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Saad’s paper is accepted for publication in J Comput Phys

April 27, 2021

Saad’s paper, The smooth forcing extension method: A high-order technique for solving elliptic equations on complex domains, has been accepted to appear in Journal of Computational Physics. (A preprint is available on the arXiv.) This paper introduces a new high-order accurate approach, the smooth forcing extension method, to elliptic equations in complex geometries using Fourier continuation methods.

The smooth forcing extension method is similar to the immersed boundary smooth extension (IBSE) method introduced by Guy, Stein, Thomases, and co-workers, but it relies on extending the forcing term instead of the solution field from the “physical” to the “non-physical” domain. One consequence of this difference is that the smooth forcing extension method can yield a better conditioned system of equations than the IBSE formulation, which can yield improved accuracy at higher resolutions.

Amin’s paper is accepted for publication in J Comput Phys

April 12, 2021

Amin’s paper, A sharp interface Lagrangian-Eulerian method for rigid-body fluid-structure interaction, has been accepted to appear in Journal of Computational Physics. (A preprint is available on the arXiv.) This paper introduces a new sharp interface method to simulate fluid-structure interaction (FSI) involving rigid bodies immersed in viscous incompressible fluids by substantially extending Amin’s earlier work on immersed interface methods for discrete surfaces.

We refer to the numerical approach developed in this paper as an immersed Lagrangian-Eulerian (ILE) method. This ILE method integrates aspects of partitioned and immersed FSI formulations: it solves separate momentum equations for the fluid and solid subdomains, as in a partitioned formulation, while also using non-conforming discretizations of the dynamic fluid and structure regions, as in an immersed formulation.

An important aspect of the methodology is that, at least for all of the tests considered so far, it does not appear to suffer from so-called added mass effect instabilities. Indeed, tests suggest that it is capable of treating models with extremely small, nearly equal, equal, and large solid-fluid density ratios. The question of whether the ILE method does or does not suffer from the added mass effect awaits future analytical studies.

We are looking forward to future extensions and applications of this exciting new approach to FSI.

Congratulations, Amin!

Jianhua’s paper is accepted for publication in Journal of Computational Physics

August 27, 2020

Jianhua’s paper with Amin, An immersed interface-lattice Boltzmann method for fluid-structure interaction, has been accepted to appear in Journal of Computational Physics. (A preprint is available on the arXiv.) This paper develops what is, so far as we know, the first extension of the immersed interface method to lattice Boltzmann method-based descriptions of fluid flows.

Congratulations, Jianhua!

Ben’s paper is accepted for publication in Computer Methods in Applied Mechanics and Engineering

March 2, 2020

Ben’s paper, Stabilization Approaches for the Hyperelastic Immersed Boundary Method for Problems of Large-Deformation Incompressible Elasticity, has been accepted to appear in Computer Methods in Applied Mechanics and Engineering. (A preprint is available on the arXiv.) This paper proposes a simple stabilization that resembles approaches from nearly incompressible solid mechanics to improve the volume conservation of the immersed finite element method, as demonstrated by its performance in widely used benchmark problems of incompressible hyperelasticity adapted from the solid mechanics literature, along with fully dynamic FSI applications, including a large-scale model of esophageal transport.

Congratulations, Ben!

Charles’ paper is accepted for publication in Journal of Computational Physics

December 22, 2019

Charles’ paper, A Sharp Interface Method for an Immersed Viscoelastic Solid, has been accepted to appear in Journal of Computational Physics. (A preprint is available on the arXiv.) This paper develops an extension of the hyperelastic immersed boundary method that sharply resolves pressure discontinuities at fluid-structure interfaces by modifying the definition of the elastic stress tensor associated with the hyperelastic material response. Unlike most other sharp-interface immersed boundary methods, however, this approach allows us to use standard discretization methods that are “oblivious” to the presence of the pressure discontinuity. Numerical tests show the impact of the method on the accuracy of the overall scheme, and an approach is developed that allows us to compute the splitting efficiently.

Mike’s paper is accepted for publication in Annals of Biomedical Engineering

December 14, 2019

Mike’s paper, Fluid-Structure Interaction Models of Bioprosthetic Heart Valve Dynamics in an Experimental Pulse Duplicator, has been accepted to appear in Annals of Biomedical Engineering. (A preprint is available on engrXiv.) This paper uses IBAMR’s version of the immersed finite element method to simulate the dynamics of bioprosthetic heart valves (BHVs) in the aortic test section of experimental pulse duplicator systems. An initial experimental validation of the models is demonstrated through comparisons to data on pressures, flow rates, and leaflet kinematics. The paper also contrasts the flow patterns and leaflet strains and stresses generated by porcine tissue and bovine pericardial BHVs, and demonstrates the ability of the model to capture the large scale flow features.

Congratulations, Mike!

Amin’s paper is accepted for publication in Journal of Computational Physics

July 23, 2019

Amin’s paper, An immersed interface method for discrete surfaces, has been accepted to appear in the Journal of Computational Physics. (A preprint is available on the arXiv.) This paper develops an extension of the immersed interface method (IIM) that is specialized to discrete surface representations, such as triangulated surfaces. It also establishes through extensive numerical examples that IIMs that use only the lowest-order jump conditions (for the pressure and viscous shear stress) at immersed interfaces are able to yield global second-order convergence rates.

Congratulations, Amin!

Mike’s paper is on the engrXiv

February 15, 2019

Mike’s paper, Fluid-structure interaction models of bioprosthetic heart valves: Initial in vitro experimental validation, is now available on the engrXiv. This paper uses the hyperelastic immersed boundary method to simulate the dynamics of bioprosthetic heart valves (BHVs) in models of experimental pulse duplicator systems. An initial experimental validation of the models is demonstrated through comparisons to data on pressures, flow rates, and leaflet kinematics. The paper also contrasts the flow patterns and leaflet strains and stresses generated by porcine tissue and bovine pericardial BHVs.

Charles’ paper is on the arXiv

February 8, 2019

Charles’ paper, A sharp interface method for an immersed viscoelastic solid, is now available on the arXiv. This paper develops an extension of the hyperelastic immersed boundary method that sharply resolves pressure discontinuities at fluid-structure interfaces by modifying the definition of the elastic stress tensor associated with the hyperelastic material response. Unlike most other sharp-interface immersed boundary methods, however, this approach allows us to use standard discretization methods that are “oblivious” to the presence of the pressure discontinuity. Numerical tests show the impact of the method on the accuracy of the overall scheme, and an approach is developed that allows us to compute the splitting efficiently.