Stabilizers and their control surfaces are vital components in maneuvering an airplane during flight. However, a shortcoming of stabilizers is that they require airstream or propeller wash for them to work properly. I...Stabilizers and their control surfaces are vital components in maneuvering an airplane during flight. However, a shortcoming of stabilizers is that they require airstream or propeller wash for them to work properly. In this work, we propose the concept of roto-stabilizer as viable substitution for conventional horizontal stabilizer. A key benefit of the proposed technique is its ability to exert powerful moment in the absence of forward airspeed or propeller wash. Proof of principle is demonstrated via computer simulations. Results reveal that new aerobatic maneuvers are made possible. Furthermore, when implemented in canard configuration, it is possible to achieve ultra-STOL and VTOL.展开更多
Based on the historical data over 15 years from fivecounties including Xiaoshan,Longyou,Pujiang,Wenling,and Huangyan,Zhejiang Province,a se-ries of forecasting models were established by stepwise regression.These mode...Based on the historical data over 15 years from fivecounties including Xiaoshan,Longyou,Pujiang,Wenling,and Huangyan,Zhejiang Province,a se-ries of forecasting models were established by stepwise regression.These models could be used to pre-dict the population size and the level of the main en-dangering generation of brown planthopper(BPH)on late-season rice.After eight years validation,73models were established from 469 ones as a series ofmodels used as long,medium,and short term fore-casting.展开更多
Distributed Electric Propulsion(DEP)aircraft use multiple electric motors to drive the propulsors,which gives potential benefits to aerodynamic-propulsion interaction.To investigate and quantify the aerodynamic-propul...Distributed Electric Propulsion(DEP)aircraft use multiple electric motors to drive the propulsors,which gives potential benefits to aerodynamic-propulsion interaction.To investigate and quantify the aerodynamic-propulsion interaction effect of the wing section,we built a DEP demonstrator with 24"high-lift"Electric Ducted Fans(EDFs)distributed along the wing’s trailing edge.This paper explores and compares the aero-propulsion coupling characteristics under various upstream speed,throttle,and EDF mounting surface deflection angles using a series of wind tunnel tests.We compare various lift-augmentation power conditions to the clean configuration without propulsion unit under the experiment condition of 15-25 m/s freestream flow and angles of attack from-4°to 16°.The comparison of computational results to the experimental results verifies the effectiveness of the computational fluid dynamic analysis method and the modeling method for the DEP configuration.The results show that the EDFs can produce significant lift increment and drag reduction simultaneously,which is accordant with the potential benefit of Boundary Layer Ingestion(BLI)at low airspeed.展开更多
Turbulent kinetic energy budgets are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The different terms are obtained in the vertical plane...Turbulent kinetic energy budgets are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The different terms are obtained in the vertical plane of symmetry by quadratic interpolation of the LDV （Laser Doppler Velocimetry） measurements, for a wall jet-to-boundary layer velocity ratio of 2. The results, which have relevance to flows encountered in powered-lift aircraft operating in ground effect, quantify the structure of the complex ground vortex flow. The analysis of turbulent energy equation terms using the measured data revealed that production by normal and shear stresses are both very important to the turbulent structure of the impact zone of the ground vortex. This is an indication that the modeling of turbulence of a ground vortex requires a good representation of the production by normal stresses which is most important in the collision zone.展开更多
文摘Stabilizers and their control surfaces are vital components in maneuvering an airplane during flight. However, a shortcoming of stabilizers is that they require airstream or propeller wash for them to work properly. In this work, we propose the concept of roto-stabilizer as viable substitution for conventional horizontal stabilizer. A key benefit of the proposed technique is its ability to exert powerful moment in the absence of forward airspeed or propeller wash. Proof of principle is demonstrated via computer simulations. Results reveal that new aerobatic maneuvers are made possible. Furthermore, when implemented in canard configuration, it is possible to achieve ultra-STOL and VTOL.
文摘Based on the historical data over 15 years from fivecounties including Xiaoshan,Longyou,Pujiang,Wenling,and Huangyan,Zhejiang Province,a se-ries of forecasting models were established by stepwise regression.These models could be used to pre-dict the population size and the level of the main en-dangering generation of brown planthopper(BPH)on late-season rice.After eight years validation,73models were established from 469 ones as a series ofmodels used as long,medium,and short term fore-casting.
基金supported by the National Natural Science Foundation of China(No.51877178)。
文摘Distributed Electric Propulsion(DEP)aircraft use multiple electric motors to drive the propulsors,which gives potential benefits to aerodynamic-propulsion interaction.To investigate and quantify the aerodynamic-propulsion interaction effect of the wing section,we built a DEP demonstrator with 24"high-lift"Electric Ducted Fans(EDFs)distributed along the wing’s trailing edge.This paper explores and compares the aero-propulsion coupling characteristics under various upstream speed,throttle,and EDF mounting surface deflection angles using a series of wind tunnel tests.We compare various lift-augmentation power conditions to the clean configuration without propulsion unit under the experiment condition of 15-25 m/s freestream flow and angles of attack from-4°to 16°.The comparison of computational results to the experimental results verifies the effectiveness of the computational fluid dynamic analysis method and the modeling method for the DEP configuration.The results show that the EDFs can produce significant lift increment and drag reduction simultaneously,which is accordant with the potential benefit of Boundary Layer Ingestion(BLI)at low airspeed.
文摘Turbulent kinetic energy budgets are presented for a highly curved flow generated by the collision of plane wall turbulent jet with a low-velocity boundary layer. The different terms are obtained in the vertical plane of symmetry by quadratic interpolation of the LDV （Laser Doppler Velocimetry） measurements, for a wall jet-to-boundary layer velocity ratio of 2. The results, which have relevance to flows encountered in powered-lift aircraft operating in ground effect, quantify the structure of the complex ground vortex flow. The analysis of turbulent energy equation terms using the measured data revealed that production by normal and shear stresses are both very important to the turbulent structure of the impact zone of the ground vortex. This is an indication that the modeling of turbulence of a ground vortex requires a good representation of the production by normal stresses which is most important in the collision zone.
