scholarly journals A COMPARISON OF DIFFERENT NUMERICAL APPROACHES FOR FSW WELDS OF API 5L - X80 STEEL

2020 ◽  
Vol 5 (6) ◽  
Author(s):  
Guilherme Gadelha de Sousa Figueiredo ◽  
Igor Jordão Marques ◽  
Tiago Felipe De Abreu Santos
Keyword(s):  
Thermal Model ◽  
Fluid Dynamic ◽  
Numerical Approach ◽  
Physical Constants ◽  
High Temperature Materials ◽  
Welding Line ◽  
X80 Steel ◽  
Experimental Values ◽  
Material Temperature ◽  
Numerical Approaches

This contribution offers a study for two numerical approaches of FSW joints for the API 5L-X80 steel. The first one, a pure thermal model, takes into consideration the preponderant frictional force of the tool being in contact with the workpiece. The second model is a computational fluid dynamic approach, which involves determining experimental values for physical constants and observing its influence in viscous dissipation and strain rates of the material. Temperature and thermal history from the FSW processing were recorded and analyzed. The acquired data was provided from two different heat input conditions. In cases of previewing tool or workpiece local temperature, the pure thermal model is a sufficient suitable approach. Conversely, the CFD model frequently requires huge amounts of information, regarding physical constants and experimental variables, becoming a delicate task for its construction. The pure thermal model was able to offer unequivocal temperature results without the need for large experimental data acquisition. This approach was considered to be finer employed when one aims to forecast temperatures in regions proximate to the welding line. The natural complexity associated with FSW processing suggests there are enormous quantities of experimental factors to be considered for the numerical modeling of high-temperature materials. Also, the CFD approach offers distinct results, which might be crucial for understanding the full aspects of experimental variables. A coupled numerical approach with both models is suggested to fully represent the thermophysical aspects of FSW processing.

scholarly journals Hybrid Analytical and Numerical Approach for Modeling Fluid Flow in Simplified Three-Dimensional Fracture Networks

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
D. Roubinet ◽  
S. Demirel ◽  
E. B. Voytek ◽  
X. Wang ◽  
J. Irving
Keyword(s):  
Fluid Flow ◽  
Three Dimensional ◽  
Fracture Network ◽  
Numerical Approach ◽  
Fracture Networks ◽  
Surrounding Matrix ◽  
Mesh Free ◽  
Fracture Scale ◽  
The Impact ◽  
Numerical Approaches

Modeling fluid flow in three-dimensional fracture networks is required in a wide variety of applications related to fractured rocks. Numerical approaches developed for this purpose rely on either simplified representations of the physics of the considered problem using mesh-free methods at the fracture scale or complex meshing of the studied systems resulting in considerable computational costs. Here, we derive an alternative approach that does not rely on a full meshing of the fracture network yet maintains an accurate representation of the modeled physical processes. This is done by considering simplified fracture networks in which the fractures are represented as rectangles that are divided into rectangular subfractures such that the fracture intersections are defined on the borders of these subfractures. Two-dimensional analytical solutions for the Darcy-scale flow problem are utilized at the subfracture scale and coupled at the fracture-network scale through discretization nodes located on the subfracture borders. We investigate the impact of parameters related to the location and number of the discretization nodes on the results obtained, and we compare our results with those calculated using reference solutions, which are an analytical solution for simple configurations and a standard finite-element modeling approach for complex configurations. This work represents a first step towards the development of 3D hybrid analytical and numerical approaches where the impact of the surrounding matrix will be eventually considered.

The Role of Simulation in the Development of a Fast-Actuation Solenoid C.R. Injection System

2004 ◽  
Author(s):  
Gian Marco Bianchi ◽  
Piero Pelloni ◽  
Giovanni Osbat ◽  
Marco Parotto ◽  
Rita Di Gioia ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Control Strategies ◽  
Fluid Dynamic ◽  
Numerical Approach ◽  
Linear Analysis ◽  
Operating Conditions ◽  
System Model ◽  
Injection System ◽  
Multiple Injection ◽  
Pressure Regulator

