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On the swirl-switching in developing bent pipe flow with direct numerical simulation
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Om swirl-switching i ett böjt rörflöde med direkt numerisk simulering (Swedish)
Abstract [en]

This work deals with the computational setup, simulation and analysis of turbulent flow through developing bent pipes. Specifically the effect of swirl-switching for the Dean vortices is analysed. A synthetic turbulent inflow condition is implemented and validated. Simulations are carried out with full resolution of the turbulent spatial and temporal scales.

The flow is analysed by means of a two- and three-dimensional proper orthogonal ecomposition method (POD) to identify energetically dominant, independent coherent structures in the flow. For the first time, results show the spatially travelling character of the swirl-switching phenomenon. Moreover, additional results are found to agree with existing experimental research and are related with the newly found ones. Thereby, weaknesses of the previous approaches are identified. The current results may provide a route towards low-order modelling of the flow in bent pipes.

Abstract [sv]

Detta arbete behandlar beräkningssimulering och analys av turbulent flöde genom böjda rör. Specifikt analyseras effekten av swirl-switching för Dean vortices, därför implementeras och valideras ett syntetisk turbulent inflödes randvillkor. Simuleringar genomförs i full upplösning av de turbulenta skalor.

Flödesfältet analyseras med hjälp av en proper orthogonal decomposition metod (POD) för att identifiera energetiskt dominanta, oberoende koherenta strukturer i flödet. För första gången visar resultatet att swirl-switching fenomenet baseras på en rörande våg. Vidare överrensstämmer ytterligare resultat med befintlig experimentell forskning samtidigt som de passar in med de nyfunna resultaten. Därigenom är svagheterna i den tidigare experimentella metoden identifierade. De aktuella resultaten kan ge en väg mot låg ordning modellering av flödet i böjda rör.

Place, publisher, year, edition, pages
TRITA-MAT-E, 2016:55
National Category
Computational Mathematics
URN: urn:nbn:se:kth:diva-192210OAI: diva2:963050
Subject / course
Scientific Computing
Educational program
Master of Science - Applied and Computational Mathematics
Available from: 2016-09-07 Created: 2016-09-07 Last updated: 2016-09-07Bibliographically approved

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