Engr Res Assoc, Mechanical Engineering
- The effects of clinically-derived parametric data uncertainty in patient-specific coronary simulations with deformable walls arXiv:1908.07522 2019
Turbulent flows over superhydrophobic surfaces: flow-induced capillary waves, and robustness of air-water interfaces.
JOUNRNAL OF FLUID MECHANICS
2018; 835: 45–85
View details for DOI 10.1017/jfm.2017.733
- Pressure fluctuations and interfacial robustness in turbulent flows over superhydrophobic surfaces JOURNAL OF FLUID MECHANICS 2015; 783: 448-473
Fluid-structure interaction simulations of patient-specific aortic dissection.
Biomechanics and modeling in mechanobiology
Credible computational fluid dynamic (CFD) simulations of aortic dissection are challenging, because the defining parallel flow channels-the true and the false lumen-are separated from each other by a more or less mobile dissection membrane, which is made up of a delaminated portion of the elastic aortic wall. We present a comprehensive numerical framework for CFD simulations of aortic dissection, which captures the complex interplay between physiologic deformation, flow, pressures, and time-averaged wall shear stress (TAWSS) in a patient-specific model. Our numerical model includes (1) two-way fluid-structure interaction (FSI) to describe the dynamic deformation of the vessel wall and dissection flap; (2) prestress and (3) external tissue support of the structural domain to avoid unphysiologic dilation of the aortic wall and stretching of the dissection flap; (4) tethering of the aorta by intercostal and lumbar arteries to restrict translatory motion of the aorta; and a (5) independently defined elastic modulus for the dissection flap and the outer vessel wall to account for their different material properties. The patient-specific aortic geometry is derived from computed tomography angiography (CTA). Three-dimensional phase contrast magnetic resonance imaging (4D flow MRI) and the patient's blood pressure are used to inform physiologically realistic, patient-specific boundary conditions. Our simulations closely capture the cyclical deformation of the dissection membrane, with flow simulations in good agreement with 4D flow MRI. We demonstrate that decreasing flap stiffness from [Formula: see text] to [Formula: see text] kPa (a) increases the displacement of the dissection flap from 1.4 to 13.4 mm, (b) decreases the surface area of TAWSS by a factor of 2.3, (c) decreases the mean pressure difference between true lumen and false lumen by a factor of 0.63, and (d) decreases the true lumen flow rate by up to 20% in the abdominal aorta. We conclude that the mobility of the dissection flap substantially influences local hemodynamics and therefore needs to be accounted for in patient-specific simulations of aortic dissection. Further research to accurately measure flap stiffness and its local variations could help advance future CFD applications.
View details for DOI 10.1007/s10237-020-01294-8
View details for PubMedID 31993829
- Multi-fidelity estimators for coronary circulation models under clinically-informed data uncertainty International Journal for Uncertainty Quantification. 2020
Performance of preconditioned iterative linear solvers for cardiovascular simulations in rigid and deformable vessels.
2019; 64: 717–39
Computing the solution of linear systems of equations is invariably the most time consuming task in the numerical solutions of PDEs in many fields of computational science. In this study, we focus on the numerical simulation of cardiovascular hemodynamics with rigid and deformable walls, discretized in space and time through the variational multiscale finite element method. We focus on three approaches: the problem agnostic generalized minimum residual (GMRES) and stabilized bi-conjugate gradient (BICGS) methods, and a recently proposed, problem specific, bi-partitioned (BIPN) method. We also perform a comparative analysis of several preconditioners, including diagonal, block-diagonal, incomplete factorization, multigrid, and resistance based methods. Solver performance and matrix characteristics (diagonal dominance, symmetry, sparsity, bandwidth and spectral properties) are first examined for an idealized cylindrical geometry with physiologic boundary conditions and then successively tested on several patient-specific anatomies representative of realistic cardiovascular simulation problems. Incomplete factorization preconditioners provide the best performance and results in terms of both strong and weak scalability. The BIPN method was found to outperform other methods in patient-specific models with rigid walls. In models with deformable walls, BIPN was outperformed by BICG with diagonal and Incomplete LU preconditioners.
View details for DOI 10.1007/s00466-019-01678-3
View details for PubMedID 31827310
View details for PubMedCentralID PMC6905469
Effect of texture randomization on the slip and interfacial robustness in turbulent flows over superhydrophobic surfaces
PHYSICAL REVIEW FLUIDS
View details for DOI 10.1103/PhysRevFluids.3.044601
- On the scaling of the slip velocity in turbulent flows over superhydrophobic surfaces PHYSICS OF FLUIDS 2016; 28 (2)