A fast strong coupling algorithm for the partitioned fluid–structure interaction simulation of BMHVs

The numerical simulation of Bileaflet Mechanical Heart Valves (BMHVs) has gained strong interest in the last years, as a design and optimisation tool. In this paper, a strong coupling algorithm for the partitioned fluidstructure interaction simulation of a BMHV is presented. The convergence of the coupling iterations between the flow solver and the leaflet motion solver is accelerated by using the Jacobian with the derivatives of the pressure and viscous moments acting on the leaflets with respect to the leaflet accelerations. This Jacobian is numerically calculated from the coupling iterations. An error analysis is done to derive a criterion for the selection of useable coupling iterations. The algorithm is successfully tested for two 3D cases of a BMHV and a comparison is made with existing coupling schemes. It is observed that the developed coupling scheme outperforms these existing schemes in needed coupling iterations per time step and CPU time

Application of a strong FSI coupling scheme for the numerical simulation of bileaflet mechanical heart valve dynamics: study of wall shear stress on the valve leaflets

One of the major challenges in the design of Bileaflet Mechanical Heart Valves (BMHVs) is reduction of the blood damage generated by non-physiological blood flow. Numerical simulations provide relevant insights into the (fluid) dynamics of the BMHV and are used for design optimisation. In this paper, a strong coupling algorithm for the partitioned Fluid-Structure Interaction (FSI) simulation of a BMHV is presented. The convergence of the coupling iterations between the flow solver and the leaflet motion solver is accelerated by using a numerically calculated Jacobian with the derivatives of the pressure and viscous moments acting on the leaflets with respect to the leaflet accelerations. The developed algorithm is used to simulate the dynamics of a 3D BMHV in three different geometries, allowing an analysis of the solution process. Moreover, the leaflet kinematics and the general flow field are discussed, with special focus on the shear stresses on the valve leaflets

FSI simulation of asymmetric mitral valve dynamics during diastolic filling

In this article, we present a fluid-structure interaction algorithm accounting for the mutual interaction between two rigid bodies. The algorithm was used to perform a numerical simulation of mitral valve (MV) dynamics during diastolic filling. In numerical simulations of intraventricular flow and MV motion, the asymmetry of the leaflets is often neglected. In this study the MV was rendered as two rigid, asymmetric leaflets. The 2D simulations incorporated the dynamic interaction of blood flow and leaflet motion and an imposed subject-specific, transient left ventricular wall movement obtained from ultrasound recordings. By including the full Jacobian matrix in the algorithm, the speed of the simulation was enhanced by more than 20% compared to using a diagonal Jacobian matrix. Furthermore, our results indicate that important features of the flow field may not be predicted by the use of symmetric leaflets or in the absence of an adequate model for the left atrium

Velocity profiles in the human ductus venosus: a numerical fluid structure interaction study

The veins distributing oxygenated blood from the placenta to the fetal body have been given much attention in clinical Doppler velocimetry studies, in particular the ductus venosus. The ductus venosus is embedded in the left liver lobe and connects the intra-abdominal portion of the umbilical vein (IUV) directly to the inferior vena cava, such that oxygenated blood can bypass the liver and flow directly to the fetal heart. In the current work, we have developed a mathematical model to assist the clinical assessment of volumetric flow rate at the inlet of the ductus venosus. With a robust estimate of the velocity profile shape coefficient (VC), the volumetric flow rate may be estimated as the product of the time-averaged cross-sectional area, the time-averaged cross-sectional maximum velocity and the VC. The time average quantities may be obtained from Doppler ultrasound measurements, whereas the VC may be estimated from numerical simulations. The mathematical model employs a 3D fluid structure interaction model of the bifurcation formed by the IUV, the ductus venosus and the left portal vein. Furthermore, the amniotic portion of the umbilical vein, the right liver lobe and the inferior vena cava were incorporated as lumped model boundary conditions for the fluid structure interaction model. A hyperelastic material is used to model the structural response of the vessel walls, based on recently available experimental data for the human IUV and ductus venous. A parametric study was constructed to investigate the VC at the ductus venosus inlet, based on a reference case for a human fetus at 36 weeks of gestation. The VC was found to be (Mean SD of parametric case study), which confirms previous studies in the literature on the VC at the ductus venosus inlet. Additionally, CFD simulations with rigid walls were performed on a subsection of the parametric case study, and only minor changes in the predicted VCs were observed compared to the FSI cases. In conclusion, the presented mathematical model is a promising tool for the assessment of ductus venosus Doppler velocimetry

