About

George Ilhwan Park, Ph.D., is an Assistant Professor in the Department of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania. He leads the Park Lab at Penn, where his research focuses on advanced computational methods in fluid mechanics, particularly wall-modeled large-eddy simulation (WMLES) technology. His work includes the evaluation and application of WMLES to complex turbulent boundary layers, including statistically three-dimensional boundary layers and flows with pressure gradients. Professor Park's research also extends to fluid-structure interaction problems, with applications in cardiovascular mechanics, and low Reynolds number aerodynamics relevant to small-scale flying robots. His group has been recognized for securing significant high-end computing resources to advance their simulations, including a project on a NASA supercomputer. Professor Park actively engages with the scientific community through seminars and workshops, sharing insights on the feasibility of aircraft LES on exascale computing platforms and the requirements for advanced computational methods in scientific grand challenges.

Research topics

• Engineering
• Computer Science
• Geodesy
• Aerospace engineering
• Geology
• Optoelectronics
• Materials science
• Composite material
• Physics
• Electrical engineering
• Mechanics

Selected publications

• Effects of NaCl Solution on Proton Exchange Membrane Fuel Cell with Serpentine Flow Channel of Different Depths

  Journal of the Korean Society for Precision Engineering · 2025-05-01

  articleOpen access

  Degradation of proton exchange membrane fuel cells (PEMFCs) can be accelerated by impurities in the air. In maritime environments in particular, sodium chloride (NaCl) can reduce the performance of membrane electrode assembly (MEA) in PEMFCs. In this context, we experimentally analyzed effect of flow channel depth on PEMFCs humidified with a NaCl solution at the cathode side. The analysis was conducted in serpentine flow channels with different depths of 0.4, 0.8, and 1.6 mm. The initial performance of unit cells was compared to their performance after applying a constant current for 10 hours. Results showed that the degradation rate correlated positively with the flow-channel depth. Channel depths of 0.4 and 1.6 mm resulted in 2.4% and 7.3% decreases in the maximum power density, respectively. For the 1.6 mm channel depth, the activation loss after 10 hours was larger than the initial loss.

  PublisherDOI

• The Evolution of Turbulence Producing Motions in the Neutral ABL Across a Natural Roughness Transition

  Journal of Geophysical Research Atmospheres · 2025-03-04 · 2 citations

  articleOpen accessSenior author

  Abstract Landforms such as sand dunes act as roughness elements to Atmospheric Boundary Layer (ABL) flows, triggering the development of new scales of turbulent motions. These turbulent motions, in turn, energize and kick‐up sand particles, influencing sediment transport and ultimately the formation and migration of dunes—with knock‐on consequences for dust emission. While feedback between flow and form have been studied at the scale of dunes, research has not examined how the development of an Internal Boundary Layer (IBL) over the entire dune field influences sediment‐transporting turbulence. Here, we deploy a large‐eddy simulation of an ABL encountering a natural roughness transition: the sand dunes at White Sands National Park, New Mexico. We analyze turbulence producing motions and how they change as the IBL grows over the dune field. Frequency spectrum and Reynolds shear stress profiles show that IBL thickness determines the largest scales of turbulence. Moreover, the developing IBL enhances the frequency, magnitude and duration of sweep and ejection events—turbulence producing motions whose peaks systematically migrate away from the wall as the IBL thickens. Because sweep and ejection events are known to drive sediment transport, our findings provide a mechanism for coupling the co‐evolution of the landscape and the ABL flow over it. More broadly, our results have implications for how roughness transitions influence the transport of pollutants, particulates, heat, and moisture.

  PublisherOA PDFDOI

• Physics-based distinction of nonequilibrium effects in near-wall modeling of turbulent separation bubble with and without sweep

  Physical Review Fluids · 2025-10-14

  articleSenior author

  Three-dimensional turbulent boundary layers subject to pressure gradients and undergoing separation remain a key challenge for wall modeling. Using DNS datasets of swept and unswept separation bubbles, this study employs the Renard--Deck skin-friction decomposition to isolate and analyze nonequilibrium contributions critical to near-wall modeling. Wall-modeled LES demonstrates that only wall models capturing the spatial growth term accurately reproduce the true energy balance in nonequilibrium zones. The analysis highlights when and why nonequilibrium effects must be incorporated, providing physics-based guidance for improving wall model predictions in practical flows.

  PublisherDOI

• On the grid convergence of wall-modeled large-eddy simulation

  Journal of Computational Physics · 2024-02-29 · 10 citations

  articleSenior authorCorresponding
  PublisherDOI

• An Immersed Fluid-Structure Interaction Method Targeted for Heart Valve Applications

  SSRN Electronic Journal · 2024-01-01

  preprintOpen accessSenior author
  PublisherDOI

• The hydraulically smooth limit of flow over surfaces with spanwise heterogeneity

  International Journal of Heat and Fluid Flow · 2024-08-17 · 3 citations

  article
  PublisherDOI

• An Alternative Scaling for Roughness Transitions in Turbulent Flows: The Role of the Internal Boundary Layer

  arXiv (Cornell University) · 2024-11-13

  preprintOpen access

  When turbulent boundary layer flows encounter abrupt roughness changes, an Internal Boundary Layer (IBL) forms. Equilibrium theory breaks down in the nonequilibrium IBL, which may extend O(10) km for natural atmospheric flows. Here, we find that the IBL possesses a characteristic time-scale associated with the IBL height, $δ_i$. We show that $δ_i$ and the edge velocity set the scales of the mean and defect velocity profiles within the IBL, for simulation and experimental data covering a multitude of roughness transition types. We present a nontrivial extension of equilibrium theory to the dynamically adjusting IBL, which can be useful for modeling a range of environmental and industrial flows.

