9, b, as the height from the ground decreased, the
lift coefficient diminished to some small value due to the influences of the suction area developed on the lower surface of the wings.
The powered-lift, developed by researchers at the NASA Langley Research Center in the mid-1950s, gave the aircraft close to double the
lift coefficient of a conventional transport airframe by positioning the engines and flaps in a way that directed the exhaust downward.
Based on the averaged drag and
lift coefficient an AL model for the tower was implemented.
Thirdly, the maximum mean
lift coefficient as well as hovering efficiency is achieved when the wing has [[rho].sup.*] = 1750, which indicates that the flexible wing with [[rho].sup.*] = 1750 has better hovering performance than the other considered wing in this section.
Although the maximal
lift coefficient is low comparing to other conceptual studies [44], especially dedicated for the same purpose [16], the designed UAV has satisfactory parameters from the project aims point of view.
The
Lift Coefficient (Cl) is the lifting force and Drag Coefficient (Cd) is the drag or resistance force that generated by the airfoils are important role in designing wind turbine.
Table 1: Characteristic design Parameters Chord 0.4167 ft Lift Curve Slope 4.712 /rad Min
Lift Coefficient -1.1 Max
Lift Coefficient 1.1 Drag Coefficient Gain 0.9 Drag Coefficient Offset 0.9 Duct Moment Coefficient 0.8 Table 2: Mesh details Mesh type Hybrid mesh (tetra/prism) Global element size 0.04 Prism mesh 0.004 Prism mesh layers around duct 6 Total mesh elements 5,48,446 Mesh nodes 95,317 Table 3: Result Analysis L/D ratio for duct 3.686 L/uD ratio for ducted propeller 3.862
When the Reynolds numbers are 1000 and 30000, respectively, changing L/D = 0.5~2.0 to simulation can be found to reduce the drag coefficient,
lift coefficient, and vortex shedding frequency.
According to the time-averaged value of the calculated data, the relations between drag coefficient,
lift coefficient, and angle of attack are depicted in Figure 5.
