospital. In no way, ought this be decided by the economic politics. Logic Programming was used for knowledge representation and reasoning, letting the modeling of the universe of discourse in terms of defective data, information and knowledge. Artificial Neural Networks and Genetic Algorithms were used in order to evaluate and predict how long should a patient remain in the hospital in order to minimize the collateral damage of our government approaches, not forgetting the use of Degree of Confidence to demonstrate how feasible the assessment is.

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Abelha, Vasco, Fernando Marins und Henrique Vicente. „Evaluation of the Length of Hospital Stay Through Artificial Neural Networks Based Systems“. In Hospital Management and Emergency Medicine, 391–403. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-2451-0.ch020.

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Konferenzberichte zum Thema "Reduced Length Modeling"

Ghosh, Rajat, und Yogendra Joshi. „Dynamic Reduced Order Thermal Modeling of Data Center Air Temperatures“. In ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/ipack2011-52029.

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We developed a Proper Orthogonal Decomposition (POD) based dynamic reduced order model that can predict transient temperature field in an air-cooled data center. A typical data center is modeled as a turbulent convective thermal system with multiple length scales. A representative case study is presented to validate the developed methodology. The model is observed to be capable of predicting the transient air temperature field accurately and rapidly. Comparing with the computational fluid mechanics/heat transfer (CFD/HT) based model, it is revealed that our model is 100x faster without compromising solution accuracy. The developed modeling framework is potentially useful for designing a control system that can regulate flow parameters in a transient data center.

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Joshi, Yogendra. „Reduced Order Thermal Models of Multi-Scale Microsystems“. In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-23373.

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Thermal systems often involve multiple spatial and temporal scales, where transport information from one scale is relevant at others. Optimized thermal design of such systems and their control require approaches for their rapid simulation. These activities are of increasing significance due to the need for energy efficiency in the operation of these systems. Traditional full-field simulation methodologies are typically unable to resolve these scales in a computationally efficient manner. We handle the simulations of conjugate transport processes over selected length scales of interest via reduced order modeling through approaches such as compact finite elements, and proper orthogonal decomposition. In order to incorporate the influence of length scales beyond these, lumped models are invoked, with appropriate handshaking between the two frameworks. We illustrate the methodology through selected examples, with a focus on information technology systems.

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Cranford, E. Lyles, Mark A. Gray und Rashed Kabir. „Reduced Life Cycles Cost and Improved Analysis Accuracy Utilizing WESTEMS™ Integrated Modeling Methods“. In ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1325.

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Traditional methods of qualifying pressure vessel components to ASME stress and fatigue requirements often involve complex and lengthy calculation processes. The costs of individually analyzing every specified transient can be prohibitive if large numbers of transients are considered, with each one having varied loading conditions acting on the components. In addition, the time dependent nature of real transient loads results in a significant computational and bookkeeping problem. In most cases the analyst uses a number of simplifying and enveloping assumptions to develop stresses to represent all transient conditions. He relies on his experience and judgment to make simplifications with respect to the timing of applied mechanical loads, as well as the relationship between the applied mechanical loads and the timing of the thermal loads. The analyst’s skill governs the length and complexity of the qualification process. The WESTEMS™ Integrated Modeling approach dramatically simplifies this effort and improves analysis accuracy, while reducing the overall time necessary to perform the analysis. WESTEMS™ Integrated Models can reduce the process of analyzing a list of transients defined by global parameter time histories and reporting final design stress and fatigue to a few steps. This paper discusses how WESTEMS™ overcomes the technical difficulties encountered in automating such tasks, and shows the technical superiority of WESTEMS™ over the current traditional methods. It also demonstrates how applying the WESTEMS™ technology to NSSS equipment can reduce engineering life cycle costs.

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Muñoz, Hiram Martinez. „Analysis of Errors in Simulation Modeling“. In HT2021. ASM International, 2021. http://dx.doi.org/10.31399/asm.cp.ht2021exabp0053.

