Chongam Kim

Chongam Kim
Seoul National University | SNU · Department of Aerospace Engineering

Doctor of Philosophy

About

237
Publications
26,523
Reads
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3,068
Citations
Citations since 2017
48 Research Items
1362 Citations
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
2017201820192020202120222023050100150200250
Introduction
- Computational fluid dynamics and Computational aerodynamics - Numerical methods & high-order methods for conservation laws - All-speed multi-phase flows - Fluid-structure interaction & Multi-disciplinary flow analysis - Aerodynamic shape optimization and Flow control
Skills and Expertise

Publications

Publications (237)
Article
View Video Presentation: https://doi.org/10.2514/6.2022-3924.vid In order to simulate hypersonic equilibrium flow, an infinitely differentiable air property model is developed based on an artificial neural network (ANN). Curve-fit models have been conventionally used to predict hypersonic reacting flow when local thermochemical equilibrium is assum...
Article
Notwithstanding the effectiveness of ventilated cavitation as a safe way to accelerate and achieve natural supercavitation, detailed physics of ventilated cavitating flows and hydrodynamic effects on underwater vehicles have been rarely explored. The present work deals with computational investigation on ventilated supercavitating flows around a hi...
Article
We present the experimental design optimization of a flapping wing and the development of a non-circular gear based flapping mechanism to enhance the propulsive efficiency of a flapping wing micro air vehicle (FWMAV). The proposed flapping mechanism consists of a very simple structure, which excludes any linkages but utilizes non-circular gears to...
Article
Full-text available
Cavitation in thermosensitive fluids is accompanied by a noticeable temperature drop inside a cavity. Motivated by the fact that most popular cavitation models have been developed without considering thermodynamic effects, the present study proposes physics-based corrections to existing cavitation models. Two primary corrections are adopting the ph...
Conference Paper
Full-text available
View Video Presentation: https://doi.org/10.2514/6.2021-2715.vid Direct reconstruction method (DRM) is applied to the high-order physical domain-based discontinuous Galerkin (DG) method. The resulting method, DRM-DG, is verified and intensively validated by various flow problems with different governing systems. DRM was originally proposed to addre...
Article
Sophisticated solution algorithms, along with complex data structures, are known as the main barriers that hinder high-order methods from being actively embraced by industry and academia. Simultaneously, modern computing machines offer a wide variety of opportunities to enhance the performance of solution algorithms through highly tuned computation...
Article
The present study deals with the code optimization and its implementation of the direct reconstruction method (DRM) using the complete-search tensor contraction (CsTC) framework to extract the best performance of high-order methods on modern computing architectures. DRM was originally proposed to overcome severe computational costs of the physical...
Conference Paper
This paper presents the development and assessment of ACTFlow, a target-oriented finite volume solver to simulate all-speed compressible turbulent flows on unstructured mixed-element grids. ACTFlow adopts state-of-the-art numerical components for spatial/temporal discretization and various levels of turbulence approximations. Code verification is c...
Article
The present work is to computationally analyze side loads in a thrust-optimized parabolic nozzle during high-altitude testing. The engine startup and shutdown processes of the Korean Space Launch Vehicle II third-stage rocket engine combustor are examined using three-dimensional time-accurate computations. The generation of side loads is closely re...
Article
Edge computing focuses on processing near the source of the data. Edge computing devices using the Tegra SoC architecture provide a physically distinct GPU memory architecture. In order to take advantage of this architecture, different modes of memory allocation need to be considered. Different GPU memory allocation techniques yield different resul...
Article
This study investigates the unsteady aerodynamic characteristics of the cambered wings of a flapping-wing micro air vehicle (FW-MAV) in hover. A three-dimensional fluid–structure interaction solver is developed for a realistic modeling of large-deforming wing structure and geometry. Cross-validation is conducted against the experimental results obt...
Article
Full-text available
In this study, a numerical analysis of pogo instability in liquid propulsion rockets was conducted and an optimization of the pogo suppressor was attempted. Pogo analysis was carried out using numerical results obtained via the major models for fuselage structure, feedline, and propulsion systems. In the structural system, the fuselage vibration mo...
Article
Shape optimization of modern three-dimensional hypersonic inlets requires many geometric design parameters. Because the flow physics is complex, a Reynolds-averaged Navier–Stokes (RANS) analysis is also desirable when performing optimization. A computationally efficient means of handling many-parameter optimization with expensive cost functions is...
Article
As the second extension of the direct reconstruction method (DRM), DRM for the surface integration of the discontinuous Galerkin (DG) weak formulation is presented on multi-dimensional high-order mixed meshes. From the previous study, DRM was successfully extended to the volume integration of the DG method, and produced a significant reduction in b...
