• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.921-926
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• 2005

In the idealized model problem of the interaction between a planar travelling shock and a symmetric vortex, the physics of shock distortion and quadrupole sound generation are well known to many researchers. However, the authors have distinguished the weak waves reflected and transmitted by the complicated photograph images obtained from a shock tube experiment. In this paper, we introduces a parametric study based on Navier-Stokes simulation and Rankin vortex model to see the difference of shock deformation shapes. Four combination of the strength of shock and vortex are respectively selected from a parameter plane of shock and vortex strength extended to the strong vortex region. The result shows clearly discernable wave morphology for the main parameters, which is not yet explicitly mentioned by other researchers.

• Structural Engineering and Mechanics
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• v.16 no.5
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• pp.519-531
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• 2003

Piezoelectric actuators have long been recognised for use in aerospace structures for control of structural shape. This paper looks at active control of the swept shock wave/turbulent boundary layer interaction using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a plenum chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, reducing wave drag. Active control allows optimum control of the interaction, as it would be capable of positioning the control region around the original shock position and unimorph tip deflection, hence mass transfer rates. The actuators are modelled using classical composite material mechanics theory, as well as a finite element-modelling program (ANSYS 5.7).

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.23-28
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• 1999

In this paper we study numerically the shock-vortex interaction in the shear layer generated by moving shock waves above and below a flat plate. The faster normal shock is diffracted at the tip of the flat plate, producing a starting vortex. The slower normal shock below the flat plate arrives soon later to run across the vortex and make interaction. The two shocks are merged together and reflected back at the closed end of the shock tube to impinge on the shear layer developing multiple vortexlets. The computational simulation based on Euler and Navier-Stokes equations shows good prediction.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.29-34
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• 1999

A two-dimensional Navier-Stokes code based on AUSMPW+ scheme has been developed to simulate the hypersonic flowfield of hypersonic shock-shock interaction. AUSMPW+ scheme is a new hybrid flux splitting scheme, which is improved by introducing pressure-based weight functions to eliminate the typical drawbacks of AUSM-type schemes, such as non-monotone pressure solutions. To study the real gas effects, three different gas models are taken into account in this paper: perfect gas, equilibrium flow and nonequilibrium flow. It has been investigated how each gas model influences on the peak surface loading, such as wall pressure and wall heat transfer, and unsteady flowfield structure in the region of shock-shock interaction. With the results, the value of peak pressure is not sensitive to the real gas effects nor to the wall catalyticity. However, the value of peak heat transfer rates is affected by the real gas effects and the wall catalyticity. The structure of the flowfield also changes drastically in the presence of real gas effects.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.316-328
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• 1997

There were appreciable progresses on the study of shock wave / boundary layer interaction control in the transonic flow without nonequilibrium condensation. But in general, the actual flows associated with those of the airfoil of high speed flight body, the cascade of steam turbine and so on accompany the nonequilibrium condensation, and under a certain circumstance condensation shock wave occurs. Condensation shock wave / boundary layer interaction control is quite different from that of case without condensation, because the droplets generated by the result of nonequilibrium condensation may clog the holes of the porous wall for passive control and the flow interaction mechanism between the droplets and the porous system is concerned in the flow with nonequilibrium condensation. In these connections, it is necessary to study the condensation shock wave / boundary layer interaction control by passive cavity in the flow accompanying nonequilibrium condensation with condensation shock wave. In the present study, experiments were made on a roof mounted half circular arc in an indraft type supersonic wind tunnel to evaluate the effects of the porosity, the porous wall area and the depth of cavity on the pressure distribution around condensation shock wave. It was found that the porosity of 12% which was larger than the case of without nonequilibrium condensation produced the largest reduction of pressure fluctuations in the vicinity of condensation shock wave. The results also showed that wider porous area, deeper cavity for the same porosity of 12% are more favourable "passive" effect than the cases of its opposite. opposite.

• Journal of Mechanical Science and Technology
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• v.15 no.3
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• pp.366-373
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• 2001

A numerical analysis of shock wave/boundary layer interaction in transonic/supersonic axial flow compressor cascade has been performed by using a characteristics upwind Navier-Stokes method with various turbulence models. Two equation turbulence models were applied to transonic/supersonic flows over a NACA 0012 airfoil. The results are superion to those from an algebraic turbulence model. High order TVD schemes predicted shock wave/boundary layer interactions reasonably well. However, the prediction of SWBLI depends more on turbulence models than high order schemes. In a supersonic axial flow cascade at M=1.59 and exit/inlet static pressure ratio of 2.21, k-$\omega$ and Shear Stress Transport (SST) models were numerically stables. However, the k-$\omega$ model predicted thicker shock waves in the flow passage. Losses due to shock/shock and shock/boundary layer interactions in transonic/supersonic compressor flowfields can be higher losses than viscous losses due to flow separation and viscous dissipation.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.79-84
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• 1999

The shock wave diffracted behind a finite wedge is partially scattered after interacting with a starting vortex originated from the sharp vertex of the wedge. The shock is divided into the accelerated and decelerated shocks. The decelerated shock then interacts with the small vortexlets brought about by the vortex instability, producing weak compression waves. The shock-shock interaction produces Mach stems. Through this successive process, the shock attenuated. In this study, these complicated shock phenomena are computed using Euler equations and compared with experimental results obtained by the authors.

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1311-1318
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• 2002

An experimental model is investigated in this paper using the experimental method with a shock tube and the numerical technique. The shock-vortex interaction generated by this model is visualized with various methods: holographic interferometry, shodowgraphy, and numerical computation. In terms of shock dynamics, there are two meaningful physics in the present problem. They are reflective wave from the slip layer at the vortex edge and transmitted shock penetrating the vortex core. The discussion in this study is mainly focused on the two kinds of waves contributing to the quadrupolar pressure distribution around the vortex center during the interaction.

• Journal of the Korean Society of Visualization
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• v.13 no.3
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• pp.29-34
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• 2015

The interaction between a normal shock wave and a boundary layer along a wall surface in internal compressible flows causes a very complicated flow. This interaction region containing shock train and mixing region is called as pseudo-shock waves. Pseudo-shock waves in the divergent part of a rectangular nozzle have been investigated by using large-eddy simulation (LES). LES studies have been done for the complex flow phenomena of three-dimensional pseudo-shock waves. The LES results have been validated against experimental wall-pressure measurements. The LES results are in good agreement with experimental results. Pseudo-shock length and corner separation have been studied in three-dimensional LES model. Comparison of centerline pressure measurement and 3D visualization measurement has been discussed for the corner separation position. It has been concluded that the pseudo-shock length should be measured by using 3D visualization measurement.