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| 1 | Numerical analysis and optimization of boundary layer suction on airfoils显示文摘Numerical approach of hybrid laminar flow control(HLFC) is investigated for the suction hole with a width between 0.5 mm and 7 mm. The accuracy of Menter and Langtry's transition model applied for simulating the flow with boundary layer suction is validated. The experiment data are compared with the computational results. The solutions show that this transition model can predict the transition position with suction control accurately. A well designed laminar airfoil is selected in the present research. For suction control with a single hole, the physical mechanism of suction control, including the impact of suction coefficient and the width and position of the suction hole on control results, is analyzed. The single hole simulation results indicate that it is favorable for transition delay and drag reduction to increase the suction coefficient and set the hole position closer to the trailing edge properly. The modified radial basis function(RBF) neural network and the modified differential evolution algorithm are used to optimize the design for suction control with three holes. The design variables are suction coefficient, hole width, hole position and hole spacing. The optimization target is to obtain the minimum drag coefficient. After optimization,the transition delay can be up to 17% and the aerodynamic drag coefficient can decrease by 12.1%. | Shi Yayun Bai Junqiang Hua Jun Yang Tihao | 2015 | Chinese Journal of Aeronautics2015，28，2： | 12 |
| 2 | Transition prediction and sensitivity analysis for a natural laminar flow wing glove flight experiment显示文摘Natural laminar flow technology can significantly reduce aircraft aerodynamic drag and has excellent technical appeal for transport aircraft development with high aerodynamic efficiency.Accurately and efficiently predicting the laminar-to-turbulent transition and revealing the maintenance mechanism of laminar flow in a transport aircraft’s flight environment are significant for developing natural laminar flow wings.In this research,we carry out natural laminar flow flight experiments with different Reynolds numbers and angles of attack.The critical N-factor is calibrated as 9.0 using flight experimental data and linear stability theory from a statistical perspective,which makes sure that the relative error of transition location is within 5%.We then implement a simplified e^(N) transition prediction method with a similar accuracy compared with linear stability theory.We compute the sensitivity information for the simplified eN method with an adjointbased method,using the automatic differentiation technique(ADjoint).The impact of Reynolds numbers and pressure distributions on TS waves is analyzed using the sensitivity information.Through the sensitivity analysis,we find that:favorable pressure gradients not only suppress the development of TS waves but also decrease their sensitivity to Reynolds numbers;there exist three special regions which are very sensitive to the pressure distribution,and the sensitivity decreases as the local favorable pressure gradient increases.The proposed sensitivity analysis method enables robust natural laminar flow wings design. | Tihao YANG Hai ZHONG Yifu CHEN Yayun SHI Junqiang BAI Feifei QIN | 2021 | Chinese Journal of Aeronautics2021，34，8： | 5 |
| 3 | Scalable rate control for MPEG-4 video显示文摘 | Lee HungJun Chiang Tihao Zhang Yaqi | 2000 | IEEE Trans on Circuit Syst for Video Technol2000，10，6： | 1 |
| 4 | Content-Aware Adaptive Media Playout Controls for Wireless Video Streaming显示文摘 | Hsiao-Chiang Chuang ChingYao Huang Tihao Chiang | | 0，，06： | 1 |
| 5 | Scalable rate control for MPEG-4 video显示文摘 | Hung-Ju Lee Tihao Chiang Zhang Ya-Qin | 2000 | IEEE2000，10，6： | 1 |
| 6 | New fast binary pyramid motion estimation for MPEG2 and HDTV encoding 显示文摘 | SONG Xudong CHIANG Tihao LEE Xiaobing | 2000 | IEEE Trans on Circuits Syst Video Technol2000，10，7： | 1 |
