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추력과 효율 향상을 위한 AUV Double Hydrofoil의 모션 최적설계
소현규(H.K. So),조태현(T.H. Jo),이용한(Y.H. Lee),김진산(J.S. Kim),한준희(J.H. Han),구본찬(B.C. Koo),이도형(D.H. Lee) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.1
While most AUV researches have concerned about single hydrofoil, practical AUV’s are generally operated with multiple hydrofoils. Double hydrofoil study attempts to evaluate thrust and efficiency with various flapping motions, and carries out design optimization using parametric analysis. Flow patterns such as vortex shedding and wake-body interaction are carefully investigated during design variable sensitivity analysis. The purpose of this design optimization is to find out the optimal motion that yields maximum thrust and efficiency. The design optimization employes several techniques such as table of orthogonal arrays, Kriging method, ANOVA analysis and MGA. Throughout this research, it is possible to find the optimal values of heaving ratio, heaving shift and pitch shift: Heaving ratio 0.950, heaving shift 23.120˚ and pitch shift 89.991˚ are found to be optimal values in double hydrofoil motions. Thrust and efficiency are 16.7% and 35.1% higher than existing AUV that did not consider nonlinear dependency of motion parameters. This results may offer an effective framework that is applicable to various AUV motion analyses and designs.
ENO interpolation 기반 분해과정을 활용한 다중해상도 유동해석 기법 연구
이용한(Y.H. Lee),조태현(T.H. Jo),구본찬(B.C. Koo),소현규(H.K. So),김도욱(D.W. Kim),이도형(D.H. Lee) 한국전산유체공학회 2018 한국전산유체공학회지 Vol.23 No.1
The improvement of decomposition process using Essentially Non-oscillation Decomposition (ENO) type subdivision scheme on multi-resolution analysis (MRA) based on wavelets basis is studied. The decomposition ability of conventional MRA has a numerical limitation in a flow that involves a shock. ENO interpolation is proposed to improve both decomposition ability and compression rate. The order of subdivision scheme in decomposition process is conserved by changing stencils in the same order. The proposed algorithm is applied to computational flow field around two-dimensional NACA0012 airfoil in subsonic, transonic and supersonic flow regime. Although all cases are improved in terms of compression rate, especially transonic and supersonic cases yield better result than subsonic case. Between transonic and supersonic cases, effects of ENO interpolation are appeared stronger in supersonic case due to the strength of shock. Therefore, it is confirmed that the MRA with ENO-based decomposition could improve the compression rate on flow which is involved a discontinuity.
구본찬(B. C. Koo),한준희(J. H. Han),조태현(T. H. Jo),박경현(K. H. Park),이도형(D. H. Lee) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.2
This paper attempts to evaluate the accuracy and efficiency of a design optimization procedure by combining wavelets-based multi resolution analysis method and proper orthogonal decomposition (POD) technique. Aerodynamic design procedure calls for high fidelity computational fluid dynamic (CFD) simulations and the consideration of large number of flow conditions and design constraints. Thus, even with significant computing power advancement, current level of integrated design process requires substantial computing time and resources. POD reduces the degree of freedom of full system by conducting singular value decomposition for various field simulations. In this research, POD combined Design Optimization model is proposed and its efficiency and accuracy are to be evaluated. For additional efficiency improvement of the procedure, multi resolution analysis method is also being employed during snapshot constructions (POD training period). The proposed design procedure was applied to the optimization of wing aerodynamic performance. Throughout the research, it was confirmed that the POD/MRA design procedure could significantly reduce the total design turnaround time and also capture all detailed complex flow features as in full order analysis.