Upcoming Euro 4 and Euro 5 emission standards are increasing efforts on injection system developments in order to improve mixture quality and combustion efficiency. The target features of advanced injection system are related to their capability of operating multiple injection with a precise control of amount of fuel injected, low cycle-by-cycle variability and life drift, within flexible strategies. In order to accomplish this task, performance must be optimised since injection system concept development by acting on. The extensive use of numerical approach has been identified as a necessary integration to experiments in order to put on the market high quality injection system accomplishing strict engine control strategies. The modelling approach allows focusing the experimental campaign only on critical issues saving time and costs, furthermore it is possible to deeply understand inner phenomena that cannot be measured. The lump/ID model of the whole system built into the AMESim® code was presented in previous works: particular attention was devoted in the simulation of the electromagnetic circuits, actual fluid-dynamic forces acting on needle surfaces and discharge coefficients, evaluated by means 3D-CFD simulations. In order to assess new injection system dynamic response under multiple injection strategies reproducing actual engine operating conditions it is necessary to find to proper model settings. In this work the integration between the injector and the system model, which comprehends the pump, the pressure regulator, the rail and the connecting-pipes, will be presented. For reproducing the dynamic response of he whole system will be followed a step-by-step approach in order to prevent modelling inaccuracies. Firstly will be presented the linear analysis results performed in order to find injection system own natural frequencies. Secondly based on linear analysis results will be found proper injection system model settings for predicting dynamic response to external excitations, such as pump perturbations, pressure regulator dynamics and injection pulses. Thirdly experimental results in terms of instantaneous flow rate and integrated injected volume for different operating conditions will be presented in order to highlight the capability of the modelling methodology in addressing the new injection system design.

scholarly journals Numerical Fatigue Analysis of a Prototype Francis Turbine Runner in Low-Load Operation

2019 ◽  
Vol 4 (3) ◽  
pp. 21 ◽  
Author(s):  
Julian Unterluggauer ◽  
Eduard Doujak ◽  
Christian Bauer
Keyword(s):  
Fatigue Damage ◽  
Power Plants ◽  
Response Times ◽  
Fluid Dynamic ◽  
Numerical Approach ◽  
Fast Response ◽  
Francis Turbine ◽  
Hydro Power ◽  
Hydraulic Machines ◽  
Low Load

Depending on a dynamical energy market dominated by the influence of volatile energies, the operators of hydro-power plants are forced to extend the operating range of their hydraulic machines to stay competitive. High flexibility towards low-load, a rising number of start-ups and fast response times are required for better control of the electrical grid. The major downside of these operating regions is that pressure pulsations, which are induced by the means of flow phenomena, lead to higher fatigue damage regarding the runner. Therefore, site measurements in combination with numerical methods can be used to gain a deeper understanding of the runner lifetime. This paper presents a numerical approach to understand the critical operation zones and access fatigue damage, including steady state, unsteady and transient computational fluid dynamic (CFD) one-way coupled with a transient finite element method (FEM).

Geometrical Evaluation of a Pair of Elliptical Tubes Subjected to a Flow with Forced Convection Heat Transfer

2019 ◽  
Vol 396 ◽  
pp. 155-163
Author(s):  
Ana Paula Del Aghenese ◽  
Eliander Manke Heinemann ◽  
Gabriel de Avila Barreto ◽  
Filipe Branco Teixeira ◽  
Liércio André Isoldi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Degrees Of Freedom ◽  
Fluid Dynamic ◽  
Convection Heat Transfer ◽  
Numerical Approach ◽  
Angle Of Incidence ◽  
Prandtl Numbers ◽  
Forced Convective Flow ◽  
Volume Method

In the present work it is performed a study on the geometric evaluation of a pair of elliptical tubes subjected to external flow with forced convection by means of numerical approach. The objectives are the maximization of Nusselt number (NuD) and the minimization of drag coefficient (CD). The degrees of freedom for the pair of tubes arrangement are: the ratio between the transverse pitch and characteristic length of tubes (ST/D), where D = (A)1/2, the ratio of the main and secondary axes of the elliptical tube (a/b) and the angle of incidence of the flow on the pair of tubes (α). The simulations were carried out considering two-dimensional forced convective flows, in the laminar regime and incompressible conditions. For all configurations, Reynolds and Prandtl numbers are constant, ReD = 100 and Pr = 0.71. The Finite Volume Method (FVM) is used to solve conservation equations of mass, momentum and energy. The software Gmsh is used for creation of the geometries and generation of the meshes. Results showed that the degrees of freedom affected the fluid dynamic and thermal performance of the forced convective flow. According to the objectives outlined in this study, the best performance for the maximization of heat transfer was obtained when α = 0o, a/b = 1⁄2 and ST/D = 3.5. In the case of the fluid dynamics study, the optimal result for CD minimization occurred when α = 0o, a/b = 2.0 and ST/D = 4.0. Thus, the optimal geometry will depend on the indicator performance where the problem is evaluated.