Article
Full-text available
To understand cavity dynamics, many experimental and computational studies have been conducted for many decades. As computational methods, incompressible, isothermal compressible, and fully compressible flow solvers were used for the purpose. In the present study, to understand the compressibility effect on cavity dynamics, both incompressible and...
Article
This paper details the numerical investigations of bleed effects on supersonic inlet performance and buzz under various bleed conditions, including location, width, plenum static pressure, and inlet conditions (for example, inflow Mach number and throttling ratio). A bleed boundary condition model that reflects the effects of local flow expansion a...
Article
The goal of this work is to numerically investigate the mechanism of flow separation in a thrust-optimized parabolic nozzle during high-altitude testing. Both startup and shutdown processes of the Korea Space Launch Vehicle-II (KSLV-II) third-stage rocket engine are examined by axisymmetric computations. In particular, unconventional transitional p...
Article
Lateral thrust jets exhibit better maneuverability performance than control surfaces such as conventional fins for attitude control or the orbital transfer of guided weapons. In the supersonic region, however, jet interaction phenomena occur due to the lateral thrust jet during flight and a complicated flow structure is exhibited by the interaction...
Article
Full-text available
Despite their simple formulations, advection upstream splitting method (AUSM)-type flux schemes treat linear and nonlinear waves of complex flow fields in a robust and accurate manner. This paper presents the progress of AUSM-type fluxes augmented with pressure-based weight functions introduced by the authors and their colleagues. Starting from a f...
Article
This work deals with the development of the direct reconstruction method (DRM) and its application to the volume integration of the discontinuous Galerkin (DG) method on multi-dimensional high-order mixed-curved meshes. The conventional quadrature-based DG methods require the humongous computational cost on high-order curved elements due to their n...
Article
Full-text available
This paper presents an efficient and robust numerical framework to deal with multiphase real-fluid flows and their broad spectrum of engineering applications. A homogeneous mixture model incorporated with a real-fluid equation of state and a phase change model is considered to calculate complex multiphase problems. As robust and accurate numerical...
Article
The present paper deals with a new improvement of hierarchical multi-dimensional limiting process for resolving the subcell distribution of high-order methods on two-dimensional mixed meshes. From previous studies, the multi-dimensional limiting process (MLP) was hierarchically extended to the discontinuous Galerkin (DG) method and the flux reconst...
Article
Computations of all-speed multiphase real fluid flows for aerospace launch vehicles are known to be very demanding, owing to several issues that include robust capturing of two-phase shock/phase discontinuity and proper scaling of numerical flux at steady/unsteady all-speed flows. This paper deals with the development of computational components to...
Article
This paper focuses on the limitations of single-phase computations which have been widely applied to the numerical simulations of flow fields around thermal vapor compressors (TVCs), and provides computational improvements through multi-phase flow modeling and analysis. In order to capture the multi-phase flow physics accurately and provide reliabl...
Article
The present paper deals with the robust and accurate multi-dimensional limiting process for higher-order discontinuous Galerkin (DG) and flux resconstruction or correction procedure via reconstruction (FR/CPR) methods on tetrahedral meshes. MLP, which has been originally developed in finite volume method (FVM), provides an accurate, robust and effi...
Article
Full-text available
Recently, there has been an increase in the research on flapping wing vehicles which mimic biological motions. One result has been the flapping wing micro-aerial vehicle. In this paper, the design requirements for flapping wing micro-aerial vehicles were established through an analysis with the unsteady blade element theory. Then, based on the flap...
Article
This paper presents experimental and computational investigations of synthetic jets with a circular exit for improving flow control performance. First, the flow feature and vortex structure of a multiple serial circular exit were numerically analyzed from the view point of flow control effect under a cross flow condition. In order to improve separa...
Article
Full-text available
This paper deals with experimental investigation of active flow control via synthetic jets using an unmanned combat air vehicle (UCAV) planform. Fourteen arrays of synthetic jets, mounted along both leading edges, were fully or partially activated to increase aerodynamic efficiency and reduce pitch-up moment. The measurements were carried out using...
Article
The present paper deals with accuracy improvement of a bleed boundary condition model used to improve the performance of supersonic inlets. In order to accurately predict the amount of bleed mass flow rates, this study performs a scaling of sonic flow coefficient data for 90-degree bleed holes in consideration of Prandtl-Meyer expansion theory. Fur...
