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Chun-Hian Lee

Bio: Chun-Hian Lee is an academic researcher from Beihang University. The author has contributed to research in topics: Boundary layer & Supersonic speed. The author has an hindex of 13, co-authored 82 publications receiving 592 citations. Previous affiliations of Chun-Hian Lee include China Aerospace Science and Technology Corporation & National Laboratory for Computational Fluid Dynamics.


Papers
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Journal ArticleDOI
TL;DR: In this article, the effects of two different 11-species chemical reaction models on hypersonic reentry flow simulations are numerically investigated, and two typical configurations, the RAM-C II vehicle and FIRE II capsule, are selected as test cases, whose thermo-chemical nonequilibrium flowfields are computed by a multi-block finite volume code using a two-temperature model (a translational-rotational temperature and a vibrational-electron-electronic temperature).

58 citations

Journal ArticleDOI
TL;DR: AUSMDV and k-ω SST turbulence model with an explicit compressibility correction was developed, and a 3-D numerical simulation of a supersonic flow field with a vertical sonic jet of hydrogen was performed as mentioned in this paper.
Abstract: A numerical method using AUSMDV scheme and k-ω SST turbulence model with an explicit compressibility correction was developed, and a 3-D numerical simulation of a supersonic flow field with a vertical sonic jet of hydrogen was performed Good agreement between numerical results and experimental data validated the reliability of the numerical method Whereafter, two parameters, mass-weighted average total pressure and mixing efficiency, were defined to evaluate the mixing performance of different injection schemes Based on the numerical method and evaluation criterion, the mixing characteristics of different injection schemes were studied in detail It was found that for the mixing field of supersonic transverse jet, the near-field mixing is controlled by convection transport while the far-field mixing is controlled by mass diffusion; the circular-hole injection causes a loss of total pressure comparable to the slot injection, but can induce a much higher mixing efficiency because of its 3-D flow characteristic; the variation of injection angle under circular-hole injection mainly affects the near-field mixing degree, and among the five injection angles studied in the present paper, angle 120° is the optimal one; with the increase of the ratio between injector space and diameter, the induced mixing efficiency increases while the caused loss of total pressure can grow greatly; the two-stage injection method designed through reducing the injector area to keep the same hydrogen mass flowrate can induce a much higher mixing efficiency while only a bit larger loss of total pressure when compared to the single-stage injection, and hence the two-stage injection is superior to the single-stage injection The research results can direct the design of the fuel injection method in the combustor of scramjet engine

45 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of heat release by the hydrogen combustion in supersonic turbulent boundary layers is numerically studied using Reynolds-averaged Navier-Stokes equations.
Abstract: Influences of heat release by the hydrogen combustion in supersonic turbulent boundary layers are numerically studied using Reynolds-averaged Navier–Stokes equations. The adopted Reynolds-averaged Navier–Stokes methodology is first validated by comparing the numerical results with the existing experimental data. Studies on the effects of the flame perpendicular position inside the boundary layer reveal that, while the flame is restricted around the edge of the boundary layer, the heat release may slightly reduce rather than increase the wall heat flux because of the suppression effect on the turbulent energy transport due to heat release. However, as the flame moves toward the wall, the skin-friction reduction effect would not be obviously strengthened, but the wall heat flux could be dramatically enhanced by the increase of near-wall chemical reactions. At a given hydrogen mass flow rate, the injection scheme with a higher injection height and a lower injection velocity could be helpful to achieve a larg...

42 citations

Journal ArticleDOI
TL;DR: A multi-wave approximation on rarefaction fan is proposed to avoid the occurrences of raref action shocks in computations and Computational efficiency comparisons show that the developed scheme is capable of reducing the computational time effectively with increasing the time step.

38 citations


Cited by
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01 Jan 1993
TL;DR: In this article, particle-in-cell (PIC) combined with Monte Carlo collision (MCC) calculations are used for simulation of partially ionized gases, with many of the features met in low-temperature collision plasmas.
Abstract: Many-particle charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. The author emphasizes the development of PIC computer experiments since the 1950s starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. Details are provided for adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collision plasmas; for example, with applications to plasma-assisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas. >

1,022 citations

01 Nov 1960

455 citations

Journal ArticleDOI
TL;DR: The study shows that the criteria employed for assessing the face mask performance must be modified to take into account the penetration dynamics of airborne droplet transmission, the fluid dynamics leakage around the filter, and reduction of efficiency during cough cycles.
Abstract: Face mask filters-textile, surgical, or respiratory-are widely used in an effort to limit the spread of airborne viral infections. Our understanding of the droplet dynamics around a face mask filter, including the droplet containment and leakage from and passing through the cover, is incomplete. We present a fluid dynamics study of the transmission of respiratory droplets through and around a face mask filter. By employing multiphase computational fluid dynamics in a fully coupled Eulerian-Lagrangian framework, we investigate the droplet dynamics induced by a mild coughing incident and examine the fluid dynamics phenomena affecting the mask efficiency. The model takes into account turbulent dispersion forces, droplet phase-change, evaporation, and breakup in addition to the droplet-droplet and droplet-air interactions. The model mimics real events by using data, which closely resemble cough experiments. The study shows that the criteria employed for assessing the face mask performance must be modified to take into account the penetration dynamics of airborne droplet transmission, the fluid dynamics leakage around the filter, and reduction of efficiency during cough cycles. A new criterion for calculating more accurately the mask efficiency by taking into account the penetration dynamics is proposed. We show that the use of masks will reduce the airborne droplet transmission and will also protect the wearer from the droplets expelled from other subjects. However, many droplets still spread around and away from the cover, cumulatively, during cough cycles. Therefore, the use of a mask does not provide complete protection, and social distancing remains important during a pandemic. The implications of the reduced mask efficiency and respiratory droplet transmission away from the mask are even more critical for healthcare workers. The results of this study provide evidence of droplet transmission prevention by face masks, which can guide their use and further improvement.

280 citations

Journal ArticleDOI
TL;DR: In this article, the transverse jet in supersonic crossflows has been summarized systematically from four aspects, namely single injection, multiport injection, interaction between jet and vortex generator, and interaction between the jet and shock wave.

216 citations