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Abstract Nowadays, the use of technologies to increase productivity, reduce time, as well as reduce the possibilities of errors, has become indispensable. All processes have opportunities for improvement, and this can be done based on calculations that with the support of computational systems can be reduced considerably in time. In the heat treatment industry and more specifically in the electromagnetic induction heat treatment industry is no exception. Today we have numerous tools to optimize the design process of inductors used in heat treatment of metals. These tools can show us, in a virtual way, the results that we can obtain before having to manufacture the inductors, all this based on FEA (Finite Elements Analysis) simulations that performing calculations considering physical parameters approximate us to what we would have as a result. Computer based simulation programs for induction heating and resulting metallurgy are extremely useful in developing tooling and process for induction heating. Induction hardening simulation brings elements of inductor design, steel properties such as time-temperature-transformation curves, both thermal and magnetic properties at various temperatures and cooling rates based on the phase of the quench media on cooling. A common method in place hardening (static hardening) knows as single shot hardening. In this process, the inductor is designed with a top and bottom half loop connected by heating rails. The length of heating is determined by the length of the rails and percentage height of the width of the half loops. Accurately predicting the length of the heating pattern in this 3D modeling approach is computationally a heavy load on the modeling pre-requisites. Commonly the inductor is modeled and then tested with the actual results showing a different length than what was predicted. It is important to consider that like any system, these simulation tools are not infallible and have several factors that can affect the accuracy of the simulation results. This paper reaches into the analysis of why the predicted length may differ prom the test results discussing what factors constitute the largest variance from the predicted outcome. Inductor design and the reliance on set up will be discussed.

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Mandel, Raphael, Amir Shooshtari, Serguei Dessiatoun und Michael Ohadi. „Streamline Modeling of Manifold Microchannels in Thin Film Evaporation“. In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17731.

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Manifold microchannels utilize a system of manifolds to divide long microchannels into an array of parallel ones, resulting in reduced flow length and more localized liquid feeding. Reducing flow length is desirable because it enables the simultaneous enhancement of heat transfer rate and reduction of pressure drop. Furthermore, localized feeding reduces potential for localized dryout, increasing the operational heat flux. Because of the failure of the available conventional heat transfer correlations to predict the thermal performance of manifold microchannels operating in two phase mode, a “streamline” model was created. The heat transfer surface area was divided into parallel, non-interacting streamlines, and the quality, void fraction, film thickness, heat transfer coefficient, heat flux, and pressure drop was calculated sequentially along the streamline. The mass flow rate through each streamline was adjusted in order to obtain the specified pressure drop, and the value of this pressure drop was adjusted in order to obtain the desired microchannel mass flux. Finally, the average wall heat transfer coefficient was calculated, and temperature profile in the fin was adjusted to correspond with the analytical 1-D temperature distribution of a thin fin with an average wall heat transfer coefficient and specified base superheat. The average wall heat transfer coefficients predicted by the model was then compared to the available experimental data with sufficiently good agreement with a wide variety of geometries and working fluids at low mass fluxes.

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Sheppard, S. D., D. J. Wilde und Y. L. Hsu. „Algebraic Acceleration of Finite Element Optimization; Four Modeling Errors in a Weldment Design“. In ASME 1989 Design Technical Conferences. American Society of Mechanical Engineers, 1989. http://dx.doi.org/10.1115/detc1989-0063.

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Abstract A method is proposed for incorporating finite element stress analysis into the constraints of an optimization model. To reduce the number of computationally intensive finite element analyses, the more accurate FEA plate model is approximated by an algebraic beam model having an adjustable factor whose value is determined by comparing FEA stresses with the corresponding beam theory predictions. This factor compensates both for the inaccuracies of beam theory and the effect of stress concentration. The algebraic form is retained to permit application of powerful optimization techniques not applicable directly to finite element models. The optimization problem is thus reduced to the determination of the single factor by linear interpolation. When tested on Keith’s well-known welded cantilever problem, the method needs only three FEAs. Keith’s model is also shown to suffer from four errors, of which three are remedied here. Because of special problem structure, the resulting design is correct for three of the four design variables, but the length of the weld cannot be determined without a better weld stress model.

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Kamrani Fard, Kiana, und James A. Liburdy. „Discrete Vortex Modeling of a Flapping Foil Energy Harvester With LEV Shedding Criterion“. In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-24216.

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Abstract The energy harvesting performance of a flapping airfoil is studied through discrete vortex model. Results are obtained for a thin flat airfoil that undergoes a sinusoidal flapping motion for reduced frequencies of k = fC/U∞ = 0.06–0.16 where f is the heaving frequency of the foil, C is the chord length and U∞ is the freestream velocity. The airfoil pitches about the mid-chord and the heaving and pitching amplitudes of the airfoil are h0 = 0.5C and θ0 = 70° respectively, as these numbers have been shown to give optimal energy harvesting results for a rigid airfoil. The study applies a panel-based discrete vortex model that incorporates a leading edge suction parameter criterion to understand the flow behavior around the airfoil. The leading edge suction parameter is found from 2D CFD simulations (Navier-Stokes equations solved in Fluent) for all K values. A correlation between the critical leading edge suction parameter and reduced frequency is found from the identified critical LESP values. An empirical trailing edge separation correction is also applied to the transient force results since flow separation at the trailing edge is anticipated. The parameters of interest from the model are transient distributions of force, power output, and overall efficiency. Model results are then validated against 2D CFD simulations. The effect of reduced frequency on power production and overall efficiency is finally studied to identify the optimal reduced frequency for energy harvesting applications.

