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이진익(J.I. Lee),이은석(E.S. Lee),전병을(B.E. Jun),이광섭(K.S. Lee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
This paper shows the optimization techniques for the determination of the number of sensors to estimate the flow states on the flow field. The flow states by a state estimator is fed back to input in the flow controller. Usually a series of pressure sensors mounted on the surface is used as a flow measurement device. To minimize the number of sensors, it is necessary to maximize the sensing effect by optimization of their placement with the state estimator point of view. The performance index for optimizing is thus constructed with the estimation errors. The results provide the optimal sensor positions as well as the optimal number sensors.
이진익(J.I. Lee),이은석(E.S. Lee),전병을(B.E. Jun),이광섭(K.S. Lee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
A series of the frequency response analysis of the BFS(Backward Facing Step) flow field, is peformed from the control point of view. We have made a close investigation of the flow field model step by step in constructing a flow control loop. First the vortex flow at the natural free stream state is characterized. The changes by reduced order modeling using the POD method are analyzed. Consecutively it is compared the frequency responses of the vortices before and after the forcing inputs. Finally the frequency characteristics of the flow field model with an ANN-ARX(Artificial Neural Network-Autoregressive Exogenous) structure for the low order modeling are analyzed in detail.
다변수 재귀형 최소자승 알고리즘을 이용한 유동 상태 추정기 설계
이진익(J.I. Lee),이은석(E.S. Lee),전병을(B.E. Jun),이광섭(K.S. Lee) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.11
This paper presents design technique for a flow field estimator in the sense of LSE(least square estimation). In order for taking into account the strongly nonlinearity of the flow field model, the dimension of the estimator is increased by introducing the recursive form of the estimated states. Database normalization by standard deviation is also used to enhance the condition number of the covariance matrix. The proposed multi-variable recursive estimator for flow state estimation is promising for the real time implementation compared to the neural network based one. Moreover simulation results show the performance improvements are remarkable than the least square estimation.
이진익(J.I. Lee),이은석(E.S. Lee),이광섭(K.S. Lee),전병을(B.E. Jun) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.11
Error analysis in the reduction of BFS(Backward Facing Phase) flow field is dealt with in this paper. The POD(Proper Orthogonal Decomposition) technique is adopted in reduced order modeling of flow field from a bunch of flow snapshots. It is well-known for capturing the global flow states rather than local optimum ones. In order for the modeling of the flow field on BFS, the open loop forcing data set are used in the modeling study. The reduced global states from all test snapshots are compared with the local optimal states from individual one for each test case. By analyzing not only the reconstruction errors but also the POD modes, we analyze the reduced order modeling of flow field in detail.
유동 상태추정을 위한 센서위치 최적화 기법에 관한 연구
이진익(J.I. Lee),이은석(E.S. Lee),전병을(B.E. Jun),이광섭(K.S. Lee) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.11
An optimization technique for the placement of a series of pressure sensors to be installed on the surface of the BFS structure is proposed. A state estimator based on LSE(least square estimation) using the surface pressure measured by the sensors is designed for the estimation of the eigen-modes of the density in the flow field. Numerical optimization minimizing the weighted mean-square-error of the states is formulated for the optimal sensor position. By comparing the optimum solution with the considerable positions by intuition at which the power strength of POD modes are maximum, we summarized the policy for the sensor placement from the flow control point of view.
이충연(C.Y. Lee),사정환(J.H. Sa),박수형(S.H. Park),이은석(E.S. Lee),이진익(J.I. Lee),이광섭(K.S. Lee) 한국전산유체공학회 2012 한국전산유체공학회지 Vol.17 No.4
Effects of the subgrid length-scale in the Delayed-Detached Eddy Simulation(DDES) are investigated based on the Spalart-Allmaras(S-A) and the k-ω Shear Stress Transport(SST) turbulence models. Driver & Seegmillers experimental results are used to validate numerical results. Grid convergence with grid resolution and subgrid length-scale is investigated. The simulation results show that the volume method for the subgrid length-scale is more resistant to unfavorable effects of the grid size in the periodic direction than the maximum method. Using a sufficient grid resolution and an appropriate subgrid length-scale, both S-A based DDES and SST based DDES methods can provide a good correlation with the experimental data.
비대칭와류 제어기의 Open-Loop 거동 전산해석 및 풍동시험과의 비교
이은석(E. Lee),이광섭(K.S Lee),이진익(J.I. Lee) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
The open-loop behavior of the flow actuator for the control of the asymmetric vortex at high angle of attack are simulated using the Cobalt code. Response of the side force to various levels of step inputs and various durations of duty cycle inputs are simulated and compared with wind tunnel measurements, which showed that the simulation well reproduced the measured open-loop dynamic behavior.
전산해석을 통한 비대칭 와류 제어용 구동기의 작용 기전 분석
이은석(E.S. Lee),이진익(J.I. Lee),이광섭(K.S. Lee) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.11
The behavior of the blowing actuator used for the body vortex control is investigated through unsteady and laminar Navier-Stokes computation at the base-diameter referenced Reynolds number (ReD) of 220,000 and the angle if attack of 50 deg. It is observed that the blowing actuator promotes the flow separation on its actuation and thereafter produces the side force.