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Persistent URL http://purl.org/net/epubs/work/41463499
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Record Id 41463499
Title Uncertainty Quantification of Conjugate Heat Transfer in Stratified Fluid Flow: Application of non-intrusive polynomial chaos
Abstract Knowledge of a system’s response to unknown operating conditions can be of key importance in engineering design. A standard engineering approach might involve performing a small handful of calculations to assess the influence of operating conditions on quantities of interest. However, this simple approach may provide an incomplete picture, potentially leading to poor design decisions. A brute-force approach (performing a large number of simulations, over a range of operating conditions) can provide a more complete mapping between inputs and outputs, but at a significant computational cost. In this work we apply advanced uncertainty quantification techniques which allow us to maximise the knowledge extracted from the modelled system and, crucially, its response to uncertain input parameters. This is done without changing existing simulation codes. In the report, we show that we can perform such a study in a more efficient manner than the brute-force approach – at least 1-2 orders of magnitude less computational cost, with no loss in accuracy. We demonstrate the use of these tools by assessing the propagation of thermal transients within a u-shaped bend. A hot-shock is introduced at the inlet, and allowed to propagate through the domain. This test-case is relevant to nuclear applications, where hot-cold cycles can lead to thermal fatigue and material failure. The influence shock-magnitude on wall temperatures (or wall stresses) is assessed. Rapid low-fidelity RANS (Reynolds-averaged Navier–Stokes) simulations, as typically used in industry, form the basis of the model. The analysis we present shows a bi-modal response, in which extreme values of temperature within the pipe walls are more likely to occur than the mean value (despite a uniform distribution on the inlet shock-magnitude). Standard engineering practice may miss this as mean values are often focussed upon. The study reveals that the input-output-mapping for this flow is complex and requires novel approaches to efficiently determine the statistics. In addition to the wall-temperatures, we also asses the thermally-induced stresses within the solid domain. We achieve this by coupling the Computational Fluid Dynamics (CFD) code with a Finite Element Method (FEM) code for stress analysis. A one-way coupling is performed, as solid displacements have an insignificant influence on the fluid-flow. This preliminary work is important as it will allow us to infer the likelihood of thermal fatigue (when coupled with an empirical fatigue model). For the test-case under consideration, stresses close to the yield-stress are observed, and hence thermal fatigue would be likely within only a few cycles.
Organisation STFC , SCI-COMP , HC
Funding Information BEIS, Innovation Return on Research
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Language English (EN)
Type Details URI(s) Local file(s) Year
Report IBM, 2019. report-1.pdf 2019