Coupling algorithms for fluid structure interaction at low density ratios- Accuracy and stability analysis of weak coupling algorithms in partioned codes

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dc.contributor.authorOttosson, Martin
dc.contributor.departmentChalmers tekniska högskola / Institutionen för mekanik och maritima vetenskapersv
dc.contributor.departmentChalmers University of Technology / Department of Mechanics and Maritime Sciencesen
dc.date.accessioned2019-07-03T14:58:27Z
dc.date.available2019-07-03T14:58:27Z
dc.date.issued2018
dc.description.abstractIn recent years the interest of numerical predictions of fluid-structure interaction has grown in industrial applications as well as in the research of the phenomenon due to the increase in computational power. Numerical predictions of fluid-structure interaction typically suffers from instability when the solid-to-fluid density ratio becomes small. The instability issues are most severe when weak coupling, without coupling iterations within each time step, methods are used. Further, the weak coupling introduces the so-called artificial added mass effect, that introduces an error in the coupling. At Fraunhofer-Chalmers Centre a state-of-the-art multiphase solver, IBOFlow, and a structural solver, LaStFEM, are developed. IBOFlow handles moving boundaries using the mirroring immersed boundary method with adaptive grid refinements. The incompressible Navier-Stokes equations together with the boundary conditions at the structural interface are solved on a Eulerian grid using the finite volume method. LaStFEM solves the structural equations together with the forces acting on the structural interface on a Lagrangian grid using the finite element method. In previous work, a strong coupling, with coupling iterations within each time step, and a simple weak coupling procedure has been implemented and validated. In this thesis different weak coupling procedures are implemented, compared and analyzed in the existing frame work. The accuracy and stability of the weak coupling algorithms are investigated and compared to the existing strong coupling procedure. The investigation is done by the usage of three benchmarking cases: A rigid sphere attached to an undamped spring in Stokes flow, a rigid cylinder attached to a damped spring in a laminar flow and an elastic beam attached to a rigid cylinder in a laminar flow. The temporal and spatial accuracy are both found to be of second-order. The lowest solid-to-fluid density ratio where a stable solution was achived using a weak coupling algorithm is well below one and much smaller than what has been found in the literature.
dc.identifier.urihttps://hdl.handle.net/20.500.12380/256396
dc.language.isoeng
dc.relation.ispartofseriesExamensarbete - Institutionen för mekanik och maritima vetenskaper : 2018:38
dc.setspec.uppsokTechnology
dc.subjectMaterialvetenskap
dc.subjectHållbar utveckling
dc.subjectStrömningsmekanik och akustik
dc.subjectMaterials Science
dc.subjectSustainable Development
dc.subjectFluid Mechanics and Acoustics
dc.titleCoupling algorithms for fluid structure interaction at low density ratios- Accuracy and stability analysis of weak coupling algorithms in partioned codes
dc.type.degreeExamensarbete för masterexamensv
dc.type.degreeMaster Thesisen
dc.type.uppsokH
local.programmeApplied mechanics (MPAME), MSc
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