Research
Full-text available
Hierarchical multi-dimensional limiting process (MLP) is improved and extended for flux reconstruction or correction procedure via reconstruction (FR/CPR) on unstructured grids. MLP was originally developed in finite volume method (FVM) and it provides an accurate, robust and efficient oscillation-control mechanism in multiple dimensions for linear...
Article
Full-text available
To study the cavity dynamics behind a two-dimensional wedge, a pressure-based numerical solver for incompressible cavitating flow and a density-based numerical solver for compressible cavitating flow solvers were developed, respectively, using a cell-cantered finite volume method. Cavity interface was captured based on an approximation of homogeneo...
Article
Full-text available
The present study deals with a numerical method for cryogenic cavitating flows. Recently, we have developed an accurate and efficient baseline numerical scheme for all-speed water-gas two-phase flows. By extending such progress, we modify the numerical dissipations to be properly scaled so that it does not show any deficiencies in low Mach number r...
Article
Flow characteristics of synthetic jet based flow supplying devices have been computationally investigated for different device shapes. Jet momentum was produced by the volume change of a cavity by two piezoelectric-driven diaphragms. The devices have additional flow path compared with the original synthetic jet actuator, and these flow path changes...
Article
The present paper deals with the efficient computation of higher-order CFD methods for compressible flow using graphics processing units (GPU). The higher-order CFD methods, such as discontinuous Galerkin (DG) methods and correction procedure via reconstruction (CPR) methods, can realize arbitrary higher-order accuracy with compact stencil on unstr...
Article
Fully integrated computational simulations inside solid-propellant rockets are carried out to examine the nonlinear feedback interaction between fluid, structure, and burning module. The arbitrary Lagrangian Eulerian description is employed to efficiently track the burning process along the grain surface. An automatic remeshing algorithm is added t...
Article
During multi-physics or multi-phase simulations accompanying fluid- structure- thermal interaction, data transfer problems always arise along non- matching interfaces caused by different computational meshes for each physical domain. Common- refinement scheme, among many available methods, is attractive since it is known to yield conservative and a...
Conference Paper
Higher-order multi-dimensional limiting Process (MLP) [J. S. Park and C. Kim, Higher- order Multi-dimensional Limiting Strategy for Discontinuous Galerkin Methods in Com- pressible Inviscid and Viscous Flows, Comp. & Fluids, In press] is improved and applied to correction procedure via reconstruction (CPR) on unstructured grids. MLP, which has been...
Article
The present paper deals with the extension of AUSMPW+ scheme into two-fluid model for multiphase flow. AUSMPW+ scheme is the improvement of a single-phase AUSM+ scheme by designing pressure-based weighting functions to prevent oscillations near a wall and shock instability after a strong shock. Recently, Kitamura and Liou assessed a family of AUSM-...
Conference Paper
This paper deals with the numerical computations of cryogenic cavitating flows around turbopump inducer in liquid rocket. Recently, accurate and efficient baseline numerical schemes have been developed for the computations of all-speed two-pahse flows. The baseline numerical schemes - RoeM and AUSMPW+ schemes for multi-phase flows - are extended fo...
Conference Paper
This paper investigates the unsteady aerodynamic features of wing-body-vortex interactions and the effects of geometric factors such as wing shape and body angle in insects' flapping motions under forward flight condition. A realistic wing trajectory, called the 'figure-of-eight' motion, is extracted from a blowfly (Phormia regina)'s tethered fligh...
Article
All around the world, numerous scientists have been carried out researches of e-Science to improve performance of computations and accessibility of their experimental flexibilities for a long times. However, they still have been in difficulty securing high-performance computing facilities. In case of Aerodynamics, for example, a single experiment c...
Conference Paper
This paper deals with an adjoint-based design optimization of vortex generators to control a junction vortex of wing-body aircraft. The target geometry is the DLR-F6, which is known to have some undesirable flow features caused by a wing-body junction vortex; thus, a vortex generator was adopted and optimized to eliminate the junction vortex withou...
Article
Full-text available
The present paper deals with concept design of supersonic inlet based on compressible flow theory and flow control of bleeding in order to guarantee stability of supersonic inlet of ramjet engine in broad range of operating conditions. Shock instability, shock wave-boundary layer interaction and flow separation should be properly controlled to impr...
Article
This paper deals with an adjoint-based design optimization of vortex generators for the performance improvement of an S-shaped subsonic inlet, the Royal Aircraft Establishment intake model 2129. To enhance the flow quality entering the engine face maximally, the vortex generators are independently optimized with five design parameters per each vort...
