• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.337-339
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• 2008

Abstract: As a shock impinges into a vortex of variable strength, complex shock diffraction can occur. Since a vortex has a fixed rotating direction, the shock wave travelling in one direction creates strong asymmetry in the vortex flow field. The process is that first the shock is divided into two parts by the vortex. One part is moving in the adverse direction opposite to the vortex flow which is captured by the vortex center. The other part is moving in the favorable direction, namely, in the direction same as the vortex flow; it is swung around the vortex, accelerating the vortex flow. In this paper we have investigated numerically using ENO scheme how and why the shock-vortex interaction patterns appear so different for different parametric values. Conclusion is that there are three different types of shock-vortex interaction depending on two related parameters: shock Mach number and vortex Mach number. We present a parameter map by which we can discern what type of interaction pattern appears as a shock impinges into a vortex.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.126-131
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• 2004

The interaction between the hypersonic free stream and the side jet flow at high altitudes is investigated by direct simulation Monte Carlo(DSMC) method. Since there is a great difference in density between the free stream and the side jet flow, the weighting factor technique which could control the number of simulation particles, is applied to calculate these two flows simultaneously. Chemical reactions are not considered in the calculation. For validation, the corner flow passing between a pair of plates that are perpendicularly attached is solved. The side jet flow is then injected into this comer flow and solution is found for the merged flow. Results are compared with the experiments. For a more realistic rocket model, the flow past a blunted cone cylinder shape is solved. The leeward or windward jet injection is merged with this flow. The effect on the rocket surface is observed at various flow angles. The lambda effect and the wake structure are found like low attitudes. High interaction between the free stream and the side jet flow is observed when the side jet is injected in the windward direction.

• Korea-Australia Rheology Journal
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• v.21 no.1
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• pp.39-46
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• 2009

Atherosclerosis is a disease that narrows, thickens, hardens, and restructures a blood vessel due to substantial plaque deposit. The geometric models of the considered stenotic blood flow are three different types of constriction of cross-sectional area of blood vessel; 25%, 50%, and 75% of constriction. The computational model with the fluid-structure interaction is introduced to investigate the wall shear stresses, blood flow field and recirculation zone in the stenotic vessels. The velocity profile in a compliant stenotic artery with various constrictions is subjected to prescribed physiologic waveform. The computational simulations were performed, in which the physiological flow through a compliant axisymmetric stenotic blood vessel was solved using commercial software ADINA 8.4 developed by finite element method. We demonstrated comparisons of the wall shear stress with or without the fluid-structure interaction and their velocity profiles under the physiological flow condition in the compliant stenotic artery. The present results enhance our understanding of the hemodynamic characteristics in a compliant stenotic artery.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.2
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• pp.110-116
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• 2005

This paper deals with interaction between two bubbles or particles and flow around them, visualized by a moving object flow image analyzer(MOFIA) consisting of a three-dimensional (3D) moving object image analyzer(MOIA) and two-dimensional particle image velocimetry(PIV). The experiments were carried out for rising bubbles or particles of various densities, sizes, and/or shapes in stagnant water in a vertical pipe. In the MOFIA employed, 3D-MOIA was used to measure particles or bubbles motion and PIV was used to measure fluid flow, The experimental results showed that the interaction was characterized by the shape, size and density of two particles or bubbles.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.11
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• pp.873-881
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• 2002

The fluid induced vibration (FIV) phenomena of an equivalent airfoil system of MAV have been investigated in low Reynolds number flow region. Unsteady flows with viscosity are computed using two-dimensional incompressible Navier-Stokes equations. The present fluid/structure interaction analysis is based on one of the most accurate computational approach with computational fluid dynamics (CFD) and computational structural dynamics (CSD) techniques. The highly nonlinear fluid/structure interaction phenomena due to severe flow separations have been analyzed for the low Reynolds region that has a dominancy of flow viscosity. The effects of Reynolds number and initial angle of attack on the fluid/structure coupled vibration instability are shown and the qualitative trend of FIV phenomenon is investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.239-243
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• 2012

