• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.2
• /
• pp.18-25
• /
• 2007

Computational study on the passive control of the oblique shock-wave/turbulent boundary-layer interaction utilizing slotted plates over a cavity has been carried out. The numerical boundary layer profile upstream of the interaction follows the compressible turbulent boundary-layer theory reasonably well, and the other results also show good agreements with the experimental observations, such as the wall surface pressures and Schlieren flow visualizations. Further, the effects of various slot configuration including number, location and angle of the slots on the characteristics of the interactions, such as the variation of the total pressures, the boundary-layer characteristics downstream of the interaction and the recirculating mass flux through the slots, are also tested and compared.

• Journal of the Society of Naval Architects of Korea
• /
• v.54 no.6
• /
• pp.522-529
• /
• 2017

Air gun shock system is used as an alternative energy source as part of the attempt to overcome the restrictions of economical expense and environmental damage, etc., due to the use of explosives for the UNDerwater EXplosion (UNDEX) shock test. The objectivity of this study is to develop the simulation technique of air gun shock test for the design of model-scale one for the near field non-explosive UNDEX test through its verification with full-scale SERCEL shock test result. Underwater blasting response analysis of full-scale air gun shock test was carried out using highly advanced M&S (Modeling & Simulation) system of FSI (Fluid-Structure Interaction) analysis technique of LS-DYNA code, and was verified by comparing its shock characteristics and behaviors with the results of air gun shock test.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.369-374
• /
• 2010

This paper presents a numerical investigation of the Deflagration to Detonation Transition (DDT) of flame acceleration by a shock wave in combustible gas mixture. A model consisting of the reactive compressible Navier-Stokes equations is used. The effects of viscosity, thermal conduction, species diffusion, and chemical reactions are included. Using this model, the generation of hot spots by repeated shock and flame interaction in front and back of flame and the change of detonation occurrence by various shock intensities (Ms=1.1, 1.2, 1.3) are studied. The simulations show that as the incident shock intensity increases, the Richtmyer-Meshkov (RM) instability becomes stronger and DDT occurrence time is reduced.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.7
• /
• pp.26-31
• /
• 2003

In this paper, supersonic jets impinging on axisymmetric cone were investigated to obtain fundamental design data for jet deflector case of example being VTOL/STOL or rocket launch. It was of interest to study flow phenomena such as shock interactions and separation induced by shear layer. Experiments were conducted to obtain schlieren flow visualization and measurement of surface pressure. Numerical results are compared with the experimental result. The dominant feature of the flow is the shock pattern induced by the interaction between the cone shock and the barrel shock. This pattern can take a wide variety of forms depending on the structure of the free jet and strongly influences the form of the surface pressure distributions.

• Korean Journal of Culture and Social Issue
• /
• v.21 no.1
• /
• pp.45-66
• /
• 2015

This study explored the moderating effects of social supports (family support, home friends support, foreign friends support) and cultural identity (home identity, foreign identity) on the relationships of reverse culture shock and subjective well-being. Participants were 157 returnees who left home-country prior to the age of 19 and resided in the foreign-country for more than three years. The results of hierarchical regression analyses on two-way interaction effect between reverse culture shock and each hypothesized moderator (e.g., family support, home friends support, foreign friends support, home identity, foreign identity) indicated that reverse cultural shock and subjective well-being was negatively related and their relationship was moderated only by family support. Specifically, the relationship between reverse culture shock and subjective well-being was weaker when the level of family support was higher. Subsequently, three-way interaction among reverse culture shock, one of the social support factors, and one of the cultural identity factors was investigated using hierarchical regression analyses. The results showed that the three-way interaction among reverse culture shock, family support, and home identity was significant. The slope difference tests yielded that the relationship between reverse culture shock and subjective well-being was stronger when both levels of family support and home identity were lower compared to when either level of family support or home identity was higher. These results imply that environmental factors such as family support and intrapsychic factor such as home identity might function as a buffer against the negative consequences of reverse culture shock experience.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• v.y2005m4
• /
• pp.386-393
• /
• 2005

The objective of the present study is to develop a new type of the Ballistic range, called 'two-stage light gas gun'. A computational work has been performed to investigate the aerodynamics of a projectile which is launched from the two-stage light gas gun. A moving coordinate method for a multi-domain technique is employed to simulate unsteady projectile flows with a moving boundary. The effect of a virtual mass is added to the axisymmetric unsteady Euler equation systems. The computed results reasonably capture the major flow characteristics which are generated in launching the projectile supersonically, such as the interaction between the shock wave and the blast wave, the interaction between the vortical flow and the barrel shock, and the steady under-expanded jet. The present computational results properly predict the velocity, acceleration, and drag histories of the projectile.

• Journal of computational fluids engineering
• /
• v.13 no.1
• /
• pp.41-48
• /
• 2008

The fluid-structure interaction analysis such as a static aeroelastic analysis requires the result of each analysis as an input to the other analysis. Usually the grids for the fluid analysis and the structural analysis are different, so the results should be transformed properly for each other. The Infinite Plate Spline(IPS) and the Thin Plate Spline(TPS) are used in interpolating the displacement and the pressure. In this study, such interpolation methods are compared with kriging which provides a precise response surface. The static aeroelastic analysis is performed for the supersonic flow field with shock waves and the pressure field is interpolated by the TPS and kriging. The TPS shows tendency to weaken the shock strength, whereas kriging preserves the shock strength.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.10a
• /
• pp.155-160
• /
• 2004

This paper describes a supersonic separation of air-launching rocket from the mother plane. Three dimensional Euler equations were numerically solved to analyze steady/unsteady state fluid flows. To solve the Euler equations, named CFD-FASTRAN that is commercial computation code. The results of simulation clearly demonstrate effect of shock-expansion wave interaction between the rocket and the mother plane. Moreover, important influential factors at separating stage of the rocket were extracted with a comprehensive analysis. Finally, from the consideration of supersonic-separation, a guideline to safety-separation is given to the design of supersonic air-launching rocket.

• 한국전산유체공학회:학술대회논문집
• /
• 2002.10a
• /
• pp.53-63
• /
• 2002

In this numerical approach, strut-placed supersonic annular flow is examined. The geometrical variations of strut cause strong influence on flowfield structures. The geometrical variations are as follows, swept effect, attack angle effect, variation of leading edge shape. These changed features such as velocity structure, pressure structure, shock-boundary layer interaction are compared and analyzed according to each geometrical configuration.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.2 s.257
• /
• pp.109-115
• /
• 2007

Airframe-integrated Scramjet engines of NASA Langley type consist of a compressor, a combustion chamber and a nozzle. When some disturbances occur in one module of the engine, its influences are propagated to other modules. In this study, it is investigated numerically how shock waves were caused by thermal choking in one module propagate upstream and how they influence adjacent modules. The calculations are carried out in 2-dimensional supersonic viscous flow model using explicit TVD scheme in generalized coordinates. The adverse pressure gradient caused by heat addition brings about separation of the wall boundary layers and formation of the oblique shock wave that proceed to upstream. This moving shock wave formed one module blocks the flow coming into the adjacent modules, which makes the modules unstarted.