• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.5
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• pp.41-47
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• 2009

Numerical computations were carried out to analyze the effect of a sub-cavity at several inlet Mach numbers on the control of cavity-induced pressure oscillations in two-dimensional supersonic flow. The present passive control method, the sub-cavity applied to the front wall of a square cavity, was studied for the inlet Mach numbers of 1.50, 1.83 and 2.50. The results show that the sub-cavity is effective in reducing the oscillations, and a resultant amount of the reduction depended on the inlet Mach number, the length of flat plate, and the depth of sub-cavity used as an oscillation suppressor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.119-122
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• 2009

Numerical computations were carried out to analyze the effect of inlet Mach number and sub-cavity on the control of cavity-induced pressure oscillations in two-dimensional supersonic flow. A passive control method wherein a sub-cavity was introduced on the front wall of a square cavity was studied for Mach numbers 1.50, 1.83 and 2.50. The results showed that sub-cavity is effective in reducing the oscillations at different inlet Mach numbers. The resultant amount of attenuation of pressure oscillations depended on the inlet Mach number, length of the flat plate, and the depth of the sub-cavity used as an oscillation suppressor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.453-454
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• 2008

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.23-26
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• 2004

A computational analysis has been conducted to investigate the detailed flow structure inside a supersonic cavity. The free stream Mach number and Reynolds number are 1.83 and $6.02\times10^5$ respectively. In the present study, the depth and width of the cavity are changed to investigate the effect of the cavity dimensions. A fully implicit finite volume scheme is applied to solve the three-dimensional, steady, unsteady, compressible, Navier-Stokes equations. The computed results are validated with the previous experimental data available. The present computation provides reasonable predictions of the cavity flow, compared with experimental results. The obtained results show that a shock wave is generated in front of the downstream edge of the cavity and the dominant frequencies of the pressure oscillations inside the cavity were obtained.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.117-120
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• 2005

The present study describes unsteady flow phenomena generated in a supersonic flow passing over a rectangular cavity and suggests a way of control of pressure oscillation, doing harm to overall performance and stable operation of aerodynamic and industrial applications. The three-dimensional, unsteady, compressible Navier-stokes equations are numerically solved based on a fully implicit finite volume scheme and large eddy simulation. The cavity flow are simulated with and without control methods, including a triangular bump and blowing jet installed near the leading edge of the cavity. The results show that the pressure oscillation is attenuated by both control techniques, especially near the trailing edge of cavity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.586-589
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• 2009

Scramjet engine combustor was tested with "RAMSYS" blow down wind tunnel in Kakuda Space Center, JAXA. As a result, installation of a cavity showed larger combustion pressure than the case without a cavity. Zigzag cavity applied for the first time in this experiment, showed the largest combustion pressure and is expected to contribute to the stable and economic operation of scramjet.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.3
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• pp.27-33
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• 2009

A computational study has been performed out to evaluate the effect of a vertical porous barrier on the pressure oscillations in a supersonic cavity. The porous barriers with different perforations were vertically installed into a rectangular cavity at Mach numbers 1.50, 1.83 and 2.50. TVD finite difference MUSCL scheme was employed to solve the two-dimensional, unsteady, compressible Navier-Stokes equations. The present vertical porous barrier considerably altered the characteristics of the time-dependent shear layers that occur at the upstream edge of cavity and remarkably reduced the pressure oscillations inside the supersonic cavity. The present results showed that the effectiveness of passive control using the present porous vertical barrier is dependent on Mach number and the perforation of the porous barrier.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.235-238
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• 2005

The unsteady supersonic flow over two- and three-Dimensional cavities has been analyzed by the integration of unsteady Reynolds-Averaged Navier-Stokes(RANS) with the k - w turbulence model. The unsteady flow is characterized by the periodicity due to the mutual relation between the shear layer and the internal flow in cavities. Numerical method is upwind TVD scheme based on the flux vector split with the Van Leer limiters, and time accuracy is used explicit 4th stage Runge-Kutta scheme. Cavity flows are Comparison of two- and three-dimensional. The cavity has a L/D ratio of 3 for two-dimensional case. and same L/D and W/D ratio is 1 for three-dimensional case. The Mach and Reynolds numbers are held constant at 1.5 and 450000 respectively. For the three-dimensional case, the flow field is observed to oscillate in the 'shear layer mode' with a feedback mechanism that follow Rossiter's formula. On the other hand, the self-sustained oscillating flow transitions to a 'wake mode' for the two-dimensional simulation, with more violent fluctuations inside the cavity.

• Journal of computational fluids engineering
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• v.10 no.4 s.31
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• pp.51-58
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• 2005

The unsteady supersonic flow over two- and three-dimensional cavities has been analyzed by the integration of unsteady Reynolds-Averaged Navier-Stokes(RANS) with the k-$\omega$ turbulence model. The unsteady flow is characterized by the periodicity due to the mutual relation between the shear layer and the internal flow in the cavity. An explicit 4th order Runge-Kutta scheme and an upwind TVD scheme based on the flux vector split with the van Leer limiters are used for time and space discritizations, respectively. The cavity has a L/D ratio of 3 for two-dimensional case, and same L/D and W/D ratio of I for three-dimensional case. The Mach and Reynolds numbers are 1.5 and 450000 respectively. In the three-dimensional flow, the field is observed to oscillate in the 'shear layer mode' with a feedback mechanism that follows Rossiter's formula. In the two-dimensional simulation, the self-sustained oscillating flow has more violent fluctuation inside the cavity. The primary fluctuating frequencies of two- and three- dimensional flow agree very well with the 2nd mode of Rossiter's frequency. In the three-dimensional flow, the 1st mode of frequency could be seen.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.42-47
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• 2004

Air-fuel mixing and flame-holding are two important factors that have to be considered in the design of an injection system. Different injection strategies have been proposed with particular concern for rapid air-fuel mixing and flame-holding. Two representative injection techniques can be applied in a supersonic combustor. One of the simplest approaches is a transverse(normal) injection. The cavity flame holder, an integrated fuel injection/flame-holding approach, has been proposed as a new concept for flame holding and air-fuel mixing in a supersonic combustor. This paper describes numerical efforts to characterize the flame-holding and air-fuel mixing process of a model scramjet engine combustor, where hydrogen is injected into a supersonic cross flow and a cavity. The combustion phenomena in a model scramjet engine, which has been experimentally studied at University of Queensland and Australian National University using a free-piston shock tunnel, were observed around the separation region of the transverse injector upstream and the inside cavity. The results show that this flow separation generates recirculation regions which increase air-fuel mixing. Self-ignition occurs in the separation-freestream and cavity-fteestream interfaces.