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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!

Mike’s paper is accepted for publication in JTCVS Open

September 15, 2020

Mike’s paper with Robert and others, Bioprosthetic aortic valve diameter and thickness are directly related to leaflet fluttering: Results from a combined experimental and computational modeling study, has been accepted to appear in JTCVS Open, the open-access mirror of the Journal of Thoracic and Cardiovascular Surgery. This study demonstrates that bioprosthetic heart valves with smaller diameters and/or thicker leaflets generate higher fluttering frequencies in experimental and computational pulse duplicators. Because fluttering can impair the durability of flexible structures, extensions of this work may ultimately lead to new device design targets or selection guidelines to improve the durability of valve replacement.

Congratulations, Mike!

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!

Congratulations to Drs. Fuhui Fang and Mike Lee!

July 16, 2020

Congratulations to Fuhui Fang and Mike Lee for successfully completing their PhDs.

Fuhui’s thesis is on Numerical Advances for Fluid-Structure Interactions in Entangled Polymer Solutions with Applications to Active Microbead Rheology. Fuhui will be starting a position at Microsoft in the Fall.

Mike’s thesis is on Simulating In Vitro Models of Cardiovascular Fluid-Structure Interaction: Methods, Models, and Applications. Mike is off to a postdoctoral position at Johns Hopkins in the Department of Mechanical Engineering and Institute for Computational Medicine.

Good luck, Fuhui and Mike!

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.

Congratulations to Dr. Yanni Lai!

December 15, 2019

Congratulations to Yanni Lai for successfully completing her PhD. Yanni’s thesis was on Multigrid Methods for the Bidomain Equations. Yanni has already started a position at Amazon in Seattle. Good luck, Yanni!