  PublisherOA PDFDOI

• Linear stability analysis of oblique Couette–Poiseuille flows

  Journal of Fluid Mechanics · 2024-10-29 · 2 citations

  articleOpen accessSenior authorCorresponding

  We perform a detailed numerical study of modal and non-modal stability in oblique Couette–Poiseuille profiles, which are among the simplest examples of three-dimensional boundary layers. Through a comparison with the Orr–Sommerfeld operator for the aligned case, we show how an effective wall speed succinctly characterizes modal stability. Large-scale parameter sweeps reveal that the misalignment between the pressure gradient and wall motion is, in general, destabilizing. For flows that are sufficiently oblique, the instability is found to depend exclusively on the direction of wall motion and not on its speed, a conclusion supported, in part, by the perturbation energy budget and the evolution of the critical layers. Closed forms for the critical parameters in this regime are derived using a simple analysis. From a non-modal perspective, pseudoresonance is examined through the resolvent and the $\epsilon$ -pseudospectra. An analysis of the unforced initial value problem shows that the maximum energy gain is highly dependent on both the magnitude and direction of the wall velocity. However, the strongest amplification is always achieved for configurations that are only weakly skewed. Finally, the optimal perturbations appear to develop via a lift-up effect enhanced by an Orr-like mechanism, the latter driven by cross-flow shear.

  PublisherOA PDFDOI

• Linear Stability Analysis of Oblique Couette-Poiseuille flows

  arXiv (Cornell University) · 2024-02-11

  preprintOpen accessSenior author

  We perform a detailed numerical study of modal and non-modal stability in oblique Couette-Poiseuille profiles, which are among the simplest examples of three-dimensional boundary layers. Through a comparison with the Orr-Sommerfeld operator for the aligned case, we show how an effective wall speed succinctly characterizes modal stability. Large-scale parameter sweeps reveal that the misalignment between the pressure gradient and wall motion is, in general, destabilizing. For flows that are sufficiently oblique, the instability is found to depend exclusively on the direction of wall motion and not on its speed, a conclusion supported, in part, by the perturbation energy budget and the evolution of the critical layers. Closed forms for the critical parameters in this regime are derived using a simple analysis. Finally, a modified long-wavelength approximation is developed, and the resulting asymptotic eigenvalue problem is used to show that there is no cutoff wall speed for unconditional stability whenever the angle of wall motion is non-zero, in stark contrast to the aligned case. From a non-modal perspective, pseudo-resonance is examined through the resolvent and the $ε$-pseudospectra. An analysis of the unforced initial value problem shows that the maximum energy gain is highly dependent on both the magnitude and direction of the wall velocity. However, the strongest amplification is always achieved for configurations that are only weakly skewed. Finally, the optimal perturbations appear to develop via a lift-up effect induced by an Orr-like mechanism.

  PublisherOA PDFDOI

• Revisiting crossflow-based stabilization in channel flows

  Physical Review Fluids · 2024-11-18 · 1 citations

  articleSenior author

  Fluid suction/injection through porous boundaries is a classic strategy for boundary-layer control. However, its utility in channel flows is comparatively ambiguous. Using two canonical configurations, we show that non-modal perturbations well below the linear instability threshold are heavily amplified by weak vertical crossflows. Only very strong (thus costly) crossflows can sufficiently inhibit modal and non-modal instabilities. However, these are shown to be accompanied by declining mass flow rates, deprecating any apparent advantage. Our results challenge previous literature and the suitability of crossflow-based control in internal flows.

  PublisherDOI

Frequent coauthors

• Parviz Moin

  Stanford University

  25 shared

• Xiang I. A. Yang

  Pennsylvania State University

  12 shared

• Sanjeeb Bose

  Cadence Design Systems (United States)

  7 shared

• Yuanwei Bin

  Pennsylvania State University

  7 shared

• Imran Hayat

  University of Pennsylvania

  7 shared

• Adrián Lozano-Durán

  7 shared

• Yu Lv

  University of Chinese Academy of Sciences

  5 shared

• D. J. Jerolmack

  5 shared

Labs

• Park Lab @ PennPI

  Principal Investigator George Ilhwan Park, Ph.D. Assistant Professor Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania PICS Rm 524A3401 Walnut St, Philadelphia, PA, 19104 gipark@seas.upenn.edu / +1-215-898-5596 CV

Education

• Ph.D., Mechanical Engineering

  University of California, Berkeley

  2015

• M.S., Mechanical Engineering

  University of California, Berkeley

  2011

• B.S., Mechanical Engineering

  University of California, Berkeley

  2010