Sung-Ki Jung

An Aerodynamic Shape Optimization Study to Maximize the Range of a Guided Missile

This paper describes a research of a shape optimization study to maximize a range of a guided missile with canards and tailfins. To design a guided missile for the maximum range, a shape optimization system is incorporated with a trajectory analysis and an optimization technique. In the trajectory analysis part, a component build-up method is directly connected to the equation of motion to calculate aerodynamic coefficients at every time step. In the optimization part, real coded adaptive range genetic algorithm was adopted to find out an optimum shape of the global maximum range. The shape optimization system of a guided missile for the maximum range can maximize the range of a guided missile and yield the optimum shape of canards and tailfins. The analysis results confirmed that the optimum shape thus derived extended the range of the base shape by 5.8% for the unguided case and by 21.4% for the guided case.

Development of Eulerian Droplets Impingement Model Using HLLC Riemann Solver and POD-Based Reduced Order Method

A finite volume method based on approximate Riemann solver is proposed as a basic building block for computing the Eulerian droplet impingement model. The HLLC approximate Riemann solver, which is originally developed for shallow water equations of the fluid depth and velocity field, is applied to the Eulerian droplet model. The positivity condition in liquid water contents is achieved through the HLLC solver. Then, a proper orthogonal decomposition method, a reduced order model that optimally captures the energy content from a large multi-dimensional data set, is utilized to efficiently predict the collection efficiency on an airfoil. It is shown that the collection efficiency reconstructed by utilizing four modes of the POD is in very close agreement with the original value.

A Study on Truncated Flapped Airfoil for Efficient Icing Wind Tunnel Test

The evaluation of supercooled water droplet impingement characteristics of full-scale aircraft components in wind tunnels under icing conditions has been severely limited by the relative size of the component and the test facility. The concept of truncated airfoil sections has been suggested in order to extend the operational range of icing tunnels. With proper deflection of the small trailing-edge flap on the truncated airfoil the local pressure distribution may remain very close to that of the full-scale airfoil. In this study the shape of a truncated flapped airfoil is investigated for various deflection angles. To validate the truncated flapped airfoils, air flow and collection efficiency over the truncated airfoil are compared with the results of the full-scale airfoil obtained from the state-of-the-art icing simulation code.

A Study on Real-Coded Adaptive Range Multi-Objective Genetic Algorithm for Airfoil Shape Design

In this study, the real-coded adaptive range multi-objective genetic algorithm code, which represents the global multi-objective optimization algorithm, was developed for an airfoil shape design. In order to achieve the better aerodynamic characteristics than reference airfoil at landing and cruise conditions, maximum lift coefficient and lift-to-drag ratio were chosen as object functions. Futhermore, the PARSEC method reflecting geometrical properties of airfoil was adopted to generate airfoil shapes. Finally, two airfoils, which show better aerodynamic characteristics than a reference airfoil, were chosen. As a result, maximum lift coefficient and lift-to-drag ratio were increased of 4.89% and 5.38% for first candidate airfoil and 7.13% and 4.33% for second candidate airfoil.

Eulerian-based Numerical Modeling for Impingement Prediction of Supercooled Large Droplets

Supercooled large droplet issues in aircraft icing have been continually reported due to the important safety considerations. In order to simulate the impingement behavior of large droplets, a two-dimensional and compressible Navier-Stokes code was developed to determine the flow field around the test model. Also, the Eulerian-based droplet impingement model including a semi-empirical approach for the droplet-wall interaction process and droplet break-up was developed. In particular, the droplet-wall interactions were considered as numerical boundary conditions for the droplet impingement simulation in the supercooled large droplet conditions. Finally, the present results were compared with the experimental test data and the LEWICE results. The droplet impingement area and maximum collection efficiency values between present results and wind tunnel data were in good agreements. Otherwise, the inclination of collection efficiency of the present result is over-predicted than the wind tunnel data around a lower surface of the NACA 23012 airfoil.

Multi-Objective Optimization of Flexible Wing using Multidisciplinary Design Optimization System of Aero-Non Linear Structure Interaction based on Support Vector Regression

The static aeroelastic analysis and optimization of flexible wings are conducted for steady state conditions while both aerodynamic and structural parameters can be used as optimization variables. The system of multidisciplinary design optimization as a robust methodology to couple commercial codes for a static aeroelastic optimization purpose to yield a convenient adaptation to engineering applications is developed. Aspect ratio, taper ratio, sweepback angle are chosen as optimization variables and the skin thickness of the wing. The real-coded adaptive range multi-objective genetic algorithm code, which represents the global multi-objective optimization algorithm, was used to control the optimization process. The support vector regression(SVR) is applied for optimization, in order to reduce the time of computation. For this multi-objective design optimization problem, numerical results show that several useful Pareto optimal designs exist for the flexible wing.

Investigation of the Performance of Anti-Icing System of a Rotorcraft Engine Air Intake

Ice accretions on the surface around a rotorcraft air intake can deteriorate the safety of rotorcraft due to the engine performance degradation. The computational simulation based on modern CFD methods can be considered extremely valuable in analyzing icing effects before exact but very expensive icing wind tunnel or in-flight tests are conducted. In this study the range and amount of ice on the surface of anti-icing equipment are investigated for heat-on and heat-off modes. It is demonstrated through the computational prediction and the icing wind tunnel test that the maximum mass and height of ice of heat-on mode are reduced about 80% in comparison with those of heat-off mode.