Article
The purpose of this paper is the evaluation of the flutter onset velocity acting on a moving bridge deck section using a web-based distributed computing environment, namely e-WINDS. e-WINDS, an abbreviation of ‘e-Wind flow Investigation & Design Systems’, is a virtual organization supporting CFD (Computational Fluid Dynamics) simulations for the us...
Article
This paper deals with an efficient and high-fidelity design strategy for wing-body configuration. According to the nature of the design space and the number of design variables, aerodynamic shape optimization is carried out at each design stage by using a selective optimization strategy. In the first stage, global optimization techniques are applie...
Article
Full-text available
A series of numerical simulations are carried out to analyze a supersonic inlet buzz, which is an unsteady pressure oscillation phenomenon around a supersonic inlet. A simple but efficient geometry, experimentally adopted by Nagashima, is chosen for the analysis of unsteady flow physics. Among the two sets of simulations considered in this study, t...
Conference Paper
This paper presents a transient time aeroelastic analysis for a supersonic flight vehicle with a ramjet engine. First, computational fluid dynamics (CFD) is conducted to estimate its baseline geometry and the prediction results obtained upon the vehicle surface are transferred to the structural transient time analysis. The structural analysis is th...
Article
Synthetic jets have been widely used for flow control applications and heat-transfer enhancements. A significant amount of research has been carried out on formation, evolution, and interaction of a synthetic jet under various flow conditions. This paper presents experimental and computational investigations on the characteristics of synthetic jets...
Conference Paper
This paper investigates the unsteady aerodynamic features of wing-wing, wing-body and vortex-vortex interactions in insects' flapping motions under forward flight condition. A realistic wing trajectory, called the 'figure-of-eight' motion, is extracted from a blowfly (Phormia regina)'s tethered flight experiment under the freestream velocity of 2.7...
Conference Paper
A fluid-structure interaction of solid propellant rocket interior is carried out by employing the ALE (Arbitrary Lagrangian Eulerian) description, a hybrid model of continuum motion description combining the advantages of classical Lagrangian and Eulerian description. The fluid-structure interaction process and an automatic re-meshing algorithm are...
Article
Designing a scientific workflow for a complicated scientific application is now a trend to make the management of the problem simple and reuse the experiment for other simulations. Scientific workflow automates a repetitive cycle of transferring data and performing complex operations in a straightforward way in order to make it easier for scientist...
Conference Paper
Full-text available
The advent of cloud computing makes scientists to extend their research environments over supercomputers to on-demand and dynamically scalable resources. Science cloud becomes a trend in various scientific domains these days. However, it is difficult to provide optimal job execution environment rapidly and dynamically depending on user's demands. T...
Conference Paper
Full-text available
Due to diverse characteristics of application domains, most experts dealing with scientific computational simulations require a specialized and customized Problem Solving Environment (PSE) with easy-to-use graphical user interfaces integrated with large-scale computing resources for their experiments. It is also important to provide adequate middle...
Article
The flow characteristics of synthetic jet depending on rectangular and circular jet exit configuration are investigated using numerical computation with cross flow. In rectangular slot, synthetic jet generates the strong vortex but supplies fewer momentum and effectiveness of flow control is reduced along flow direction. In circular slot, regular v...
Conference Paper
This paper deals with the adjoint-based design optimization of vortex generators for the performance improvement of the subsonic inlet. The RAE M2129, an S-shaped inlet, was selected as the target geometry. Because of the differences in radius of curvature between the port side (outer wall) and starboard side (inner wall), a centrifugal pressure gr...
Conference Paper
This paper deals with the continuous efiorts of extending the multi-dimensional limiting process (MLP) for high speed compressible flows (or hyperbolic conservation laws), Which has been quite successful in finite volume methods (FVM), into discontinuous Galerkin (DG) methods. From the previous works, it was observed that the MLP shows several supe...
Article
This paper investigates the unsteady flowfield characteristics around three-dimensional insect flapping motion under forward flight conditions. A realistic wing trajectory, called the "figure-of-eight" motion, is extracted from a blowfly's (phormia regina) tethered flight experiment under a freestream velocity of 2.75 m/s. In the authors' prelimina...
Article
Flow control using synthetic jets has been computationally investigated to improve aerodynamic performance of tiltrotor unmanned-aerial-vehicle airfoils under various flight conditions. Many features of complex tiltrotor flows were captured, including wing leading-edge and trailing-edge separation and the massive region of separated flow beneath th...
Article
Interaction between a flexible flapping wing and the ambient fluid is of considerable importance in realistic flapping flight. In this paper, two-dimensional fluid structure interaction simulations are conducted to examine realistic flow features of insects' flapping motion and to investigate aerodynamic change due to structural flexibility of inse...