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8.4.14 Choi

50th NIA CFD Seminar:

Dr. Seongim Choi, Assistant Professor, Virginia Tech
August 4, 2014, 2:00 pm, NIA, Rm 137
Hosts: Boris Diskin and Hiro Nishikawa (NIA)

Simulation-based design optimization method depends heavily on the specifics of aerospace vehicle system and flow characteristics at design points. This talk focuses on how different design optimization methods with aerodynamic analysis of various fidelities and sensitivity analysis are utilized for rotary and fixed wing vehicles: a helicopter rotor in forward flight and a low-boom supersonic jet. If time permits, a design application of low-noise co-axial contra-rotating rotor, i.e., open rotor, in consideration of aleatory uncertainties will be introduced as a design extension for rotor flows. First, an efficient CFD method to optimize helicopter rotor at unsteady forward flight, a time-spectral and adjoint-based optimization method, is developed. A direct application of the optimization techniques common to the steady flow problems to the unsteady flows is difficult, as the flows are complicated and design cost is very high in resolving transient, time-varying aerodynamic performances. The time-spectral method is based on the frequency-domain analysis and reduces the unsteady form of the Navier-Stokes governing equations into a periodic steady state. A powerful adjoint solution method can be effectively integrated into the unsteady design framework for helicopter rotors through the time-spectral formulation of the equations. The design framework of time-spectral and adjoint-based method can be applied to many areas of the engineering design problems including co-axial contra-rotating open rotor, wind-turbine blade and flapping wing. Next, a multi-fidelity and multidisciplinary design optimization method for supersonic business jets (SBJ) is introduced. Optimal shape and mission profile of SBJ are sought to reduce sonic boom on the ground during the cruise condition. Inviscid Euler computation with solution-adaptive mesh refinement is utilized, and gradient-free optimization is used in combination with multi-fidelity response surface model.

Dr. Seongim Choi is currently an Assistant Professor in the dept. of Aerospace and Ocean Engineering, Virigina Tech. Prior to working in Virginia Tech, she worked as an Assistant Professor in Korea Advanced Institute of Science and Technology (KAIST) from 2010~2013. She received her Ph.D from Stanford in 2006, and B.S. and M.S. from Seoul National University. She received an AIAA MDO best paper award for her Ph.D work on the MDO of low-boom supersonic jets. She worked as a post doctorate fellow in the U.S. Aeroflightdynamics Directorate (AFDD) working on helicopter rotor flow analysis and design. She received a young investigated award from the 1st Asian Rotorcraft Forum in 2012 for her work on the time-spectral and adjoint-based design method for helicopter rotor flows.



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