• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.9
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• pp.615-622
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• 2017

A normal shock wave is initially formed in the shock tube that migrates towards the closed end of the tube, which, in turn, leads to the reflection of shock. Due to the interaction of the reflected shock with the boundary layer, bifurcation of the shock wave takes place. A shock train will be generated after the bifurcated shock wave approaches the contact surface. Until now, only a few studies have been conducted to investigate this shock train phenomenon inside the shock tube. For the present study, a CFD analysis has been performed on a two dimensional axisymmetric model of a shock tube using unsteady, compressible Navier-Stokes equations. In order to investigate the detailed characteristics of the shock train phenomenon, quantitative studies have been performed by varying shock tube length, diameter under fixed diaphragm, and pressure ratio inside a shock tube.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.178-181
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• 2011

Recently, micro shock tube is being extensively used in various fields of engineering applications. The flow characteristics occurring in the micro shock tube may be significantly different from that of conventional macro shock tube due to very low Reynolds number and Knudsen number effects which are, in general, manifested in such flows of rarefied gas, solid-gas two-phase, etc. In these situations, Navier-Stokes equations cannot properly predict the micro shock tube flow. In the present study, a two-dimensional CFD method has been applied to simulate the micro shock tube, with slip velocity and temperature jump boundary conditions. The effects of wall thermal conditions on the unsteady flow in the micro shock tube were also investigated. The unsteady behaviors of shock wave and contact discontinuity were, in detail, analyzed. The results obtained show much more attenuation of shock wave, compared with macro-shock tubes.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.1-6
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• 2008

The performance of shock absorber is directly related to the car behavior and performance, both for handling and comfort. Most of compact car are assembled the passive shock absorber for cost effect but some of compact driver want better performance of shock absorber than standard parts. Therefore, they want the semi-active suspension control system instead of standard damper system. But they only can change the mechanical damping control shock absorber at A/S market. The mechanical damping control shack absorber can not vary the damping force in driving condition so they do not satisfy the mechanical damping control shock absorber system. In this study, electrically damping force controlled shock absorber system is developed based on the mechanical damping force control damper system. This system can vary damping force by switch on dashboard in driving condition. And, this system can satisfy the requirement of tuning market. Therefore, it is expected the system to show the engineering capability of korean damper company and to increase export market share to oversea damper market.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.468-474
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• 2003

1. Schedule for the meetings of ISO/TC108 Mechanical vibration and shock and ISO/TC108/SC3 Use and calibration of shock measuring instruments 2. Minutes for the seventh meeting of ISO/TC108/WG23 Mechanical vibration and shock - Resilient mounting systems - Information for the application of source and receiver isolation (omitted)

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.481-487
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• 2017

The interaction between a shock wave and a boundary layer causes boundary layer separation, shock train, and in some cases, strong unsteadiness in the flow field. Such a situation is also observed in a shock tube, where the reflected shock wave interacts with the unsteady boundary layer. However, only a few studies have been conducted to investigate the shock train phenomenon in a shock tube. In the present study, numerical studies were conducted using the two-dimensional axisymmetric domain of a shock tube, and compressible Navier-Stokes equations were solved to clarify the flow characteristics of shock train phenomenon inside a shock tube. A detailed wave diagram was developed based on the present computational results, which were validated with existing experimental data.

• Korean Journal of Materials Research
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• v.27 no.1
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• pp.25-31
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• 2017

This study investigates changes in the mechanical behaviors, especially hardness and indentation load-displacement curves, of thermal barrier coatings (TBCs) brought about by thermal shock. The TBCs on the Nickel-based bondcoat/superalloy was prepared with diameters of 25.4 mm and $600{\mu}m$ thickness. The results of thermal shock cycling test from $1100^{\circ}C$ of the highest temperature indicate that the thermal shock do not influence on the mechanical behavior, but a continuous decrease in porosity and increase in hardness were observed after 1200 thermal shock cycles; these changes are believed to be due to sintering of thermal barrier coating materials. The results that no degradation in the indentation load-displacement curves indicate that the coating shows good thermal shock resistance up to 1200 cycles at $1100^{\circ}C$ in air.

• Journal of computational fluids engineering
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• v.14 no.3
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• pp.76-85
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• 2009

The shock wave is deformed and the vortex is elongated simultaneously during the shock-vortex interaction. More precisely, the shock wave is deformed to a S-shape, consisting of a leading shock and a lagging shock by which the corresponding local vortex flows are accelerated and decelerated, respectively: the vortex flow swept by the leading shock is locally expanded and the one behind the lagging shock is locally compressed. As the leading shock escapes the vortex in the order of microseconds, the expanded flow region is quickly changed to a compression region due to the implosion effect. An induced shock is developed here and propagated against the vortex flow. This happens for a strong vortex because the tangential flow velocity of the vortex core is high enough to make the induced-shock wave speed supersonic relative to the vortex flow. For a weak shock, the vortex is basically subsonic and the induced shock wave is absent. For a vortex of intermediate strength, an induced shock wave is developed in the supersonic region but dissipated prematurely in the subsonic region. We have expounded these three shock-vortex interaction patterns that depend on the vortex flow regime using a third-order ENO method and numerical shadowgraphs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1319-1324
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• 2002

A theoretical model on shock-vortex interaction is investigated using a numerical technique to solve Navier-Stokes equations. The shock-vortex interaction generated by this model based on the classical Rankin vortex is precisely investigated for a benchmark problem: Dosanjh and Weeks experiment. In terms of shock dynamics, the interaction is categorized to three stages: shock distortion, shock split, and shock-shock interaction. The quadrupolar structure of the sound source produced by the interaction is far supported with the present model, and the difference between experiment and theoretical model is also discussed in this paper.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.337-339
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• 2008

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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• 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.