Numerical Investigation on the Heat Transfer Enhancement due to Coolant Extraction on the Cold Side of Film Cooling Holes

2014 ◽  
Author(s):  
A. Andreini ◽  
G. Caciolli ◽  
R. Da Soghe ◽  
B. Facchini ◽  
L. Mazzei
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Fluid Dynamic ◽  
Numerical Approach ◽  
Test Case ◽  
Cold Side ◽  
Engine Design ◽  
Starting Point ◽  
Sst Model ◽  
Film Cooling Holes

Film cooling represents one the most widely-used cooling techniques for hot gas path components. In particular, effusion cooling has recently become an important focus of attention in the context of aero-engine design due to its high cooling performance. Notwithstanding the huge amount of work dedicated to the heat transfer on the hot side of effusion cooling plates, it has been demonstrated that up to 30 % of the total cooling effectiveness of a typical effusion cooling configuration can be ascribed to cold side convective cooling. Nevertheless, in open literature it is possible to notice a lack of knowledge as far as this topic is concerned. This paper describes a numerical activity aimed at investigating the phenomenology of the heat transfer at the entrance of film cooling holes. First of all the accuracy of the numerical approach has been validated through a comparison of enhancement factor measurements on a test case available in literature. Steady state RANS simulations have been performed, modeling turbulence by means of the k–ω SST model. The use of a transition model has been taken into account, since in these configurations the transitional behavior of the boundary layer has been highlighted in literature. Subsequently, the attention has been turned to the comprehension of the phenomena involved in the heat transfer augmentation, focusing the attention to the influence of fluid dynamic parameters such as suction ratio and Reynolds number. A good agreement has been highlighted with experimental data, therefore this work provides a starting point for future investigations on more representative configurations.

scholarly journals An analytical and numerical approach to a bilateral contact problem with nonmonotone friction

2013 ◽  
Vol 23 (2) ◽  
pp. 263-276 ◽  
Author(s):  
Mikaël Barboteu ◽  
Krzysztof Bartosz ◽  
Piotr Kalita
Keyword(s):  
Contact Problem ◽  
Frictional Contact ◽  
Numerical Approach ◽  
Bundle Method ◽  
Nonconvex Problem ◽  
Proximal Bundle Method ◽  
Loss Of Contact ◽  
The Galerkin Method ◽  
Bilateral Contact ◽  
Numerical Approaches

We consider a mathematical model which describes the contact between a linearly elastic body and an obstacle, the so-called foundation. The process is static and the contact is bilateral, i.e., there is no loss of contact. The friction is modeled with a nonmotonone law. The purpose of this work is to provide an error estimate for the Galerkin method as well as to present and compare two numerical methods for solving the resulting nonsmooth and nonconvex frictional contact problem. The first approach is based on the nonconvex proximal bundle method, whereas the second one deals with the approximation of a nonconvex problem by a sequence of nonsmooth convex programming problems. Some numerical experiments are realized to compare the two numerical approaches.

Numerical Approach for the Evaluation of Seam Welding Criteria in Extrusion Processes

2012 ◽  
Vol 504-506 ◽  
pp. 517-522 ◽  
Author(s):  
Martin Schwane ◽  
Thomas Kloppenborg ◽  
Andreas Reeb ◽  
Nooman Ben Khalifa ◽  
Alexander Brosius ◽  
...  
Keyword(s):  
Automobile Industry ◽  
Numerical Approach ◽  
Extrusion Process ◽  
Experimental Investigations ◽  
Welding Quality ◽  
Seam Welding ◽  
Numerical Investigations ◽  
Welding Line ◽  
Aluminum Profiles ◽  
Longitudinal Seam

The accurate simulation and the optimization of extrusion processes can be a helpful technique to ensure producibility of complex aluminum profiles, for example for the automobile industry. Currently, the die designing is based on expert’s knowledge and cost-intensive prototyping. The paper deals with numerical investigations based on finite element simulations as well as experimental investigations of an industrial extrusion process. A newly developed method for longitudinal seam weld prediction is applied to analyze the position of the longitudinal welding line and the welding quality.