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Ouakad, Hassen M., und Mohammad I. Younis. „Modeling and Simulations of Collapse Instabilities of Microbeams Due to Capillary Forces“. In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67502.

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We present modeling and analysis for the static behavior and collapse instabilities of doubly-clamped and cantilever microbeams subjected to capillary forces. These forces can be as a result of a volume of liquid trapped underneath the microbeam during the rinsing and drying process in fabrication. The model considers the microbeam as a continuous medium, the capillary force as a nonlinear function of displacement, and accounts for the mid-plane stretching nonlinearity. The capillary force is assumed to be distributed over a specific length underneath the microbeam. The Galerkin procedure is used to derive a reduced-order model consisting of a set of nonlinear algebraic and differential equations that describe the microbeams static and dynamic behaviors. We study the collapse instability, which brings the microbeam from its unstuck configuration to touch the substrate and gets stuck in the so-called pinned configuration. We calculate the pull-in length that distinguishes the free from the pinned configurations as a function of the beam thickness and gap width for both microbeams. Comparisons are made with analytical results reported in the literature based on the Ritz method for linear and nonlinear beam models. The instability problem, which brings the microbeam from a pinned to adhered configuration is also investigated. For this case, we use a shooting technique to solve the boundary-value problem governing the deflection of the microbeams. The critical microbeam length for this second instability is also calculated.

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Salakij, Saran, James A. Liburdy und Deborah V. Pence. „Modeling In-Situ Vapor Extraction During Convective Boiling“. In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78522.

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The pressure drop of convective boiling flow may be reduced by extracting vapor locally since the entire generated vapor does not have to travel through the entire channel length. In this study, the theoretical model was developed to simulate a convective boiling flow through a fractal-like branching microchannel network with vapor extraction. The fractal-like branching microchannel network has a porous membrane forming one wall of the channels. Vapor extraction occurs by applying a vacuum across the membrane. Sample predictive local conditions and global results are presented and discussed. The predicting results are classified into two groups: low inlet flow rate-low heat flux and high inlet flow rate-high heat flux. The results show that to increase extracted vapor mass flow rate, either decreasing supplying extracting pressure or increasing permeability of the porous membrane must be applied. As the amount of vapor extracting increases, the reduction in pressure drop across the channel and the exit vapor quality is achieved.

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Miler, Josef L., Gamal Refai-Ahmed, Maxat N. Touzelbaev, Milnes P. David, Julie E. Steinbrenner und Kenneth E. Goodson. „Reduced-Order Fluidic Model for Flow Instabilities in Two-Phase Microfluidic Heat Exchangers“. In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30878.

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Two-phase microfluidic heat exchangers have the potential to provide high-heat flux cooling with lower thermal resistance and lower pumping power than single-phase heat exchangers. However, the process of phase change in two-phase heat exchangers can cause flow instabilities that lead to microchannel dryout and device failure [1–3]. Modeling these flow instabilities remains challenging because the key physics are highly coupled and occur over disparate time and length scales. This work introduces a new approach to capture transient thermal and fluidic transport with a reduced-order model consisting of fluidic, thermal, and phase-change submodels. The present study presents a reduced-order, transient, multichannel fluidic circuit submodel for integration into this proposed modeling approach. The fluidic submodel is applicable in flow regimes in which a thin liquid film exists around the bubble. Flow response to boiling is modeled considering bubble overpressure. An adaptive time step approach is used to treat the rapid flow response at short time scales after initial bubble vaporization. Using a seeded bubble technique for testing two-phase flow response, the model predicts a stability threshold at 0.015 W of localized superheating for two 100-micron square channels in parallel with a pump flow rate of 0.15 ml/min. Once integrated with the proposed reduced-order thermal and phase change models, this fluidic circuit model will yield criteria for stable two-phase heat exchanger operation considering factors such as pumping pressure, channel geometry, and applied heat flux that can be compared to experimental observations.

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