| 7 | A Zerotree Wavelet Video Coder 显示文摘 | Stephen A Martucci Iraj Sodagar Tihao Chiang | 1997 | 1EEE Trans on Circuits and Systems for Video Technology1997，7，1： | 1 |
| 8 | Scalable Rate Control for MPEG-4 Video显示文摘 | Lee Hung-ju Chiang Tihao Zhang Ya-qin | 2000 | IEEE Transactions on Circuits and Systems forVideoTeehnology2000，10，6： | 1 |
| 9 | A new rate control scheme using quadratic rate distortion model显示文摘 | Chiang Tihao and Zhang Ya-Qin | 1997 | Circuits and Systems for Video Technology IEEE Transactions on1997，7，1： | 1 |
| 10 | Scalable rate control for MPEG-4 video 显示文摘 | Chiang Tihao Zhang Yaqin | 2000 | IEEE Transactions on Circuits and Systems for Video Technology2000，10，6： | 1 |
| 11 | An overview of the encoding tools in the MPEG-4 reference software显示文摘 | Tihao Chiang Hung_Ju Lee Huifang Sun | 2000 | Intemational Symposium on Circuits and Systems2000，2831，： | 1 |
| 12 | Scalable Rate Control for MPEG-4 Video显示文摘 | Hung-Ju Lee Tihao Chiang Ya-Qin Zhang | 2000 | IEEE Transactions on Circuits AND Systems for Video Technology2000，10，6： | 1 |
| 13 | Hierarchical HDTV/SDTV compatible coding using Kalman statistical filtering 显示文摘 | Chiang Tihao Anastassiou D | 1999 | IEEE Transactions on Circuits and Systems for Video Technology1999，4，9： | 1 |
| 14 | A new rate control scheme using quadratic rate distortion model 显示文摘 | Chiang Tihao Zhang Ya-qin | 1997 | IEEE Transactions on Circuits and Systems for Video Technology1997，7，1： | 1 |
| 15 | Scalable rate control for MPEG-4 video显示文摘 | Lee Hung-ju Chiang Tihao Zhang Ya-qin | 2000 | IEEE Transactions on Circuits and Systems for Video Technology2000，10，6： | 1 |
| 16 | A new rate control scheme using quadratic rate distortion model显示文摘 | Chiang Tihao Zhang Yaqin | 1997 | IEEE Trans on Circuits Syst for Video Teehnol1997，7，1： | 1 |
| 17 | Scalable Rate Control for MPEG-4 Video显示文摘 | Lee Hungju Chiang Tihao Zhang Yaqin | 2000 | IEEE Transactions on Circuits and Systems for Video Technology2000，10，6： | 1 |
| 18 | Adjoint-based robust optimization design of laminar flow wing under flight condition uncertainties显示文摘It is an inherent uncertainty problem that the application of laminar flow technology to the wing of large passenger aircraft is affected by flight conditions.In order to seek a more robust natural laminar flow control effect,it is necessary to develop an effective optimization design method.Meanwhile,attention must be given to the impact of crossflow(CF)instability brought on by the sweep angle.This paper constructs a robust optimization design framework based on discrete adjoint methods and non-intrusive polynomial chaos.Transition prediction is implemented by coupled Reynolds-Averaged Navier-Stokes(RANS)and simplified e^(N)method,which can consider both Tollmien-Schlichting(TS)wave and crossflow vortex instability.We have performed gradient enhancement processing on the general Polynomial Chaos Expansion(PCE),which is advantageous to reduce the computational cost of single uncertainty propagation.This processing takes advantage of the gradient information obtained by solving the coupled adjoint equations considering transition.The statistical moment gradient solution used for the robust optimization design also uses the derivatives of coupled adjoint equations.The framework is applied to the robust design of a 25°swept wing with infinite span in transonic flow.The uncertainty quantification and sensitivity analysis on the baseline wing shows that the uncertainty quantification method in this paper has high accuracy,and qualitatively reveals the factors that dominate in different flow field regions.By the robust optimization design,the mean and standard deviation of the drag coefficient can be reduced by 29%and 45%,respectively,and compared with the deterministic optimization design results,there is less possibility of forming shock waves under flight condition uncertainties.Robust optimization results illustrate the trade-off between the transition delay and the wave drag reduction. | Yifu CHEN Hanyue RAO Yiju DENG Tihao YANG Yayun SHI Junqiang BAI | 2023 | Chinese Journal of Aeronautics2023，36，6： | 0 |
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