Academic Appointments


  • Research Engineer, Mechanical Engineering

Honors & Awards


  • Kwanjeong Scholarship, Kwanjeong Educational Foundation (2012)
  • Jungsong Scholarship, Jungsong Foundation (2010)
  • Summa Cum Laude, Seoul National University (2010)

Professional Education


  • Postdoctoral Scholar, Stanford University, School of Medicine (2019)
  • Ph.D., Stanford University, Mechanical Engineering (2017)
  • M.S., Stanford University, Mechanical Enigineering (2012)
  • B.S., Seoul National University, Mechanical Engineering (2010)

Current Research and Scholarly Interests


CARDIOVASCULAR MODELING AND SIMULATION, FLUID MECHANICS, UQ, TURBULENCE.

Projects


  • Computational evaluation of venous graft geometries in coronary artery bypass surgery, Stanford University

    Location

    California

    Collaborators

    • Alison Marsden, Associate Professor of Pediatrics (Cardiology) and of Bioengineering and, by courtesy, of Mechanical Engineering, Stanford University
    • Andrew Kahn, Professor, University of San Diego
    • Abhay Ramanchandra, Postdoctoral Scholar, Yale University
    • Jack Boyd, Professor, Stanford University School of Medicine
  • Uncertainty quantification in patient-specific cardiovascular simulation, Stanford University

    Location

    California

    Collaborators

    • Alison Marsden, Associate Professor of Pediatrics (Cardiology) and of Bioengineering and, by courtesy, of Mechanical Engineering, Stanford University
    • Daniele Schiavazzi, Assistant Professor, University of Notre Dame
    • Andrew Kahn, Professor, University of California San Diego School of Medicine
    • Casey Fleeter, Ph.D. Student in Computational and Mathematical Engineering, admitted Autumn 2015, School of Engineering
  • Passive and Active Friction Drag Reduction of Turbulent Flows Over Superhydrophobic Surfaces, Stanford University

    Location

    CA

    Collaborators

    • Ali Mani, Associate Professor of Mechanical Engineering, Stanford University
    • Ricardo GarciaMayoral, Lecturer, University of Cambridge

All Publications


  • The effects of clinically-derived parametric data uncertainty in patient-specific coronary simulations with deformable walls. International journal for numerical methods in biomedical engineering Seo, J., Schiavazzi, D. E., Kahn, A. M., Marsden, A. L. 2020

    Abstract

    Cardiovascular simulations are increasingly used for non-invasive diagnosis of cardiovascular disease, to guide treatment decisions, and in the design of medical devices. Quantitative assessment of the variability of simulation outputs due to input uncertainty is a key step toward further integration of cardiovascular simulations in the clinical workflow. In this study, we present uncertainty quantification in computational models of the coronary circulation to investigate the effect of uncertain parameters, including coronary pressure waveform, intramyocardial pressure, morphometry exponent, and the vascular wall Young's modulus. We employ a left coronary artery model with deformable vessel walls, simulated via an Arbitrary-Lagrangian-Eulerian framework for fluid-structure interaction, with a prescribed inlet pressure and open-loop lumped parameter network outlet boundary conditions. Stochastic modeling of the uncertain inputs is determined from intracoronary catheterization data or gathered from the literature. Uncertainty propagation is performed using several approaches including Monte Carlo, Quasi Monte Carlo sampling, stochastic collocation, and multiwavelet stochastic expansion. Variabilities in the quantities of interest, including branch pressure, flow, wall shear stress, and wall deformation are assessed. We find that uncertainty in inlet pressures and intramyocardial pressures significantly aect all resulting QoIs, while uncertainty in elastic modulus only affects the mechanical response of the vascular wall. Variability in the morphometry exponent used to distribute the total downstream vascular resistance to the single outlets, has little effect on coronary hemodynamics or wall mechanics. Finally, we compare convergence behaviors of statistics of QoIs using several uncertainty propagation methods on three model benchmark problems and the left coronary simulations. From the simulation results, we conclude that the multi-wavelet stochastic expansion shows superior accuracy and performance against Quasi Monte Carlo and stochastic collocation methods. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/cnm.3351

    View details for PubMedID 32419369

  • Turbulent flows over superhydrophobic surfaces: flow-induced capillary waves, and robustness of air-water interfaces. JOUNRNAL OF FLUID MECHANICS Seo, J., Garcia-Mayoral, R., Mani, A. 2018; 835: 45–85

    View details for DOI 10.1017/jfm.2017.733

  • On the scaling of the slip velocity in turbulent flows over superhydrophobic surfaces PHYSICS OF FLUIDS Seo, J., Mani, A. 2016; 28 (2)

    View details for DOI 10.1063/1.4941769

    View details for Web of Science ID 000371286500052

  • Pressure fluctuations and interfacial robustness in turbulent flows over superhydrophobic surfaces JOURNAL OF FLUID MECHANICS Seo, J., Garcia-Mayoral, R., Mani, A. 2015; 783: 448-473
  • Fluid-structure interaction simulations of patient-specific aortic dissection. Biomechanics and modeling in mechanobiology Baumler, K., Vedula, V., Sailer, A. M., Seo, J., Chiu, P., Mistelbauer, G., Chan, F. P., Fischbein, M. P., Marsden, A. L., Fleischmann, D. 2020

    Abstract

    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

  • Computational evaluation of venous graft geometries in coronary artery bypass surgery Seo, J., Ramanchandra, A. B., Boyd, J., Kahn, A., Marsden, A. In preparation. 2020

    Abstract

    Coronary artery bypass graft (CABG) surgery with vein grafts is the current mainstay of multivessel revascularization in coronary artery disease. Cardiothoracic surgeons are faced with a choice of different revascularization techniques for saphenous venous grafts (SVG), each with varying outcomes. Further, the effect of the vein graft geometry on the outcomes of these techniques has not been fully explored. Using computational simulations we systematically compare hemodynamics of the single, Y, and sequential configurations in CABG patient-specific models. We virtually investigate the effect of SVG diameters on hemodynamics of both venous grafts and the target coronary arteries. We use patient-specific cardiovascular modeling pipeline to generate three-dimensional anatomic geometric model of CABG patients and quantify mechanical stimuli. We perform virtual surgery on three patient-specific models by modifying the geometry of the vein graft to reflect either a single, Y, or sequential surgical configuration. In addition, the diameter of the SVG was virtually varied from 2mm to 5mm. Our study demonstrates that the coronary artery runoffs are relatively insensitive to the choice of the revascularization geometry of the SVG. We observe a 10% increase of runoff when the diameter of SVG is changed from 2mm to 5mm. The WSS of SVG increases dramatically when the diameter becomes small, following the inverse cube scaling of diameter. For a fixed diameter, the sequential configuration shows the lowest wall shear stress on the vein graft compared to Y and single grafts. Based on the inverse cube scaling of diameter, it is demonstrated that the sequential grafts with 2mm diameter is exposed to high wall shear stress ≽ 20 dyne/cm2, and the single grafts with 4mm diameter is exposed to low wall shear stress ≼ 4 dynes/cm2.

  • Multi-fidelity estimators for coronary artery circulation models under clinically-informed data uncertainty International Journal for Uncertainty Quantification Seo, J., Fleeter, C., Kahn, A. M., Marsden, A. L., Schiavazzi, D. 2020
  • Performance of preconditioned iterative linear solvers for cardiovascular simulations in rigid and deformable vessels. Computational mechanics Seo, J., Schiavazzi, D. E., Marsden, A. L. 2019; 64: 717–39

    Abstract

    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 Seo, J., Mani, A. 2018; 3