Numerical Simulation of Biological Structures

IASS-IACM 2008 Session: Numerical Simulation of Biological Structures -- Session Organizer: Wilkins AQUINO (Cornell University) -- Keynote Lecture: "Computational modeling of glucose distribution in hollow fiber membrane bioreactors" by G.U. UNIKRISHNAN, V.U. UNIKRISHNAN, J.N. REDDY (Texas A and M University) -- "Characterization of viscoelastic properties of cylindrical vessels using the velocity response produced by an impulsive force" by Daniel E. ROSARIO, Wilkins AQUINO (Cornell University) -- "Solid versus membrane finite elements in analysis of the mitral valve: A case study" by Victorien PROT , Bjorn SKALLERUD (Norwegian University of Science and Technology) -- "An inverse problem approach for elasticity imaging through vibroacoustics" by Miguel AGUILO, Wilkins AQUINO (Cornell University) -- "Proper orthogonal decomposition model reduction for inverse problems in acoustic-structure interaction" by John C. BRIGHAM, Wilkins AQUINO (Cornell University) -- "Shell analysis of elliptical guard cells in higher plants: A review" by J. Robert COOKE , Richard RAND (Cornell University), Herbert MANG (TU Vienna), Josse DeBAERDEMAEKER (Katholieke Universiteit Leuven), Jae Young LEE (Chonbuk National University) -- "In vivo ultrasound bone property determination through inverse finite element modeling" by Mija HUBLER , Wilkins AQUINO, Christopher EARLS (Cornell University) -- "Finite element analyses of palm leaf petiole-sheath junctions in simple bending and twisting and in dynamic (oscillatory) flexure" by Karl NIKLAS , J. Robert COOKE (Cornell University), Jae Young LEE (Chonbuk National University) -- "Modeling pipette aspiration of biological membranes" by Philip BUSKOHL (Cornell University) -- "A new model for nucleation in two-phase lipid bilayer membrane vesicles" by Sanjay DHARMAVARAM , Timothy HEALEY (Cornell University

Fracture in Natural and Engineered Systems

IASS-IACM 2008 Session: Fracture in Natural and Engineered Systems -- Session Organizers: Robert HABER (UIUC), Anthony INGRAFFEA (Cornell Univ.) -- Keynote Lecture: "Assessment of stiffened shell structures using advanced fracture and damage mechanics methods" by Karl-Heinz SCHWALBE , Wolfgang BROCKS, Alfred CORNEC, Wernfried Schonfeld, Ingo SCHEIDER, Uwe ZERBST (GKSS Research Centre) -- "Residual strength characterization of integrally-stiffened structures utilizing novel manufacturing technologies" by B. R. SESHADRI, S. W. SMITH , W. M. JOHNSTON, JR. (NASA Langley Research Center) -- "Towards modeling of fragmentation and dynamic delamination interactions in CFRP composites" by Jean-Mathieu GUIMARD , Oliver ALLIX (ENS Cachan), Nicolas PECHNIK (AIRBUS France), Pascal THEVENET (EADS France) -- "A damage-based cohesive model in an adaptive spacetime discontinuous Galerkin method" by Reza ABEDI, Robert B. HABER (University of Illinois at Urbana-Champaign) -- "A unified potential-based cohesive model of mixed-mode fracture" by Glaucio H. PAULINO , Kyoungsoo PARK, Jeffrey ROESLER (The University of Illinois at Urbana-Champaign) -- "Surface and embedded cracks in offshore pipelines subjected to plastic strains" by Espen BERG , Bjorn SKALLERUD, Kjell HOLTHE (Norwegian University of Science and Technology) -- "Automated finite element based predictions of simultaneous crack growth and delamination growth in multi-layers in advanced metallic hybrid stiffened panels using the Alcoa ASPAN-FP tool" by Henry SKLYUT , Michael KULAK, Marcus HEINIMANN, Mark JAMES (Alcoa Technical Center), Olexander V. GONDLIAKH, Roman PASHINSKIJ (KPI, Kiev, Ukraine) -- "Crack trajectory prediction in thin shells using finite element analysis" by Jake D. HOCHHALTER , Ashley D. SPEAR, Anthony R. INGRAFFEA (Cornell University) -- "Analysis of localized failure in metal beams and plates" by Jaka DUJC, Bostjan BRANK (University of Ljubljana), Adnan IBRAHIMBEGOVIC (ENS Cachan