Model Uncertainty in Fluid-Structure Impact Risk Analysis

2006 ◽  
Author(s):  
Kenneth N. Mitchell ◽  
Sankaran Mahadevan
Keyword(s):  
Model Uncertainty ◽  
Space Shuttle ◽  
Experimental Testing ◽  
Model Verification ◽  
Risk Assessments ◽  
Analysis Model ◽  
Element Discretization ◽  
Fluid Structure ◽  
Systematic Assessment ◽  
Impact Problems

This paper investigates the issue of model uncertainty in risk assessments of fluid-structure impact problems. Model-based risk assessments of complex phenomena such as the space shuttle solid rocket booster (SRB) splashdown event is affected by significant model uncertainty and approximations in finite element discretization, damage modeling, and the probabilistic analysis. Model verification and validation (V&V) helps in systematic assessment of modeling error, and suitable V&V techniques are explored in this paper. Since experimental testing of the SRB is infeasible, a simplified experimental framework is devised using an aluminum cylinder hinged at one end, with the objective of providing insights into the required model form (validation) as well as the required model resolution (verification). Preliminary results from error quantification as well as experimental validation are presented and discussed. Such information could be used to develop confidence and credibility in real-world reliability predictions of fluid-structure impact problems such as SRB splashdown.

scholarly journals Construction of Spatiotemporal Difference Image of the Impact of Financial Structure on China’s Total Factor Productivity

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Yong Yu
Keyword(s):  
Total Factor Productivity ◽  
Evaluation Method ◽  
Financial Structure ◽  
Model Verification ◽  
Factor Productivity ◽  
Analysis Model ◽  
Dea Model ◽  
Dea Analysis ◽  
Low Efficiency ◽  
The Impact

My country’s current research on the influencing factors of total factor productivity has problems such as single evaluation method, low efficiency, and poor overall level in terms of evaluation methods and evaluation efficiency. Based on this, this study divides the financial structure into three traditional sections, banking, securities, and insurance, and uses the DEA model to study the temporal and spatial differences of the financial structure’s influence on the total factor productivity of the four major political and economic regions of China’s eastern, western, central, and northeastern China. First, establish a DEA model based on data mining algorithms, combine financial data comparisons over the years, to achieve a quantitative analysis of the financial structure’s impact on China’s total factor productivity, calculate financial efficiency, and then combine the DEA analysis data model with the grey correlation method. Analyze its internal influence rules, and design experiments for model verification analysis. The results show that the DEA analysis model can realize 8 iterations of data on the impact of financial structure on China’s total factor productivity, and its evaluation accuracy can reach more than 96.2%.

Turbine Blade Life Prediction Using Fluid-Thermal-Structural Interaction Modelling

2015 ◽  
Author(s):  
I. A. Ubulom ◽  
K. Shankar ◽  
A. J. Neely
Keyword(s):  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Experimental Testing ◽  
Fluid Structure Interaction ◽  
High Stress ◽  
Time History ◽  
Life Assessment ◽  
Fluid Structure ◽  
Operational Conditions ◽  
Structure Interaction

The stringent structural requirements posed on aircraft engines, especially the high pressure turbine blades, result from the diversity of the extreme operational conditions they are subjected to. The accurate life assessment of the blades under these conditions therefore demands accurate analytical tools and techniques, and also an elaborate understanding of the operational conditions. Given the drive to reduce cost related to experimental testing, numerical approaches are often adopted to aid in the initial design stages. With recent advancement in numerical modelling, the simultaneous integration of the various numerical codes of fluid flow and structural analysis (otherwise known as fluid-structure interaction) is projected to provide reliable input into fatigue life prediction programs. This study adopts the numerical method of fluid-structure interaction to investigate the fatigue properties of the Aachen turbine test case. A load-time history obtained for the high stress monitor position is superimposed on that from a quasi-static FE solution, and used as input into a fatigue estimation tool. The low cycle fatigue (LCF) is estimated using the Basquin-Coffin-Manson correlation with corrections for mean stress and multi-axial fatigue effects. An FFT analysis of the fluctuating aerodynamic loads show signals with significant high frequency content. There is noticeable increased energy signal at the rotor inlet as compared to stator inlet. The stator inlet signals, however, are characterized by multiple resonances of frequency with lower energy content. By avoiding the resonances, the fatigue analysis predicts a safe design with a safety factor level of 3 for the rotor.

