Sejong Oh

Numerical Studies of Supersonic Planar Mixing and Turbulent Combustion using a Detached Eddy Simulation (DES) Model

We present a simulation of a hybrid Reynolds-averaged Navier Stokes / Large Eddy Simulation (RANS/LES) based on detached eddy simulation (DES) for a Burrows and Kurkov supersonic planar mixing experiment. The preliminary simulation results are checked in order to validate the numerical computing capability of the current code. Mesh refinement studies are performed to identify the minimum grid size required to accurately capture the flow physics. A detailed investigation of the turbulence/chemistry interaction is carried out for a nine species 19-step hydrogen-air reaction mechanism. In contrast to the instantaneous value, the simulated time-averaged result inside the reactive shear layer underpredicts the maximum rise in H₂O concentration and total temperature relative to the experimental data. The reason for the discrepancy is described in detail. Combustion parameters such as OH mass fraction, flame index, scalar dissipation rate, and mixture fraction are analyzed in order to study the flame structure.

Correction of Roe's Approximate Riemann Solver for Non-Ideal Gas Equation of State

For the analysis of compressible flow with real gas effect, characteristic form of Roes Riemann solver was derived again using real gas equation of state and variable specific heat, and it was extended to multi component reactive system. From this study, it is known that some correction should be made for the use of existing numerical algorithm. 1) Sonic speed and characteristic variable should be corrected with real gas effect. 2) Roes average was applicable only with the assumption of constant properties. 3) Artificial damping term and characteristic variables should be corrected but their influence may not be significant.

Ice Accretion on Helicopter Fuselage Considering Rotor-Wake Effects

To accurately predict the ice shape on the fuselage under rotor-wake effects, discrete modeling of individual tip vortices is essential to determine the local aerodynamic interactions between the vortex and the fuselage. To this end, the actuator surface model is developed and applied to the present study. Then, water-droplet-trajectory prediction, thermal analysis, and ice growth module are seamlessly integrated. This study aims to perform detailed analysis of the rotor downwash effects on ice that accretes on a helicopter fuselage and to determine the variation with respect to the forward flight speed. As a result of comprehensive numerical computations, the following conclusions are reached. First, the rotor inflow transforms the droplet trajectories, the location of ice accretion and the amount of ice are changed. Actually, 16.5% less ice is accumulated on the overall fuselage in the rotor–fuselage interaction case compared to the isolated fuselage case. Second, a clear-cut distinction of the icing lo...

Prediction of Glaze Ice Accretion on 2D Airfoil

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Quasi-steady State Simulation of Rotating Detonation Engine

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A Preliminary Design of Flight Test Conditions for a Sub-scale RBCC Engine using a Sounding Rocket

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Analysis of Relations between Ice Accretion Shapes and Ambient Conditions by Employing Self-Organization Maps and Analysis of Variance

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Part1 : Numerical Code Validation and Quantitative Analyses of Ice Accretion around Airfoils

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New Technologies of Space Launch Vehicles including Electric-Pump Cycle Engine

We performed a numerical simulation based on the two-dimensional (2-D) unsteady Euler’s equation with a single-step Arrhenius reaction model in order to investigate the detonation wave front propagation of an Argon (Ar) diluted oxy-hydrogen mixture (2H₂ + O₂ + 12Ar). This simulation operates in the detonation frame of reference. We examine the effect of grid size and the performance impact of integrated quantities such as mass flow. For a given set of baseline conditions, the minimal and maximum grid resolutions required to simulate the respective detonation waves and the detonation cell structures are determined. Tertiary shock wave behavior for various grids and pre-exponential factors are analyzed. We found that particle fluctuation can be weakened by controlling the mass flow going through the oblique shock waves.

Improved actuator surface method for wind turbine application

Various R&D programs for rocket-based combined cycle (RBCC) engines have progressed worldwide for the space development and the defense applications. As a way toward indigenous domestic RBCC program, a preliminary design of flight test conditions was studied in this study for a sub-scale RBCC engine using a sounding rocket. Launch and flight profiles were calculated for several booster options and compared with that of HyShot II program. The result shows that the Korea Sounding Rocket-II (KSR-II) is a proper candidate to perform the flight test available in Korea. The recommend flight test conditions with KSR-II are Mach 6.0 with a test vehicle of 230 kg and Mach 7.4 with 50 kg. Present study will soon be followed by a design of sub-scale RBCC for a flight test using a sounding rocket.