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A 3D full-friction contact model for fluid-structure interaction problems
KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST). (Computational Technology Laboratory)ORCID iD: 0000-0002-7342-1987
KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST). (Computational Technology Laboratory)
KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST). (Computational Technology Laboratory)ORCID iD: 0000-0002-1695-8809
KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST). (Computational Technology Laboratory)ORCID iD: 0000-0003-4256-0463
(English)Manuscript (preprint) (Other academic)
Keywords [en]
Contact model, fluid-structure interaction, finite element method, Arbitrary Lagrangian-Eulerian method, parallel algorithm
National Category
Computational Mathematics
Research subject
Applied and Computational Mathematics
Identifiers
URN: urn:nbn:se:kth:diva-215166OAI: oai:DiVA.org:kth-215166DiVA, id: diva2:1146746
Note

QC 20171006

Available from: 2017-10-03 Created: 2017-10-03 Last updated: 2018-05-08Bibliographically approved
In thesis
1. Patient-Specific Finite Element Modeling of the Blood Flow in the Left Ventricle of a Human Heart
Open this publication in new window or tab >>Patient-Specific Finite Element Modeling of the Blood Flow in the Left Ventricle of a Human Heart
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Heart disease is the leading cause of death in the world. Therefore, numerous studies are undertaken to identify indicators which can be applied to discover cardiac dysfunctions at an early age. Among others, the fluid dynamics of the blood flow (hemodymanics) is considered to contain relevant information related to abnormal performance of the heart.This thesis presents a robust framework for numerical simulation of the fluid dynamics of the blood flow in the left ventricle of a human heart and the fluid-structure interaction of the blood and the aortic leaflets.We first describe a patient-specific model for simulating the intraventricular blood flow. The motion of the endocardial wall is extracted from data acquired with medical imaging and we use the incompressible Navier-Stokes equations to model the hemodynamics within the chamber. We set boundary conditions to model the opening and closing of the mitral and aortic valves respectively, and we apply a stabilized Arbitrary Lagrangian-Eulerian (ALE) space-time finite element method to simulate the blood flow. Even though it is difficult to collect in-vivo data for validation, the available data and results from other simulation models indicate that our approach possesses the potential and capability to provide relevant information about the intraventricular blood flow.To further demonstrate the robustness and clinical feasibility of our model, a semi-automatic pathway from 4D cardiac ultrasound imaging to patient-specific simulation of the blood flow in the left ventricle is developed. The outcome is promising and further simulations and analysis of large data sets are planned.In order to enhance our solver by introducing additional features, the fluid solver is extended by embedding different geometrical prototypes of both a native and a mechanical aortic valve in the outflow area of the left ventricle.Both, the contact as well as the fluid-structure interaction, are modeled as a unified continuum problem using conservation laws for mass and momentum. To use this ansatz for simulating the valvular dynamics is unique and has the expedient properties that the whole problem can be described with partial different equations and the same numerical methods for discretization are applicable.All algorithms are implemented in the high performance computing branch of Unicorn, which is part of the open source software framework FEniCS-HPC. The strong advantage of implementing the solvers in an open source software is the accessibility and reproducibility of the results which enhance the prospects of developing a method with clinical relevance.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 51
Series
TRITA-CSC-A, ISSN 1653-5723 ; 2017:21
Keywords
Finite element method, Arbitrary Lagrangian-Eulerian method, Fluid-Structure interaction, Contact model, parallel algorithm, blood flow, left ventricle, aortic valves, patient-specific heart model
National Category
Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-215277 (URN)978-91-7729-566-2 (ISBN)
Public defence
2017-10-27, Fantum, F-huset, plan 5, KTH Campus, Lindstedtsvägen 24, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilEU, European Research Council, 202984
Note

QC 20171006

Available from: 2017-10-06 Created: 2017-10-05 Last updated: 2017-10-09Bibliographically approved
2. Adaptive Finite Element Methods for Fluid Structure Interaction Problems with Applications to Human Phonation
Open this publication in new window or tab >>Adaptive Finite Element Methods for Fluid Structure Interaction Problems with Applications to Human Phonation
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This work presents a unified framework for numerical solution of Fluid Structure Interaction (FSI) and acoustics problems with focus on human phonation. The Finite Element Method is employed for numerical investigation of partial differential equations that model conservation of momentum and mass. Since the resulting system of equations is very large, an efficient open source high performance implementation is constructed and provided. In order to gain accuracy for the numerical solutions, an adaptive mesh refinement strategy is employed which reduces the computational cost in comparison to a uniform refinement. Adaptive refinement of the mesh relies on computable error indicators which appear as a combination of a computable residual and the solution of a so-called dual problem acting as weights on computed residuals. The first main achievement of this thesis is to apply this strategy to numerical simulations of a benchmark problem for FSI. This FSI model is further extended for contact handling and applied to a realistic vocal folds geometry where the glottic wave formation was captured in the numerical simulations. This is the second achievement in the presented work. The FSI model is further coupled to an acoustics model through an acoustic analogy, for vocal folds with flow induced oscillations for a domain constructed to create the vowel /i/. The comparisons of the obtained pressure signal at specified points with respect to results from literature for the same vowel is reported, which is the final main result presented.

Abstract [sv]

Detta arbete presenterar en enhetlig ram för numerisk lösning av fluid-strukturinteraktion (FSI) och akustikproblem med fokus på det mänskligatalet. En finita elementmetod används för numerisk lösning av de partiella differentialekvationer som beskriver konserveringslagar för moment och massa.Eftersom det resulterande systemet av ekvationer är mycket stort, konstruerasen öppen källkod med hög prestanda. För att få hög noggrannhet i de numeriska lösningarna används en adaptiv nätförfiningsstrategi vilken minskar beräkningskostnaden jämfört med en uniform förfining.Adaptiv förfining av nätet bygger på beräknade felindikatorer som bygger på en kombination av en beräkningsbar residual och lösningen av ett såkallat dualt problem. Den första huvudresultatet av denna avhandling är attutveckla en och validera denna strategi för en FSI-modell i ett benchmarkproblem.Denna FSI-modell utvidgas vidare för att hantera kontaktmekanik, ochanvänds sedan för en realistisk modell av stämbandsstrukturerna där denglottiska vågformationen fångas i de numeriska simuleringarna. Detta är detandra huvudresultatet i det presenterade arbetet.FSI-modellen kopplas också till en akustikmodell genom en akustisk analogi,för modell konstruerad för att skapa vokalen / i /. Den erhållna trycksignaleni ett antal punkter jämförs med resultat från litteraturen, vilket är det slutligahuvudresultatet som presenteras.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2018. p. 48
Series
TRITA-EECS-AVL ; 2018:38
Keywords
Fluid Structure Interaction, Finite Element Method, Contact Modeling, Acoustic Coupling, High Performance Computing
National Category
Computational Mathematics
Research subject
Applied and Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-227252 (URN)978-91-7729-764-2 (ISBN)
Public defence
2018-05-23, F3, Sing-Sing, floor 2, KTH Kungliga Tekniska högskolan, Lindstedtsvägen 26, Stockholm, Stockholm, 10:30 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 308874Swedish Foundation for Strategic Research Swedish Research CouncilEU, European Research Council
Note

QC 20180509

Available from: 2018-05-09 Created: 2018-05-08 Last updated: 2018-05-09Bibliographically approved

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Spühler, Jeannette HiromiJansson, JohanHoffman, Johan

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