This study investigates the aerodynamic characteristics of a low-Reynolds-number airfoil at high angles of attack(AoA)from 0°to 90°,focusing on their relevance for micro and unmanned aerial vehicle(MAV/UAV)a...This study investigates the aerodynamic characteristics of a low-Reynolds-number airfoil at high angles of attack(AoA)from 0°to 90°,focusing on their relevance for micro and unmanned aerial vehicle(MAV/UAV)applications.Simulations are conducted using the k-ωshear stress transport(SST)turbulence model using ANSYS Fluent software.Among the key findings is that the lift coefficient CL increases from 1.2981 at 0°AoA to a peak of 2.034 at 11°before decreasing to 1.51 at 90°,indicating initial lift improvement followed by a reduction due to potential flow separation or stall.The drag coefficient CD increases from 0.0222 at 0°AoA to a peak of 0.3572 at 12°,and then decreases to 0.0467 at 90°,indicating initially increasing turbulence and separation,followed by stabilization in the flow regime.The lift-to-drag ratio L/D reaches its maximum of 32.334 at 90°AoA,highlighting improved aerodynamic efficiency at higher AoAs despite increased drag.The skin friction coefficient Cf shows a maximum of 0.046918 at the leading edge at 30°AoA and 0.0394262 at the trailing edge at 90°,indicating critical points of frictional drag.Additionally,the turbulence viscosity ratio at the LE peaks at 0.5586 at 30°AoA and drops to 0.004 at 90°,while it increases at the trailing edge,reaching 0.0394262 at 90°,showing heightened turbulence effects at high AoAs.The present numerical study,however,determines the lift coefficient to be 2.00.This yields a maximum percentage variation of 11.5%compared with the value in the literature.These results provide a comprehensive overview of how high-AoA conditions impact aerodynamic performance,offering valuable insights for optimizing airfoil design and improving MAV/UAV efficiency.展开更多
Benefiting from the inherent superiorities in flexibility and mobility,the use of unmanned aerial vehicles(UAVs)as flying base stations for wireless coverage has been of significant interest,especially for rescue serv...Benefiting from the inherent superiorities in flexibility and mobility,the use of unmanned aerial vehicles(UAVs)as flying base stations for wireless coverage has been of significant interest,especially for rescue services.This work concerns the reliable emergency communication based on commercial micro-sized UAVs due to their high availability and low cost.To decrease the weight overloads and to improve the power efficiency,a UAV body conformal and omnidirectional antenna is first presented based on the characteristic mode analysis.To extend the wireless coverage and to improve the communication quality of the UAV network,a UAV flight formation is then proposed and analyzed.In addition,the propagation analyses for the proposed UAV transmitter designs are performed in a realistic hilly canyon region.Simulations and comparisons are presented to demonstrate the effectiveness of the proposed designs in emergency communications and performance enhancement through the UAV flight formation.展开更多
文摘This study investigates the aerodynamic characteristics of a low-Reynolds-number airfoil at high angles of attack(AoA)from 0°to 90°,focusing on their relevance for micro and unmanned aerial vehicle(MAV/UAV)applications.Simulations are conducted using the k-ωshear stress transport(SST)turbulence model using ANSYS Fluent software.Among the key findings is that the lift coefficient CL increases from 1.2981 at 0°AoA to a peak of 2.034 at 11°before decreasing to 1.51 at 90°,indicating initial lift improvement followed by a reduction due to potential flow separation or stall.The drag coefficient CD increases from 0.0222 at 0°AoA to a peak of 0.3572 at 12°,and then decreases to 0.0467 at 90°,indicating initially increasing turbulence and separation,followed by stabilization in the flow regime.The lift-to-drag ratio L/D reaches its maximum of 32.334 at 90°AoA,highlighting improved aerodynamic efficiency at higher AoAs despite increased drag.The skin friction coefficient Cf shows a maximum of 0.046918 at the leading edge at 30°AoA and 0.0394262 at the trailing edge at 90°,indicating critical points of frictional drag.Additionally,the turbulence viscosity ratio at the LE peaks at 0.5586 at 30°AoA and drops to 0.004 at 90°,while it increases at the trailing edge,reaching 0.0394262 at 90°,showing heightened turbulence effects at high AoAs.The present numerical study,however,determines the lift coefficient to be 2.00.This yields a maximum percentage variation of 11.5%compared with the value in the literature.These results provide a comprehensive overview of how high-AoA conditions impact aerodynamic performance,offering valuable insights for optimizing airfoil design and improving MAV/UAV efficiency.
基金This work was supported in part by National Natural Science Foundation of China(NSFC)under Grant No.61901020the Open Research Fund from Shenzhen Research Institute of Big Data under Grant No.2019ORF01012.
文摘Benefiting from the inherent superiorities in flexibility and mobility,the use of unmanned aerial vehicles(UAVs)as flying base stations for wireless coverage has been of significant interest,especially for rescue services.This work concerns the reliable emergency communication based on commercial micro-sized UAVs due to their high availability and low cost.To decrease the weight overloads and to improve the power efficiency,a UAV body conformal and omnidirectional antenna is first presented based on the characteristic mode analysis.To extend the wireless coverage and to improve the communication quality of the UAV network,a UAV flight formation is then proposed and analyzed.In addition,the propagation analyses for the proposed UAV transmitter designs are performed in a realistic hilly canyon region.Simulations and comparisons are presented to demonstrate the effectiveness of the proposed designs in emergency communications and performance enhancement through the UAV flight formation.