Modeling of Contact/Impact Problems in Gear Systems Dynamics

1999 ◽  
Author(s):  
Leszek Demkowicz ◽  
Andrzej Bajer
Keyword(s):  
Model Problem ◽  
Body Motion ◽  
Systems Dynamics ◽  
Elastic Rod ◽  
Element Discretization ◽  
Elastic Wheel ◽  
One Step ◽  
Contact Impact ◽  
Impact Problems ◽  
Impact Problem

Abstract A discretization scheme for contact/impact problems related to the modeling of gears is proposed. The problem is first discretized in time and then a variational formulation for the resulted one step problem is developed. A Finite Element discretization completes the discretization process. The scheme is reinterpretation of the general Simo-Laursen-Chavla algorithm in the contest of rigid body motion superimposed with small elastic deformation; it conserves precisely linear momentum and total energy, and approximately the angular momentum. The discretization method is illustrated with two numerical examples: the standard 1D impact problem for an elastic rod, and a 2D model problem of an elastic wheel bouncing within a constraining box.

scholarly journals Spatially Tracking Wave Events in Partitioned Numerical Wave Model Outputs

2019 ◽  
Vol 36 (10) ◽  
pp. 1933-1944 ◽  
Author(s):  
Haoyu Jiang
Keyword(s):  
Grid Point ◽  
Wave Model ◽  
Ocean Waves ◽  
Model Verification ◽  
Analysis Model ◽  
Wave Parameters ◽  
Numerical Wave ◽  
Wave Models ◽  
Spectral Partitioning ◽  
The Impact

AbstractNumerical wave models can output partitioned wave parameters at each grid point using a spectral partitioning technique. Because these wave partitions are usually organized according to the magnitude of their wave energy without considering the coherence of wave parameters in space, it can be difficult to observe the spatial distributions of wave field features from these outputs. In this study, an approach for spatially tracking coherent wave events (which means a cluster of partitions originating from the same meteorological event) from partitioned numerical wave model outputs is presented to solve this problem. First, an efficient traverse algorithm applicable for different types of grids, termed breadth-first search, is employed to track wave events using the continuity of wave parameters. Second, to reduce the impact of the garden sprinkler effect on tracking, tracked wave events are merged if their boundary outlines and wave parameters on these boundaries are both in good agreement. Partitioned wave information from the Integrated Ocean Waves for Geophysical and other Applications dataset is used to test the performance of this spatial tracking approach. The test results indicate that this approach is able to capture the primary features of partitioned wave fields, demonstrating its potential for wave data analysis, model verification, and data assimilation.

A Homogenization Method for the Modal Analysis of a Nuclear Reactor With Fluid-Structure Interaction

2006 ◽  
Author(s):  
Jean-Franc¸ois Sigrist ◽  
Daniel Broc
Keyword(s):  
Modal Analysis ◽  
Nuclear Reactor ◽  
Mass Operator ◽  
Fluid Structure Interaction ◽  
Homogenization Method ◽  
Theoretical Point ◽  
Element Discretization ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Internal Structures

The present paper exposes a homogenization method developed in order to perform the modal analysis of a nuclear reactor with fluid-structure interaction effects. The homogenization approach is used in order to take into account the presence of internal structures within the pressure vessel. A homogenization method is proposed in order to perform a numerical calculation of the frequencies and modal masses for the eigenmodes of the coupled fluid-structure problem. The technique allows the use of a simplified fluid-structure model that takes into account the presence of internal structures: the theory bases are first recalled, leading to a new formulation of the fluid-structure coupled problem. The finite element discretization of the coupled formulation leads to the modification of the classical fluid-structure interaction operators. The consistency of the formulation is established from a theoretical point of view by evaluating the total mass of the coupled system with the fluid and structure mass operator, and the modified added mass operator. The method is tested and validated on a 2D case (two concentric cylinders with periodical rigid inclusions within the annular space) and applied on the industrial case. A complete modal analysis (calculation of frequencies and modal masses) is performed on a simplified geometry of a nuclear reactor with and without internal structures. Numerical results are then compared and discussed, and the influence of the internal structures on the fluid-structure coupled phenomenon is highlighted.

Production Performance Analysis for Multi-Branched Horizontal Wells in Composite Coal Bed Methane Reservoir Considering Stress Sensitivity

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Ruizhong Jiang ◽  
Xiuwei Liu ◽  
Yongzheng Cui ◽  
Xing Wang ◽  
Yue Gao ◽  
...  
Keyword(s):  
Superposition Principle ◽  
Horizontal Wells ◽  
Stress Sensitivity ◽  
Field Application ◽  
Model Verification ◽  
Production Performance ◽  
Coal Bed ◽  
Coal Bed Methane ◽  
Element Discretization ◽  
Type Curves

Abstract Coal bed methane (CBM) significantly contributes to unconventional energy resources. With the development of the drilling technology, multi-branched horizontal wells (MBHWs) have been put into the exploitation of CBM. In this paper, a semi-analytical mathematical model is introduced to study the production characteristics of MBHWs in the composite CBM reservoir. Stress sensitivity, composite reservoir, and complex seepage mechanisms (desorption, diffusion, and Darcy flow) are taken into consideration. Through Pedrosa transformation, Perturbation transformation, Laplace transformation, Finite cosine transformation, element discretization, superposition principle, and Stehfest numerical inversion, pseudo-pressure dynamic curves and production decline curves are plotted and 13 flow regimes are divided. Then, the sensitivity analysis of related parameters is conducted to study the influences of these parameters based on these two type curves. Model verification and field application are introduced which shows that the model is reliable. The model proposed in this paper and relevant results analysis can provide some significant guidance for a better understanding of the production behavior of MBHWs in the composite CBM reservoir.

