Kyunghyun Park

Multidisciplinary Design Optimization(MDO) of a Medium-Sized Solar Powered HALE UAV Considering Energy Balancing

A MDO study of a midium-sized solar powered High Altitude Long Endurance (HALE) UAV has been performed, focused on energy balance. In the MDO process, Vortex Lattice Method(VLM) is employed for the aerodynamic modeling of the vehicle, of which structural weight is estimated with the modeling proposed by Cruz. Tail volume ratios have been set as constants, while the location of tail surfaces is determined from longitudinal static stability criterion. By balancing the available energy from solar cells, battery, and altitude, with the energy-requirement of the vehicle, the possibility of continuous flight over 24-hours has been investigated. The solar radiation level is set as that of summer at the latitude of north. During the daytime, the aircraft climbs using solar energy, accumulating potential energy, which supplements energy balance during the night. Optimizations have been sought in size of the vehicle, its weight distribution, and flight strategy.

Fluid-Structure Interaction and Design Optimization of HAR wing for Endurance efficiency of S-HALE aircraft

In this paper, S-HALE aircraft wing sizing optimization is conducted at 20km altitude by modifying 3 variables including span length, aspect ratio and weight distribution along the spanwise direction of the wing for 24-hour continuous flight. Fluid-Structural Interaction is conducted for static stability of wing and high estimation of aerodynamic performance. 3dimensional Euler equation and MSC.Nastran are used for aerodynamic and structural analysis. Finally we check the energy flow of S-HALE during a day and confirme that the SHALE can fly 24-hour continuously.

Aeroelastic Characteristics of High-Aspect-Ratio Wing According to Wing Shape

Strong interactions occur between aerodynamic characteristics and structural deformation for High-Aspect-Ratio Wing. On this account, a parametric study on aeroelastic characteristics of High-Aspect-Ratio wing is performed for various wing shapes. Wing models with different taper ratio and sweepback angle are selected as subjects and their performances were compared with baseline model. To perform Fluid/Structure Interaction analysis, CFD analysis based on the three-dimensional Euler equations and FEM analysis using MSC Nastran are used. As a result, wing models which have constant chord with tapered outer section had the highest lift coefficient among wing models. And they experienced less wing tip deflection than baseline shape. Therefore, they have superior aeroelastic characteristics and are the most suitable shape for optimization. Nomenclature xi = chordwise coordinate of a structural nodal point yi = spanwise coordinate of a structural nodal point fi = nodal force acting on the i th nodal point wi = weighting factor N = the number of structural nodes C = chord length L = span length Cp = pressure coefficient

Research on the Adaptive Wavelet Method for the Enhancement of Computational Efficiency of Three Dimensional Flows

The adaptive wavelet method is studied for the enhancement of computational efficiency of three-dimensional flows. Three-dimensional wavelet decomposition process is introduced based on the previous two-dimensional method. The order of numerical accuracy of an original solver is preserved by applying a proper thresholding technique. The proposed algorithm is applied to the computation of flow field around ONERA-M6 wing in transonic regime. Through the application, it is confirmed that the three-dimensional adaptive wavelet method can reduce the computational time with conserving the numerical accuracy of an original solver.

The Application of Adaptive Wavelet Method to Multi-Dimensional Limiting Process for Enhancement of Computational Efficiency

An adaptive wavelet method is applied in order to enhance the computational efficiency of enhanced Multi-dimensional Limiting Process (e-MLP) without deterioration of the numerical accuracy of original Computational Fluid Dynamics (CFD) scheme. For this purpose, higher order of adaptive wavelet method is constructed including higher order of wavelet decomposition and modified thresholding. Besides, the locations of crucial features such as shock, vortex core, etc. are automatically and accurately searched in the CFD dataset through wavelet transformation. Only on these locations, high order spatial interpolation scheme with e-MLP are performed; in the other locations, interpolation method is utilized to compute residual values, which reduces the computational time of flux evaluation. This high order adaptive wavelet method was applied to unsteady Euler flow computations such as shock-vortex interaction problem. Throughout these processes, it was verified that computational efficiency was enhanced with preservation of numerical accuracy of CFD solver.Copyright

Design Optimization of Transonic Wing/Fuselage System Using Proper Orthogona1 Decomposition

This paper presents a validation of the accuracy of a reduced order model(ROM) and the efficiency of the design optimization using a Proper Orthogonal Decomposition(POD) to transonic wing/fuselage system. Three dimensional Euler equations are solved to extrude snapshot data of the full order aerodynamic analysis, and then a set of POD basis vectors reproducing the behavior of flow around the wing/fuselage system is calculated from these snapshots. In this study, reduced order model constructed through this procedure is applied to several validation cases, and then it is confirmed that the ROM has the capability of the prediction of flow field in the space of interest. Additionally, after the design optimization of the wing/fuselage system with the ROM is performed, results of the ROM are compared with results of the design optimization using response surface model(RSM). From these, it can be confirmed that the design optimization with the ROM is more efficient than RSM.