Turbomachinery Modeling: Explicit and Impliit Knowledge Capturing (2005A)

2005 ◽  
Author(s):  
David Japikse ◽  
Kerry N. Oliphant
Keyword(s):  
Fluid Dynamic ◽  
Model Development ◽  
Numerical Approach ◽  
Performance Models ◽  
Physical Relationship ◽  
Fully Integrated ◽  
Axial Compressors ◽  
Design Engineers ◽  
Axial Turbines ◽  
Optimization Search

Design engineers rely on quality performance models to establish the physical relationship between diverse thermodynamic, geometric, and fluid dynamic parameters that govern turbomachinery performance. If these models are based on a rigorous, scientific foundation, they permit the designer to thoroughly optimize a new configuration and establish with confidence the performance levels to be expected when the product is introduced in the market. The process of developing advanced models has endured more than a full century, and models of increased complexity have been introduced. However, many aspects of model development have not received thorough scientific evaluation. In the turbomachinery field, meanline performance models for axial turbines have been well developed and widely published; nearly the same can be said for the field of axial compressors. Beyond these two examples, there is a need for more model development and improvement, particularly emphasizing radial and mixed-flow turbomachines. This paper shows a systematic method, now fully integrated into a computerized methodology with optimization search techniques, for extracting the greatest useful knowledge from diverse datasets suitable for subsequent model development. The process focuses on modeling eight dependent variables based on five or six independent variables that have been found to be essential for understanding the performance of these machines. This paper emphasizes the scientific and numerical approach taken to process the data such that advanced models can be developed. The actual model development is presented in subsequent papers.

Theoretical and Numerical Approaches for Calculating the Performances of an Industrial Turboshaft

2014 ◽  
Vol 555 ◽  
pp. 121-126 ◽  
Author(s):  
Jeni Alina Popescu ◽  
Valeriu Vilag ◽  
Cleopatra Florentina Cuciumita ◽  
Valentin Silivestru
Keyword(s):  
Gas Turbine ◽  
Output Power ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Thermodynamic Cycle ◽  
Numerical Approach ◽  
Numerical Code ◽  
Operating Cycle ◽  
Future Work ◽  
Numerical Approaches

The paper presents two approaches for the thermodynamic cycle analysis applied to gas turbines. For a 1,500 kW industrial engine, still in development, different configurations are considered, the most complex including intercooling and heat recovery components. The theoretical algorithm, a conventional compromise between simplicity and accuracy, is presented in the first part of the paper. The second part describes a numerical approach for calculating the operating cycle of a gas turbine and presenting the methods for preparing the particular required format. The conclusions are related to the future work necessary for finalizing a numerical code able to analyse different gas cycle options allowing to obtain the desired output power and efficiency.

Combined Experimental - Numerical Approach for the Fuel Jet Study in a LPP Combustor

2011 ◽  
Author(s):  
Amedeo Amoresano ◽  
Maria Cristina Cameretti ◽  
Raffaele Tuccillo
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Numerical Approach ◽  
Experimental Information ◽  
Liquid Fuels ◽  
Injection System ◽  
Spray Parameters ◽  
Flow Solver ◽  
Fuel Jet ◽  
Fuel Vapour

The purpose of the paper is the investigation of the phenomena that mainly affect the mixture preparation and the combustion development in lean-premixed chambers supplied with liquid fuels (LPP). In such a study, the experimental analysis, performed by PDA based measurements, is supported and addressed by a CFD tool that is able to simulate the injection conditions, by isolating and studying some specific phenomena. A 3-D fluid dynamic code (i.e., the FLUENT® flow solver) has been used to simulate the spray pattern in the chamber. Preliminarily, the numerical simulation refer to cold flow conditions, in order to validate the estimation of the fundamental spray parameters through the comparison with the experimental data; in a second step, the calculations employ boundary conditions close to those occurring in the actual combustor operation, in order to predict the fuel vapour distribution throughout the premixing chamber. In particular, the fuel is injected under the typical conditions that occur in the injection system of a gas turbine LPP combustor. In this phase, the experimental information are introduced in terms of air and fuel mass flow rates and of inlet characteristics of the air flow entering the prevaporizing chamber, in order to predict the fuel vapour formation and distribution. The paper also compares different approaches that have been experienced for the CFD simulation.

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