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Uncertainty Quantification in Flow and Flow Induced Structural Response

Electronic Theses of Indian Institute of Science

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Title Uncertainty Quantification in Flow and Flow Induced Structural Response
 
Creator Suryawanshi, Anup Arvind
 
Subject Flexible Structures
Structural Uncertainty Quantification
Spatio-temporal Random Process
Computational Mechanics
Wind Speed Prediction
Limit Cycle Oscillations (LCOs)
Spatio-temporal Covariance
Flow and Flow Induced Structural Response
Structural Stability
Polynomial Chaos
Hybrid Sampling Technique
Aeroelasticity
Aeroelastic Stability
Civil Engineering
 
Description Response of flexible structures — such as cable-supported bridges and aircraft wings — is associated with a number of uncertainties in structural and flow parameters. This thesis is aimed at efficient uncertainty quantification in a few such flow and flow-induced structural response problems.
First, the uncertainty quantification in the lift force exerted on a submerged body in a potential flow is considered. To this end, a new method — termed here as semi-intrusive stochastic perturbation (SISP) — is proposed. A sensitivity analysis is also performed, where for the global sensitivity analysis (GSA) the Sobol’ indices are used. The polynomial chaos expansion (PCE) is used for estimating these indices. Next, two stability problems —divergence and flutter — in the aeroelasticity are studied in the context of reliability based design optimization (RBDO). Two modifications are proposed to an existing PCE-based metamodel to reduce the computational cost, where the chaos coefficients are estimated using Gauss quadrature to gain computational speed and GSA is used to create nonuniform grid to reduce the cost even further. The proposed method is applied on a rectangular unswept cantilever wing model. Next, reliability computation in limit cycle oscillations (LCOs) is considered. While the metamodel performs poorly in this case due to bimodality in the distribution, a new simulation-based scheme proposed to this end. Accordingly, first a reduced-order model (ROM) is used to identify the critical region in the random parameter space. Then the full-scale expensive model is run only over a this critical region. This is applied to the rectangular unswept cantilever wing with cubic and fifth order stiffness terms in its equation of motion.
Next, the wind speed is modeled as a spatio-temporal process, and accordingly new representations of spatio-temporal random processes are proposed based on tensor decompositions of the covariance kernel. These are applied to three problems: a heat equation, a vibration, and a readily available covariance model for wind speed. Finally, to assimilate available field measurement data on wind speed and to predict based on this assimilation, a new framework based on the tensor decompositions is proposed. The framework is successfully applied to a set of measured data on wind speed in Ireland, where the prediction based on simulation is found to be consistent with the observed data.
 
Contributor Ghosh, Debraj
 
Date 2018-07-23T07:32:08Z
2018-07-23T07:32:08Z
2018-07-23
2015
 
Type Thesis
 
Identifier http://etd.iisc.ernet.in/2005/3875
http://etd.iisc.ernet.in/abstracts/4747/G26886-Abs.pdf
 
Language en_US
 
Relation G26886