• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.7
• /
• pp.32-40
• /
• 2003

An experimental research has been carried out for flow visualizations of the shock wave/turbulent boundary-layer interaction control utilizing the aeroelastic flaps, Spark shadowgraphs, kerosene-lampblack tracings for the surface streakline pattern, and interference fringe patterns over a thin oil-film applied at the downstream of the shock interactions have been obtained , Effects of variation of the shapes and thicknesses of the flaps are tested, and all the results are compared to the solid-wall reference case without flow-control mechanism , From the qualitative observation of the variation of skin friction utilizing the interference fringe patterns over the silicone oil-film, a strong spanwise variation of the skin friction with a narrow and long region of separation has been noticed near the centerline behind the shock structure, which phenomenon demonstrate a strong three-dimensionality of the shock interaction flows, Influence of the shape of the cavity under the flaps to the shock interaction is also tested, and it is observed that the shape of the cavity is not negligible.

• International Journal of Fluid Machinery and Systems
• /
• v.1 no.1
• /
• pp.24-32
• /
• 2008

Bleeding away a part of the boundary layer next to the wall is an effective method for controlling boundary-layer distortions from incident shock waves or curvature in geometry. When the boundary-layer flow is supersonic, the physics of bleeding with and without an incident shock wave is more complicated than just the removal of lower momentum fluid next to the wall. This paper reviews CFD studies of shock-wave/boundary-layer interactions on a flat plate with bleed into a plenum through a single hole, three holes in tandem, and four rows of staggered holes in which the simulation resolves not just the flow above the plate, but also the flow through each bleed hole and the plenum. The focus is on understanding the nature of the bleed process.

• Journal of the Korean Society of Visualization
• /
• v.8 no.3
• /
• pp.56-62
• /
• 2010

The interaction patterns between shock wave and boundary layer in a rocket nozzle are mainly classified into two categories, FSS(Free Shock Separation) and RSS(Restricted Shock Separation), both of which are associated with the thrust characteristics as well as side loads of the engine. According to the previous investigations, strong side loads of the engine are produced during the period of transition from FSS to RSS or vice versa. The present work aims at investigating the unsteady behavior of the separation shock waves in a two-dimensional supersonic nozzle, using experimental method and CFD. Schlieren optical method was employed to visualize the time-mean and time-dependent shock motions in the nozzle. The unsteady, compressible N-S equations with SST K-$\omega$ turbulence closure were solved using a fully implicit finite volume scheme. The results obtained show the separation shock motions during the transition of the interaction pattern.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.161-164
• /
• 2002

In the present study, a passive control method, using the porous wall and cavity system, is applied to the shock wave/boundary layer interactions in transonic moist air flow. The two-dimensional, unsteady, compressible Navier-Stokes equations, which are fully coupled with a droplet growth equation, are solved by the third-order MUSCL type TVD finite difference scheme. Baldwind-Lomax turbulence model is employed to close the governing equations. In order to investigate the effectiveness of the present control method, the total pressure losses of the flow and the time-dependent behaviour of shock motions are analyzed in detail. The computed results show that the present passive control method considerably reduces the total pressure losses due to the shock/boundary layer interaction in transonic moist air flow and suppresses the unsteady shock wave motions over the airfoil, as well. It is also found that the location of the porous ventilation significantly influences the control effectiveness.

• 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.

• Journal of computational fluids engineering
• /
• v.2 no.2
• /
• pp.59-72
• /
• 1997

A numerical model is constructed to simulate the interactions of oblique shock wave / turbulent boundary layer on a strongly heated wall. The heated wall temperature is two times higher than the adiabatic wall temperature and the shock wave is strong enough to induce boundary layer separation. The numerical diffusion in the finite volume method is reduced by the use of a higher order convection scheme(UMIST scheme) which is a TVD version of QUICK scheme. The turbulence model is Chen-Kim two time scale model. The comparison of the wall pressure distribution with the experimental data ensures the validity of this numerical model. The effect of strong wall heating enlarges the separation region upstream and downstream. In order to eliminate the separation, wall suction is applied at the shock foot position. The bleeding slot width is about same as the upstream boundary layer thickness and suction mass flow is 10% of the flow rate in the upstream boundary layer. The final configuration of the shock reflection pattern and the wall pressure distribution approach to the non-viscous value when wall suction is applied.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.2
• /
• pp.329-340
• /
• 1997

A passive control of interaction of condensation shock wave / boundary layer for reducing the strength of condensation shock was conducted experimentally in a 2.5 * 8 cm$^{2}$ indraft type supersonic wind tunnel. The effects of following factors on passive control were investigated: 1) the thickness of porous wall, 2) the diameter of porous hole, and 3) the orientation of porous hole. On the other hand, the location of nonequilibrium condensation region and condensation shock wave was controlled by regulation of the stagnation conditions. Surface static pressure measurements as well as Schlieren observations of the flow field were obtained, and their effects were compared with the results the cases of without passive control. It was found that thinner porous wall, smaller porous hole and FFH orientation for the same cavity size and porosity of 12% are more favourable than the cases of its opposite.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.05a
• /
• pp.306-309
• /
• 2006

Passive control of the shock wave/turbulent boundary-layer interaction control utilizing slotted plates over a cavity has been carried out. Effect of various slot configurations on the characteristics of the interactions are tested. Pitot/wall surface pressure distributions and flow visualizations including Schlierens and interference fringe patterns over a thin oil-film have been obtained at the downstream of the shock interactions. It was found that the interaction control by a certain slot-configuration could lead a reduction of the total pressure loss through the shock wave, however, the boundary layer thickness became thicker as compared with the case of no control.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.159-160
• /
• 2002

New S-shaped aeroelastic mesoflaps are utilized to control normal shock/boundary-layer interactions. New generation of the mesoflaps is designed f3r a better rigidness and a good flow uniformity across the ulteractions. ,Major advantages of the mesoflap system can be a better total pressure recovery downstream of the interactions due to the lambda shock structure over the flap system, and a rehabilitation of the thickened boundary layer due to bleeding through a cavity underneath the flap system. Skin friction has been measured downstream of the interactions, using the laser interferometer skin friction (LISF) meter, which optically detects the rate of thinning of an oil film applied to the test surface. Various flap-thicknesses of the S-shaped mesoflap arrays are tested, and the results are compared to the solid-wall reference case. Overall, not much difference in the level of skin friction is noticed for the S-shaped flap arrays of various thicknesses, and its level is lower than the skin friction downstream of the solid-wall interaction

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.336-340
• /
• 2017

When supersonic flow is through an internal duct, there forms a flow structure called pseudo-shock. Pseudo-shock is a result of shockwave-boundary layer interaction(SBLI) and to simulate pseudo-shock correctly, one needs to correctly anticipate not only the strength of the shock but also the boundary layer behavior as well. In this study, pseud-shockwave structure at a rectangular duct will be numerically simulated using dedicated inlet boundary conditions to obtain accurate solution in terms of its structure and pressure rise pattern.