Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μ the damping coefficient and V the local averaging flow velocity) are employed in this work to investigate the phenomenon...Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μ the damping coefficient and V the local averaging flow velocity) are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water waves.The numerical results are compared with experimental data available in the literature.The comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the resonant frequency reasonably well.However the conventional potential flow model(without artificial damping term) significantly over-predicts the wave height in narrow gaps around the resonant frequency.In order to calibrate the appropriate damping coefficient used for the potential model and make it work as well as the viscous fluid model in predicting the resonant wave height in narrow gaps but with little computational efforts,the dependence of damping coefficient μ on the body geometric dimensions is examined considering the parameters of gap width Bg,body draft D,body breadth ratio Br and body number n(n = 2,3),where Br = BB/BA for the case of two bodies(Body A and Body B) with different breadths of BA and BB,respectively.It was confirmed that the damping coefficient used for the potential flow model is not sensitive to the geometric dimensions and spatial arrangement.It was found that μ∈ [0.4,0.5] may guarantee the variation of Hg/H0 with kh to be generally in good agreement with the experimental data and the results of viscous fluid model,where Hg is the excited wave height in narrow gaps under various dimensionless incident wave frequencies kh,H0 is the incident wave height,k = 2π/L is the wave number and h is the water depth.展开更多
通过变分方法在光滑有界域Ω上研究由常数a,b>0,参数λ>0及连续函数f(x,u)共同决定的非局部问题:{-(a-b integral from Ω|▽u|~2dx)Δu+bλu^3=f(x,u)x∈Ω u=0 x∈Ω利用Ekeland变分原理和山路引理得到该问题近共振情形多重...通过变分方法在光滑有界域Ω上研究由常数a,b>0,参数λ>0及连续函数f(x,u)共同决定的非局部问题:{-(a-b integral from Ω|▽u|~2dx)Δu+bλu^3=f(x,u)x∈Ω u=0 x∈Ω利用Ekeland变分原理和山路引理得到该问题近共振情形多重解的存在性.展开更多
A novel single-ended online fault location algorithm is investigated for DC distribution networks. The proposed algorithm calculates the fault distance based on the characteristics of the voltage resonance. The Prony&...A novel single-ended online fault location algorithm is investigated for DC distribution networks. The proposed algorithm calculates the fault distance based on the characteristics of the voltage resonance. The Prony's method is introduced to extract the characteristics. A novel method is proposed to solve the pseudo dual-root problem in the calculation process. The multiple data windows are adopted to enhance the robustness of the proposed algorithm. An index is proposed to evaluate the accuracy and validity of the results derived from the various data windows. The performances of the proposed algorithm in different fault scenarios were evaluated using the PSCAD/EMTDC simulations. The results show that the algorithm can locate the faults with transient resistance using the 1.6 ms data of the DC-side voltage after a fault inception and offers a good precision.展开更多
基金supports from the Natural National Science Foundation of China (Grant Nos.50909016,50921001 and 10802014)support of ARC Discovery Project Program (Grant No. DP0557060)supported by the Open Fund from the State Key Laboratory of Structural Analysis for Industrial Equipment (Grant No. GZ0909)
文摘Viscous fluid model and potential flow model with and without artificial damping force(f=-μV,μ the damping coefficient and V the local averaging flow velocity) are employed in this work to investigate the phenomenon of fluid resonance in narrow gaps between multi-bodies in close proximity under water waves.The numerical results are compared with experimental data available in the literature.The comparison demonstrates that both the viscous fluid model and the potential flow model are able to predict the resonant frequency reasonably well.However the conventional potential flow model(without artificial damping term) significantly over-predicts the wave height in narrow gaps around the resonant frequency.In order to calibrate the appropriate damping coefficient used for the potential model and make it work as well as the viscous fluid model in predicting the resonant wave height in narrow gaps but with little computational efforts,the dependence of damping coefficient μ on the body geometric dimensions is examined considering the parameters of gap width Bg,body draft D,body breadth ratio Br and body number n(n = 2,3),where Br = BB/BA for the case of two bodies(Body A and Body B) with different breadths of BA and BB,respectively.It was confirmed that the damping coefficient used for the potential flow model is not sensitive to the geometric dimensions and spatial arrangement.It was found that μ∈ [0.4,0.5] may guarantee the variation of Hg/H0 with kh to be generally in good agreement with the experimental data and the results of viscous fluid model,where Hg is the excited wave height in narrow gaps under various dimensionless incident wave frequencies kh,H0 is the incident wave height,k = 2π/L is the wave number and h is the water depth.
基金supported by the National Basic Research Program of China("973" Project)(Grant No.2012CB215206)the National Natural Science Foundation of China(Grant Nos.51407067&51222703)the "111" Project of China(Grant No.B08013)
文摘A novel single-ended online fault location algorithm is investigated for DC distribution networks. The proposed algorithm calculates the fault distance based on the characteristics of the voltage resonance. The Prony's method is introduced to extract the characteristics. A novel method is proposed to solve the pseudo dual-root problem in the calculation process. The multiple data windows are adopted to enhance the robustness of the proposed algorithm. An index is proposed to evaluate the accuracy and validity of the results derived from the various data windows. The performances of the proposed algorithm in different fault scenarios were evaluated using the PSCAD/EMTDC simulations. The results show that the algorithm can locate the faults with transient resistance using the 1.6 ms data of the DC-side voltage after a fault inception and offers a good precision.
