Turbulent flow in a 3-D blade passage of a Francis hydro turbine was simulated with the Large Eddy Simulation （LES） to investigate the spatial and temporal distributions of the turbulence when strongly distorted wak...Turbulent flow in a 3-D blade passage of a Francis hydro turbine was simulated with the Large Eddy Simulation （LES） to investigate the spatial and temporal distributions of the turbulence when strongly distorted wakes in the inflow sweep over the passage, In a suitable consideration of the energy exchanging mechanism between the large and small scales in the complicated passage with a strong 3-D curvature, one-coefficient dynamic Sub-Grid-Scale （SGS） stress model was used in this article. The simulations show that the strong wakes in the inflow lead to a flow separation at the leading zone of the passage, and to form a primary vortex in the span-wise direction. The primary span-wise vortex evolves and splits into smaller vortex pairs due to the constraint of no-slip wall condition, which triggers losing stability of the flow in the passage. The computed pressures on the pressure and suction sides agree with the measured data for a working test turbine model.展开更多
An experimental and analytical investigation on the aerodynamic characteristics of a helicopter scissors tail rotor has been made. The experiments are carried out on a model rotor rig and the variations of the rotor t...An experimental and analytical investigation on the aerodynamic characteristics of a helicopter scissors tail rotor has been made. The experiments are carried out on a model rotor rig and the variations of the rotor thrust and torque with scissors angles are investigated. The effects of two different configurations, i.e., Configuration L in which the lower blade is in front of the upper blade and Configuration U in which the upper blade is in front of the lower blade, on rotor performance are compared. The experimental results have shown that the thrust for Configuration L is greater than that for Configuration U, and the strong blade-vortex interaction may occur at some scissors angles. A free-wake analytical model is then developed for predicting the aerodynamic characteristics of a scissors tail rotor and validated by numerical examples. By using the model, the blade induced velocity, lift distribution and tip vortex displacement of the scissors rotor are calculated. Based upon the calculations, the variations of the thrust with scissors angles in the experiments are analyzed and the strong blade-vortex interaction occurring in the experiments is explained. Finally, several conclusions are presented.展开更多
An iterative and full-coupled rotor/fuselage aerodynamic interaction analytical method is developed based upon the rotor free-wake model and the 3-D fuselage panel model. A close vortex/ surface interaction model usin...An iterative and full-coupled rotor/fuselage aerodynamic interaction analytical method is developed based upon the rotor free-wake model and the 3-D fuselage panel model. A close vortex/ surface interaction model using the Analytical/Numerical Matching (ANM) was adopted in the method in order to simulate effectively the unsteady close interaction between the rotor tip-vortex and fuselage surface. By the analytical method, the unsteady and steady pressure distribution on the fuselage surface, and the unsteady lift and pitching moment of the fuselage in a rotor interaction environment were calculated for different advance ratios. It is shown that the unsteady aerodynamic loads of the fuselage due to the rotor interaction have the same periodic characteristics as the rotor. The comparisons between the present close vortex/surface interaction model and a previous model, which simply excludes vortex filaments inside the fuselage, were also made and the advantages of the former over the latter were demonstrated in improving unsteady close interaction calculations.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50579025 and 90210005 ).
文摘Turbulent flow in a 3-D blade passage of a Francis hydro turbine was simulated with the Large Eddy Simulation （LES） to investigate the spatial and temporal distributions of the turbulence when strongly distorted wakes in the inflow sweep over the passage, In a suitable consideration of the energy exchanging mechanism between the large and small scales in the complicated passage with a strong 3-D curvature, one-coefficient dynamic Sub-Grid-Scale （SGS） stress model was used in this article. The simulations show that the strong wakes in the inflow lead to a flow separation at the leading zone of the passage, and to form a primary vortex in the span-wise direction. The primary span-wise vortex evolves and splits into smaller vortex pairs due to the constraint of no-slip wall condition, which triggers losing stability of the flow in the passage. The computed pressures on the pressure and suction sides agree with the measured data for a working test turbine model.
文摘An experimental and analytical investigation on the aerodynamic characteristics of a helicopter scissors tail rotor has been made. The experiments are carried out on a model rotor rig and the variations of the rotor thrust and torque with scissors angles are investigated. The effects of two different configurations, i.e., Configuration L in which the lower blade is in front of the upper blade and Configuration U in which the upper blade is in front of the lower blade, on rotor performance are compared. The experimental results have shown that the thrust for Configuration L is greater than that for Configuration U, and the strong blade-vortex interaction may occur at some scissors angles. A free-wake analytical model is then developed for predicting the aerodynamic characteristics of a scissors tail rotor and validated by numerical examples. By using the model, the blade induced velocity, lift distribution and tip vortex displacement of the scissors rotor are calculated. Based upon the calculations, the variations of the thrust with scissors angles in the experiments are analyzed and the strong blade-vortex interaction occurring in the experiments is explained. Finally, several conclusions are presented.
文摘An iterative and full-coupled rotor/fuselage aerodynamic interaction analytical method is developed based upon the rotor free-wake model and the 3-D fuselage panel model. A close vortex/ surface interaction model using the Analytical/Numerical Matching (ANM) was adopted in the method in order to simulate effectively the unsteady close interaction between the rotor tip-vortex and fuselage surface. By the analytical method, the unsteady and steady pressure distribution on the fuselage surface, and the unsteady lift and pitching moment of the fuselage in a rotor interaction environment were calculated for different advance ratios. It is shown that the unsteady aerodynamic loads of the fuselage due to the rotor interaction have the same periodic characteristics as the rotor. The comparisons between the present close vortex/surface interaction model and a previous model, which simply excludes vortex filaments inside the fuselage, were also made and the advantages of the former over the latter were demonstrated in improving unsteady close interaction calculations.
