박수형 교수

Three κ-ω turbulence models using linear and nonlinear eddy-viscosity formulations are implemented in an implicit multigrid method. Detailed techniques of implementation are presented and discussed. Freezing and limiting strategies are applied to improve robustness and convergence of the multigrid method. The Wilcox κ-ω, κ-w shear-stress transport, and Wilcox-Durbin+ (WD+) models are first tested for flat-plate flow, and the results are in good agreement with the empirical correlations. Numerica

A two-dimensional preconditioned multigrid Navier-Stokes solver has been developed for all Mach number viscous flows. For the computation of all Mach number flows, a local preconditioning technique with a modified reference velocity was used to extend the Harten-Lax-van Leer-Einfeldt (HLLE+) scheme, which has good characteristics for compressible viscous flows. The developed methods used to compute several representative steady problems. Grid refinement and parametric studies are performed to ve

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Phosphate is a key element affecting plant growth. Therefore, the accurate determination of phosphate concentration in hydroponic nutrient solutions is essential for providing a balanced set of nutrients to plants within a suitable range. This study aimed to develop a data fusion approach for determining phosphate concentrations in a paprika nutrient solution. As a conventional multivariate analysis approach using spectral data, partial least squares regression (PLSR) and principal components re

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Dissipation mechanisms of Godunov-type schemes are presented in the framework of unified representation. We first examined the causes of inaccuracy at the contact discontinuity and the dissipation mechanism in the numerical mass flux of the HLLEM scheme. Through a linear perturbation analysis on the oddeven decoupling problem, we discuss necessary conditions for designing a shock stable scheme. The curing methods for each specified problem are also presented. A new improved HLLE(HLLE+) scheme is

Synthetic jet flows from piezoelectric actuators have been investigated for flow control in the field of fluid dynamics. Numerical simulation for a single diaphragm piezoelectric actuator operating in quiescent air is performed to investigate the complex flow field around the slot exit. A periodic velocity transpiration condition is used to simulate the effect of the moving diaphragm. Numerical aspects of the artificial dissipation and time integration schemes are investigated. Results for the f

A technique for the generation of overlapped grid using a simple shooting method, that is a cut-paste algorithm, is presented. It makes possible to generate overlapping grids with moderate mesh interface region. To generate overlapped grids with minimal amount of user inputs, the advancing-front technique using the fringe points as facets is used. To remove hole points initially, fronts using solid bodies and the zones of interference algorithm are used. The overlapped grids are generated for se

Vacuum electrospray deposition (ESD) equipment was designed to prepare polymer thin films. The polymer solution can be injected directly into vacuum system through multi-stage pumping line, so that the solvent residues and ambient contaminants are highly reduced. To test the performance of ESD system, we fabricated organic photovoltaic cells (OPVCs) by injecting polymer solution directly onto the substrate inside a high vacuum chamber. The OPVC fabricated has the structure of Al∕P3HT:PCBM∕PEDOT:

We perform Monte Carlo simulations on stochastic models such as the Wolf-Villain (WV) model and the Family model in a modified version to measure the mean separation l between islands in a submonolayer regime and the damping time t* of layer-by-layer growth oscillations in one dimension. The stochastic models are modified, allowing for diffusion within interval r upon deposition. It is found numerically that the mean separation and the damping time depend on the diffusion interval r, leading to