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Straight-level flight
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
One of the important parameters in a cruising flight is the lift-to-drag ratio. One of the objectives in aerodynamic design of an aircraft is to design an aircraft that produces the maximum lift with a minimum drag. In this regard, the lift-to-drag ratio plays a significant role in the aircraft design process. This design objective has several applications.
Feasibility of Adaptive Micro Air Vehicles
Published in Norman M. Wereley, Inderjit Chopra, Darryll J. Pines, Twelfth International Conference on Adaptive Structures and Technologies, 2017
Felipe Bohorquez, Chris Cadou, Darryll Pines
Figures 6 thru 9 illustrate these geometric scaling relationships for small birds and how they compare to three current MAV designs. Although approximate, these scaling relationships illustrate that most MAV designs have shorter wingspans and lower aspect ratios than their biological counterparts, suggesting a higher maneuverability than the equivalent size bird. However, higher maneuverability for the same mass also implies higher bandwidth control for these systems. Another important property of winspan and aspect ratio is its connection to the aerodynamic properties of an aircraft. As the wingspan and aspect ratio increases, the lift to drag ratio also increases affecting the glide ratio of the aircraft. Thus, birds with long wingspans and high aspect ratios are more akin to dynamic soaring. Since most MAVs have short wingspans and low aspect ratios, one would not expect for these vehicles to have great glide or soaring properties. Finally, Figure 8 displays the average wing loading (N/m2) values for birds as a function of body mass. Specific birds are displayed by the ‘x’ symbol. The wing loading for three MAVs is also displayed in this figure with the ‘o’ symbol. Notice that the wing loading for MAVs is significantly higher than the equivalent size bird. This suggests that MAVs must fly faster in comparison to birds of comparable geometric size, aerodynamic properties and weight to stay aloft. To accomplish this goal MAVs must expend more power to overcome the induced aerodynamic drag. Another interesting aspect of nature is that the wing and aspect ratio for hummingbirds tends to be independent of body mass while their wingspan increases monotonically with mass. Figure 9 summarizes these geometric scaling laws for birds on a single chart and indicates that nature has figured out more efficient ways of achieving flight at low Reynolds number than humans.
Design and analysis of submerged tidal turbine
Published in International Journal of Ambient Energy, 2020
P. V. Arunraj, Tamanna Ali, Akrit Kumar, Veda Prakash, Nirajan Kashyap
Figures 11 and 12 depict Cl to Cd graph and Cl/Cd to angle of attack graph. For blades to be efficient it is very necessary to obtain higher lift-to-drag ratio (Figure 12). The lift-to-drag proportion is only the measure of lift created by the blades to the drag it cases by its development in the seawater. One of the main objectives or goals is to obtain a higher lift-to-drag ratio. From the above results, it can be concluded that the objective of obtaining a higher lift-to-drag ratio was successfully obtained.