This paper is concerned with turbulent flow computations using Large Eddy Simulation (LES) and the flow interaction of vortex shedding in a cylindrical duct flow driven by mass blowing through the wall. The purpose is to analyze non-linear combustion characteristics in the presence of vortex shedding generated in a hybrid rocket motor. Experimental studies have shown sudden changes in pressure (referred as a DC-shift), which depend on the strength of vortex strength of incoming flow. The combustion instability because of a sudden change in pressure fluctuations is mainly related with the interaction between vortex shedding. Therefore LES computation on a duct with injected normal blowing was performed to simulate the turbulent flow interactions with the behaviors of vortices and vortex structures along the injected wall.

• Journal of computational fluids engineering
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• v.5 no.2
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• pp.38-46
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• 2000

It has been indicated that the rotor/stator interaction has distinct causes of unsteadiness, such as the viscous vortex shedding, wake/stator interaction and potential rotor/stator interaction. In this paper, the mechanism of unsteady potential interaction in one stage axial compressor is numerically investigated for blade row ratio 1:1 and 2:3 at design point and for blade row ratio 2:3 at off-design point in two-dimensional view point. The numerical technique used is the upwind scheme of Van-Leer's Flux Vector Splitting(FVS) and Cubic spline interpolation is applied on zonal interface. In this study the flow unsteadiness due to potential interaction are found to be larger in blade row ratio 2:3 than in 1:1. The total pressure rise in blade row ratio 2:3 is closer to the real value in design point than that in 1:1. The change of unsteady pressure amplitude according to the variation of stator exit pressure is very small.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.57-70
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• 2008

A high-order accurate Euler flow solver based on a discontinuous Galerkin finite-element method has been developed for the numerical simulations of blade-vortex interaction phenomena on unstructured meshes. A free vortex in freestream was investigated to assess the vortex-preserving property and the accuracy of the present flow solver. Blade-vortex interaction problems in subsonic and transonic freestreams were simulated by adopting a multi-level solution-adaptive dynamic mesh refinement/coarsening technique. The results were compared with those of other numerical and experimental methods. It was shown that the present discontinuous Galerkin flow solver can preserve the vortex structure for significantly longer vortex convection time and can accurately capture the complex unsteady blade-vortex interaction flows, including generation and propagation of acoustic waves.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.57-70
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• 2008

A high-order accurate Euler flow solver based on a discontinuous Galerkin finite-element method has been developed for the numerical simulations of blade-vortex interaction phenomena on unstructured meshes. A free vortex in freestream was investigated to assess the vortex-preserving property and the accuracy of the present flow solver. Blade-vortex interaction problems in subsonic and transonic freestreams were simulated by adopting a multi-level solution-adaptive dynamic mesh refinement/coarsening technique. The results were compared with those of other numerical and experimental methods. It was shown that the present discontinuous Galerkin flow solver can preserve the vortex structure for significantly longer vortex convection time and can accurately capture the complex unsteady blade-vortex interaction flows, including generation and propagation of acoustic waves.

• Journal of the Korea Society of Computer and Information
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• v.28 no.7
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• pp.145-153
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• 2023

The aim of this study is to examine the relationship between self-regulated learning, NLR(non-learning-related) behavior, interaction and flow on satisfaction in database classes. To achieve this purpose, this study proposed a research model consisting of self-regulated learning, NLR behavior, interaction, flow and satisfaction. A survey was conducted to test the research hypotheses, and a total of 122 online questionnaires were obtained and used for the final statistical analysis. The main findings of the analysis are as follows: First, flow was consistently identified as a key determinant of satisfaction. Second, self-regulated learning was found to have a significant effect on flow. Third, NLR behavior and interaction were found to mediate the relationship between self-regulated learning and flow. This study provides insights into the role of NLR behavior and interaction in promoting flow and offers implications for understanding how to promote flow.