This paper numerically and experimentally investigates the hydrodynamic interaction between two semi-submersible type VLFS modules in the frequency domain. Model tests were conducted to investigate the relationship be...This paper numerically and experimentally investigates the hydrodynamic interaction between two semi-submersible type VLFS modules in the frequency domain. Model tests were conducted to investigate the relationship between interactions and wave headings. Numerical studies were performed by solving the radiation-diffraction problem and were validated against the experimental results. Motion Response Amplitude Operators (RAOs) were obtained from numerical and experimental studies. The dependency of the hydrodynamic interaction effect on wave headings is clarified. The influence of different wave periods on the motion responses of two-module VLFS and wave elevations in the gap is studied. The results indicate that the hydrodynamic interactions of the two modules are directly related to the wave headings and the periods of the incident wave. The shielding effect plays an important role in short wave, and the influence decreases with the increase of the incident wavelength. The numerical results based on the diffraction-radiation code can give a relatively good estimation to the responses in short wave while for long wave, it would over-predict the response.展开更多
The main purpose of the work presented here is to evaluate different methods for quality control of polymeric insulated HVDC cables.The insight gained can be used to evaluate proposed test methods for quality assuranc...The main purpose of the work presented here is to evaluate different methods for quality control of polymeric insulated HVDC cables.The insight gained can be used to evaluate proposed test methods for quality assurance of long lengths of polymer insulated power cables.Laboratory experiments were performed using both Rogowski shaped test objects and model cables,insulated with XLPE containing imbedded spherically shaped particles.Tests were performed by stressing the test object with AC(50 Hz),VLF(0.1 Hz) and DC voltages and measuring time to breakdown at the different voltages.The slope of the voltage-time curve for 0.1 and 50 Hz were found to be parallel showing higher breakdown strength for 0.1 Hz than 50 Hz.The number of periods to breakdown is somewhat higher for 0.1 Hz than for 50 Hz.The breakdown strength for DC was much higher than for both AC 50 Hz and 0.1 Hz.The results indicate that the VLF test voltage needs to be 2 to 3 times higher than at 50 Hz power frequency in order to eliminate the same defects within a comparable time.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51709170 and 51979167)the Ministry of Industry and Information Technology of China(Mooring position technology:floating support platform engineering(Ⅱ))+1 种基金the Shanghai Sailing Program(Grant No.17YF1409700)the China Scholarship Council(Grant No.201806230206)
文摘This paper numerically and experimentally investigates the hydrodynamic interaction between two semi-submersible type VLFS modules in the frequency domain. Model tests were conducted to investigate the relationship between interactions and wave headings. Numerical studies were performed by solving the radiation-diffraction problem and were validated against the experimental results. Motion Response Amplitude Operators (RAOs) were obtained from numerical and experimental studies. The dependency of the hydrodynamic interaction effect on wave headings is clarified. The influence of different wave periods on the motion responses of two-module VLFS and wave elevations in the gap is studied. The results indicate that the hydrodynamic interactions of the two modules are directly related to the wave headings and the periods of the incident wave. The shielding effect plays an important role in short wave, and the influence decreases with the increase of the incident wavelength. The numerical results based on the diffraction-radiation code can give a relatively good estimation to the responses in short wave while for long wave, it would over-predict the response.
文摘The main purpose of the work presented here is to evaluate different methods for quality control of polymeric insulated HVDC cables.The insight gained can be used to evaluate proposed test methods for quality assurance of long lengths of polymer insulated power cables.Laboratory experiments were performed using both Rogowski shaped test objects and model cables,insulated with XLPE containing imbedded spherically shaped particles.Tests were performed by stressing the test object with AC(50 Hz),VLF(0.1 Hz) and DC voltages and measuring time to breakdown at the different voltages.The slope of the voltage-time curve for 0.1 and 50 Hz were found to be parallel showing higher breakdown strength for 0.1 Hz than 50 Hz.The number of periods to breakdown is somewhat higher for 0.1 Hz than for 50 Hz.The breakdown strength for DC was much higher than for both AC 50 Hz and 0.1 Hz.The results indicate that the VLF test voltage needs to be 2 to 3 times higher than at 50 Hz power frequency in order to eliminate the same defects within a comparable time.
