scholarly journals Zombie Vortex Instability. III. Persistence with Nonuniform Stratification and Radiative Damping

2018 ◽  
Vol 869 (2) ◽  
pp. 127 ◽  
Author(s):  
Joseph A. Barranco ◽  
Suyang Pei ◽  
Philip S. Marcus
1976 ◽  
Vol 75 (1) ◽  
pp. 1-15 ◽  
Author(s):  
J. A. Cole

Critical speeds for the onset of Taylor vortices and for the later development of wavy vortices have been determined from torque measurements and visual observations on concentric cylinders of radius ratios R1/R2 = 0·894–0·954 for a range of values of the clearance c and length L: c/R1 = 0·0478–0·119 and L/c = 1–107. Effectively zero variation of the Taylor critical speed with annulus length was observed. The speed at the onset of wavy vortices was found to increase considerably as the annulus length was reduced and theoretical predictions are realistic only for L/c values exceeding say 40. The results were similar for all four clearance ratios examined. Preliminary measurements on eccentrically positioned cylinders with c/R1 = 0·119 showed corresponding effects.


2014 ◽  
Vol 497 ◽  
pp. 62-66 ◽  
Author(s):  
Xingyi Zhang ◽  
Jun Zhou ◽  
Donghua Yue ◽  
Wei Liu ◽  
Youhe Zhou

2017 ◽  
Vol 24 (10) ◽  
pp. 103302 ◽  
Author(s):  
Rishi R. Pandit ◽  
Edward Ackad ◽  
Emmanuel d'Humieres ◽  
Yasuhiko Sentoku
Keyword(s):  

Author(s):  
Albert Ruprecht ◽  
Ralf Neubauer ◽  
Thomas Helmrich

The vortex instability in a spherical pipe trifurcation is investigated by applying a Very Large Eddy Simulation (VLES). For this approach an new adaptive turbulence model based on an extended version of the k-ε model is used. Applying a classical Reynolds-averaged Navier-Stokes-Simulation with the standard k-ε model is not able to forecast the vortex instability. However the prescribed VLES method is capable to predict this flow phenomenon. The obtained results show a reasonable agreement with measurements in a model test.


Author(s):  
I. Yu. Kostyukov ◽  
E. N. Nerush ◽  
A. G. Litvak
Keyword(s):  

Author(s):  
R. Döttling ◽  
J. Eßlinger ◽  
W. Lay ◽  
A. Seeger
Keyword(s):  

2015 ◽  
pp. 325-359
Author(s):  
Jie-Zhi Wu ◽  
Hui-Yang Ma ◽  
Ming-De Zhou

Author(s):  
G. F. Efremov ◽  
M. A. Novikov ◽  
V. V. Ivanov ◽  
A. G. Efremov
Keyword(s):  

2019 ◽  
Vol 7 (5) ◽  
pp. 134 ◽  
Author(s):  
Rui He ◽  
Ji Ji ◽  
Jisheng Zhang ◽  
Wei Peng ◽  
Zufeng Sun ◽  
...  

With the development of offshore wind energy in China, more and more offshore wind turbines are being constructed in rock-based sea areas. However, the large diameter and thin-walled steel rock-socketed monopiles are very scarce at present, and both the construction and design are very difficult. For the design, the dynamic safety during the whole lifetime of the wind turbine is difficult to guarantee. Dynamic safety of a turbine is mostly controlled by the dynamic impedances of the rock-socketed monopile, which are still not well understood. How to choose the appropriate impedances of the socketed monopiles so that the wind turbines will neither resonant nor be too conservative is the main problem. Based on a numerical model in this study, the accurate impedances are obtained for different frequencies of excitation, different soil and rock parameters, and different rock-socketed lengths. The dynamic stiffness of monopile increases, while the radiative damping decreases as rock-socketed depth increases. When the weathering degree of rock increases, the dynamic stiffness of the monopile decreases, while the radiative damping increases.


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