• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.637-644
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• 2005

This paper describes the numerical simulation of the interaction between longitudinal vortices ("common flow up") and a 3-D turbulent boundary layer over a flat plate To analyze the common flow up Produced from vortex generators. the flow field behind the vortex generators Is modeled by the information that is available from studies on a half-delta winglet. Also. the Reynolds-averaged Navier-Stokes equation for three-dimensional turbulent flows. together with a two-layer turbulence model to resolve the near-wall flow, is solved by the method of AF-ADI. The computational results predict that the boundary layer is thinned in the regions where the secondary flow is directed toward the wall and thickened where it is directed away from the wall Also. the numerical results. such as Reynolds stresses. turbulent kinetic energy and skin friction characteristics generated from the vortex generators . are reasonably close to the experimental data.

• Wind and Structures
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• v.23 no.2
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• pp.109-125
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• 2016

Flow interference is investigated between two tripped cylinders of identical diameter D at stagger angle ${\alpha}=0^{\circ}{\sim}180^{\circ}$ and gap spacing ratio $P^*$ (= P/D) = 0.1 ~ 5, where ${\alpha}$ is the angle between the freestream velocity and the line connecting the cylinder centers, and P is the gap width between the cylinders. Two tripwires, each of diameter 0.1D, were attached on each cylinder at azimuthal angle ${\beta}={\pm}30^{\circ}$, respectively. Time-mean drag coefficient ($C_D$) and fluctuating drag ($C_{Df}$) and lift ($C_{Lf}$) coefficients on the two tripped cylinders were measured and compared with those on plain cylinders. We also conducted surface pressure measurements to assimilate the fluid dynamics around the cylinders. $C_D$, $C_{Df}$ and $C_{Lf}$ all for the plain cylinders are strong function of ${\alpha}$ and $P^*$ due to strong mutual interference between the cylinders, connected to six interactions (Alam and Meyer 2011), namely boundary layer and cylinder, shear-layer/wake and cylinder, shear layer and shear layer, vortex and cylinder, vortex and shear layer, and vortex and vortex interactions. $C_D$, $C_{Df}$ and $C_{Lf}$ are very large for vortex and cylinder, vortex and shear layer, and vortex and vortex interactions, i.e., the interactions where vortex is involved. On the other hand, the interference as well as the strong interactions involving vortices is suppressed for the tripped cylinders, resulting in insignificant variations in $C_D$, $C_{Df}$ and $C_{Lf}$ with ${\alpha}$ and $P^*$. In most of the (${\alpha}$, $P^*$ ) region, the suppressions in $C_D$, $C_{Df}$ and $C_{Lf}$ are about 58%, 65% and 85%, respectively, with maximum suppressions 60%, 80% and 90%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.3
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• pp.375-383
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• 2002

The flowfield of transverse jet in a supersonic air stream subjected to shock wave turbulent boundary layer interactions is simulated numerically by Generalized Taylor Galerkin(GTG) finite element methods. Effects of turbulence are taken into account with a two-equation (k-$\varepsilon$) model with a compressibility correction. Injection pressures and slot widths are varied in the present study. Pressure, separation extents, and penetration heights are compared with experimental data. Favorable comparisons with experimental measurements are demonstrated.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.70.5-70.5
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• 2008

• Journal of the Korean Society of Combustion
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• v.18 no.3
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• pp.31-37
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• 2013

Numerical simulations are conducted to investigate the feature of spontaneous ignition of hydrogen within a certain length of downstream tube released by the failure of pressure boundaries of various geometric assumption. The results show that the ignition feature can be varied with the shape of pressure boundary. The ignition at the contact region are developed at the spherical pressure boundaries due to multi-dimensional shock interactions, whereas the local ignition is developed in limited area such as boundary layer at the planar pressure boundary conditions. The spontaneous ignition inside the tube can be generated from the reaction region of only boundary layer regardless of existence of the reaction of core region.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.306-309
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• 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 Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.327-330
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• 2006

Numerical study on the passive control of the oblique shock wave/turbulent boundary-layer interaction control utilizing slotted plates over a cavity has been carried out. Numerical results have been compared with the experimental observations, such as pitot/wall surface pressures and Schlieren flow visualizations, obtained for the same boundary conditions. It was found that the present numerical results shows a good agreement with experimental data. Further, the effect of different slot configurations including various number, location and angle of slots on the characteristics of the interactions are also tested, focusing on the variation of the piot pressure and the boundary-layer characteristics downstream of the interaction and the recirculating mass flux through cavity.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.25-32
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• 2001

A passive control method of the interaction between a weak normal shock-wave and a turbulent boundary-layer was simulated using two-dimensional Navier-Stokes computations. The inflow Mach number just upstream of the normal shock wave was 1.33. A porous plate wall having a cavity underneath was used to control the shock-wave/turbulent boundary-layer interaction. The flows through the porous holes and inside the cavity were investigated to get a better understanding of the flow physics involved in this kind of passive control method. The present computations were validated by some recent wind tunnel tests. The results showed that downstream of the rear leg of the $\lambda$-shock wave the main stream inflows into the cavity, but upstream of the rear leg of the $\lambda$-shock wave the flow proceeds from the cavity toward to the main stream. The flow through the porous holes did not choke fur the present shock/boundary layer interaction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.11
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• pp.747-754
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• 2022

An experimental study was carried out to control a shock-induced boundary layer separation by utilizing the supersonic sweeping jet from the fluidic oscillator. High-speed schlieren, surface flow visualization, wall pressure measurement and precise Pitot tube measurement were applied to observe the influences of the location and the supply pressure of the fluidic oscillator on the characteristics of the oblique-shock-induced boundary layer separation. The characteristics of the separation control by the present supersonic fluidic oscillator was quantitatively analyzed by comparing with a conventional control method utilizing an air-jet vortex generator.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1730-1735
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• 2003

The plume-induced shock wave is a complex phenomenon, consisting of plume-induced boundary layer separation, separated shear layer, multiple shock waves, and their interactions. The knowledge base of plume interference effect on powered missiles and flight vehicles is not yet adequate to get an overall insight of the flow physics. Computational studies are performed to better understand the flow physics of the plume-induced shock and separation particularly at high plume to exit pressure ratio. Test model configurations are a simplified missile model and two rounded and porous afterbodies to simulate moderately and highly underexpanded exhaust plumes at the transonic/supersonic speeds. The result shows that the rounded afterbody and porous wall attached at the missile base can alleviate the plume-induced shock wave phenomenon, and improve the control of the missile body.