• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.662-665
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• 2011

Pintle technology, which is one of the thrust control method for solid rocket motor, can control the thrust by the control of nozzle throat area through the pintle moving. For studying the unsteady flow characteristics of pintle nozzle by needle type pintle moving, cold flow test and numerical analysis were performed. The pressure distribution on the pintle tip was varied for pintle moving and stopping and thrust was varied by this effects.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.6
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• pp.474-482
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• 2007

An analysis is made for flow and rocket motion during a supersonic separation stage of an air-launching rocket(ALR) from the mother plane. Three-dimensional compressible Navier-Stokes equations are numerically solved to analyze the steady/unsteady flow fields around the rocket which is being separated from the mother plane configuration(F-4E Phantom). Simulation results clearly demonstrate the effect of shock-expansion wave interaction around both of the rocket and the mother plane. To predict the behavior of the ALR by the change of the center-of-gravity, three cases of numerical analysis are performed. As a result, a design-guideline of supersonic air-launching rockets for safe separation is proposed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.173-179
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• 2012

Steady and unsteady three-dimensional RANS simulations have been performed on partial admission supersonic axial turbine having backward/forward sweep angles(${\pm}15^{\circ}$) and the results are compared with each other. The objective of this paper is to study the effect of unsteadiness on turbine flow characteristics and performances. The all results indicated that the losses of unsteady simulations were greater than those of steady cases. It was also shown that BSW model give the effect on the reducing of mass flow rates of tip leakage. In unsteady simulation, the increase of t-to-s efficiency at Rotor Out plane was observed more clearly.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.8
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• pp.18-25
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• 2005

This paper describes a supersonic separation of air-launching rocket from the mother plane. Three dimensional Euler equations were numerically solved to analyze steady/unsteady state fluid flows. The results of simulation clearly demonstrate effect of shock-expansion wave interaction between the rocket and the mother plane. Moreover, important influential factors at separating stage of the rocket were extracted with a comprehensive analysis. Finally, from the consideration of supersonic-separation, a guideline to safety-separation is given to the design of supersonic air-launching rocket.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.79-82
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• 2009

Unsteady numerical analysis of an entire supersonic propulsion system from intake to nozzle was performed to study dynamic interaction between terminal shock in the intake and flame in the combustor. Both acceleration and cruise flight-modes were considered. Acoustic mode of the entire engine for both flight-modes were investigated by detail analysis of pressure fluctuation at each location of engine.

• 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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.1
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• pp.1-9
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• 2017

In this paper, we present and verify an aerodynamic reduced-order model (ROM) based on a quasi-steady flow method to reduce the computational cost of supersonic aeroelastic analysis. For supersonic flows, especially when the characteristic time scale of the flow is small compared to that of the structural motion, the unsteadiness of flow can be negligible, and quasi-steady solutions can be used instead of the unsteady solutions for the aeroelastic analysis. Kriging method is used to build the ROM of the aerodynamics. The surface solutions from the ROM are used as the boundary conditions for the structural analysis at each time-step. The ROM is validated against the unsteady solutions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.41-44
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• 2003

In spite of many researches made on the supersonic jets until now, detailed three-dimensional structures of supersonic jets are not well hewn. In the current study, the detailed structures of three-dimensional supersonic jets are numerically investigated using a CFD method. The total variation diminishing (TVD) scheme is used to solve the unsteady, three-dimensional, compressible Euler equations. Computational results are visualized to investigate the major features of supersonic jets. The three-dimensional computation results show that the structures of the supersonic jets are significantly different from those of the two-dimensional or axisymmetric supersonic jets.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.329-334
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• 2007

An axisymmetric supersonic jet screech in the Mach number range from 1.07 to 1.2 is numerically simulated. The axisymmetric mode is the dominant screech mode for an axisymmetric jet. The Reynolds-averaged Navier-Stokes equations in the conjunction with modified Spalart-Allmaras turbulence model are employed. A high resolution finite volume essentially non-oscillatory(ENO) schemes are used along with nonreflecting characteristic boundary conditions that are crucial to screech tone computations to accurately capture the sound waves, shock-cell structures, unsteady shock motions and large-scale instability waves.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.411-414
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• 2010

In supersonic propulsion system, the inlet buzz phenomenon in the subcritical operation arises large pressure oscillation, combustion instability, and thrust loss, etc. Inlet Buzz phenomenon and the spray injection/combustion are figured out by the unified unsteady numerical analysis. TAB(Taylor Analogy Breakup) model was applied. Acoustic mode of the entire engine was investigated by detail analysis of pressure fluctuation at each location of the engine.