The wind power potential in Interior Alaska is evaluated from a micrometeorological perspective. Based on the local balance equation of momentum and the equation of continuity we derive the local balance equation of k...The wind power potential in Interior Alaska is evaluated from a micrometeorological perspective. Based on the local balance equation of momentum and the equation of continuity we derive the local balance equation of kinetic energy for macroscopic and turbulent systems, and in a further step, Bernoulli’s equation and integral equations that customarily serve as the key equations in momentum theory and blade-element analysis, where the Lanchester-Betz-Joukowsky limit, Glauert’s optimum actuator disk, and the results of the blade-element analysis by Okulov and Sorensen are exemplarily illustrated. The wind power potential at three different sites in Interior Alaska (Delta Junction, Eva Creek, and Poker Flat) is assessed by considering the results of wind field predictions for the winter period from October 1, 2008, to April 1, 2009 provided by the Weather Research and Forecasting (WRF) model to avoid time-consuming and expensive tall-tower observations in Interior Alaska which is characterized by a relatively low degree of infrastructure outside of the city of Fairbanks. To predict the average power output we use the Weibull distributions derived from the predicted wind fields for these three different sites and the power curves of five different propeller-type wind turbines with rated powers ranging from 2 MW to 2.5 MW. These power curves are represented by general logistic functions. The predicted power capacity for the Eva Creek site is compared with that of the Eva Creek wind farm established in 2012. The results of our predictions for the winter period 2008/2009 are nearly 20 percent lower than those of the Eva Creek wind farm for the period from January to September 2013.展开更多
The unified solutions are presented for stresses and displacements around a circular tunnel subjected to a hydrostatic stress field.The rock mass is assumed to be elastic-brittle-plastic and governed by the Unified St...The unified solutions are presented for stresses and displacements around a circular tunnel subjected to a hydrostatic stress field.The rock mass is assumed to be elastic-brittle-plastic and governed by the Unified Strength Theory.The displacements are obtained accounting for three different definitions for elastic strains and different Young's modulus in the plastic zone.The unified solutions obtained in this paper are especially versatile in reflecting the intermediate principal stress effect to different extents for different materials.The conventional solutions,based on the Mohr-Coulomb failure criterion and the Generalized Twin Shear Stress yield criterion,are special cases of the present unified solutions.The new unified solutions can compare with those computed by the latest generalized Hoek-Brown failure criterion.The results obtained demonstrate the importance of the intermediate principal stress influence for the stresses and displacements analysis.The effects of different definitions for elastic strains and different Young's modulus in the plastic zone on the displacements are significant.展开更多
基金the National Science Foundation for funding the project work of Megan Hinzman and Samuel Smock in summer 2011Hannah K.Ross and John Cooney in summer 2012 through the Research Experience for Undergraduates(REU)Program,grant number AGS1005265the Alaska Department of Labor for funding Dr.Gary Sellhorst’s project work
文摘The wind power potential in Interior Alaska is evaluated from a micrometeorological perspective. Based on the local balance equation of momentum and the equation of continuity we derive the local balance equation of kinetic energy for macroscopic and turbulent systems, and in a further step, Bernoulli’s equation and integral equations that customarily serve as the key equations in momentum theory and blade-element analysis, where the Lanchester-Betz-Joukowsky limit, Glauert’s optimum actuator disk, and the results of the blade-element analysis by Okulov and Sorensen are exemplarily illustrated. The wind power potential at three different sites in Interior Alaska (Delta Junction, Eva Creek, and Poker Flat) is assessed by considering the results of wind field predictions for the winter period from October 1, 2008, to April 1, 2009 provided by the Weather Research and Forecasting (WRF) model to avoid time-consuming and expensive tall-tower observations in Interior Alaska which is characterized by a relatively low degree of infrastructure outside of the city of Fairbanks. To predict the average power output we use the Weibull distributions derived from the predicted wind fields for these three different sites and the power curves of five different propeller-type wind turbines with rated powers ranging from 2 MW to 2.5 MW. These power curves are represented by general logistic functions. The predicted power capacity for the Eva Creek site is compared with that of the Eva Creek wind farm established in 2012. The results of our predictions for the winter period 2008/2009 are nearly 20 percent lower than those of the Eva Creek wind farm for the period from January to September 2013.
文摘The unified solutions are presented for stresses and displacements around a circular tunnel subjected to a hydrostatic stress field.The rock mass is assumed to be elastic-brittle-plastic and governed by the Unified Strength Theory.The displacements are obtained accounting for three different definitions for elastic strains and different Young's modulus in the plastic zone.The unified solutions obtained in this paper are especially versatile in reflecting the intermediate principal stress effect to different extents for different materials.The conventional solutions,based on the Mohr-Coulomb failure criterion and the Generalized Twin Shear Stress yield criterion,are special cases of the present unified solutions.The new unified solutions can compare with those computed by the latest generalized Hoek-Brown failure criterion.The results obtained demonstrate the importance of the intermediate principal stress influence for the stresses and displacements analysis.The effects of different definitions for elastic strains and different Young's modulus in the plastic zone on the displacements are significant.