Analysis of Composite Shrinkage Stresses on 3D Premolar Models with Different Cavity Design Using Finite Element Method

2013 ◽  
Vol 586 ◽  
pp. 202-205 ◽  
Author(s):  
Milos Milosevic ◽  
Nenad Mitrovic ◽  
Vesna Miletić ◽  
Uroš Tatic ◽  
Andrea Ezdenci
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Models ◽  
Experimental Testing ◽  
Fem Analysis ◽  
Local Stress ◽  
Model Verification ◽  
Polymerization Shrinkage ◽  
Displacement Analysis ◽  
Element Method

Local polymerization stress occurs due to polymerization shrinkage of resin based composites adhesively bonded to tooth tissues. Shrinkage causes local displacements of cavity walls, with possible occurrence of micro-cracks in the enamel, dentin and/or material itself. In order to design a cavity for experimental testing of polymerization shrinkage of dental composites using 3D optical analysis, in this paper finite element method (FEM) was used to analyze numerical models with different cavity radiuses. 3D optical strain and displacement analysis of composite materials and cavity walls is limited by equipment sensitivity i.e. 0.01% for strain and 1 micron for displacement. This paper presents the development of 3D computer premolar models with varying cavity radiuses, and local stress, strain and displacement analysis using FEM. Model verification was performed by comparing obtained results with data from the scientific literature. Using the FEM analysis of local strains, displacements and stresses exerted on cavity walls, it was concluded that the model with 1 mm radius was optimal for experimental optical 3D displacement analysis.

scholarly journals On the nonlinear dynamics of a rotor in autorotation: a combined experimental and numerical approach

2015 ◽  
Vol 373 (2051) ◽  
pp. 20140411 ◽  
Author(s):  
D. Rezgui ◽  
M. H. Lowenberg
Keyword(s):  
Nonlinear Dynamics ◽  
Experimental Testing ◽  
Simple Procedure ◽  
Numerical Approach ◽  
Numerical Continuation ◽  
Engineering Systems ◽  
Systematic Assessment ◽  
Instability Problem ◽  
Physical Testing ◽  
Periodic Behaviour

This article presents a systematic assessment of the use of numerical continuation and bifurcation techniques in investigating the nonlinear periodic behaviour of a teetering rotor operating in forward autorotation. The aim is to illustrate the potential of these tools in revealing complex blade dynamics, when used in combination (not necessarily at the same time) with physical testing. We show a simple procedure to promote understanding of an existing but not fully understood engineering instability problem, when uncertainties in the numerical modelling and constraints in the experimental testing are present. It is proposed that continuation and bifurcation methods can play a significant role in developing numerical and experimental techniques for studying the nonlinear dynamics not only for rotating blades but also for other engineering systems with uncertainties and constraints.

Fluid-Structure Interaction Effects Modeling for the Modal Analysis of a Nuclear Pressure Vessel

2006 ◽  
Vol 129 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Jean-François Sigrist ◽  
Daniel Broc ◽  
Christian Lainé
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Pressure Vessel ◽  
Nuclear Reactor ◽  
Fluid Structure Interaction ◽  
Added Mass ◽  
Interaction Effects ◽  
Element Discretization ◽  
Fluid Structure ◽  
Structure Interaction

The present paper deals with the modal analysis of a nuclear reactor with fluid-structure interaction effects. The proposed study aims at describing various fluid-structure interaction effects using several numerical approaches. The modeling lies on a classical finite element discretization of the coupled fluid-structure equation, enabling the description of added mass and added stiffness effects. A specific procedure is developed in order to model the presence of internal structures within the nuclear reactor, based on periodical homogenization techniques. The numerical model of the nuclear pressure vessel is developed in a finite element code in which the homogenization method is implemented. The proposed methodology enables a convenient analysis from the engineering point of view and gives an example of the fluid-structure interaction effects, which are expected on an industrial structure. The modal analysis of the nuclear pressure vessel is then performed and highlights of the relative importance of FSI effects for the industrial case are evaluated: the analysis shows that added mass effects and confinement effects are of paramount importance in comparison to added stiffness effects.

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