2 Aerodynamics
97
Fig. 2.29 Theoretical adaptability based on the ideal flow around an airfoil
suitable for the flow characteristics of different local regions of airfoil flow,
as shown in Fig. 2.29.
A large number of wind tunnel tests show that the aerodynamic force
acting on the airfoil is related to the shape, size, and attitude of the airfoil.
In particular, the shape of the airfoil has an effect on the ratio of lift
to drag. With a good airfoil shape, the ratio of lift to drag produced is
large and the aerodynamic efficiency is high. That is to say, the resistance
required to lift a Newtonian gravity is small and the efficiency is good.
In aerodynamics, the optimization of the airfoil is specially discussed. In
principle, it is to seek the shape with the largest ratio of lift to drag (as
shown in Fig. 2.29). In today’s aircraft wing design, it is an eternal aerodynamic optimization problem to seek the shape with a large ratio of lift
to drag. For the airfoil of large civil aircraft, the designed ratio of lift to
drag can reach between 80 and 110.
2.3 Development and Influence Mechanism
of Boundary Layer Near Airfoil Surface
In the unbounded flow field, when an infinite cylinder rotating at a constant
speed reaches equilibrium, a resultant force perpendicular to the flow direction acts on the cylinder, which is called lift force. If the rotating cylinder is
regarded as the vortex core, the flow field in the vortex core is the vortex field
with equal vorticity, and the flow field outside the vortex core is the flow field
97
Fig. 2.29 Theoretical adaptability based on the ideal flow around an airfoil
suitable for the flow characteristics of different local regions of airfoil flow,
as shown in Fig. 2.29.
A large number of wind tunnel tests show that the aerodynamic force
acting on the airfoil is related to the shape, size, and attitude of the airfoil.
In particular, the shape of the airfoil has an effect on the ratio of lift
to drag. With a good airfoil shape, the ratio of lift to drag produced is
large and the aerodynamic efficiency is high. That is to say, the resistance
required to lift a Newtonian gravity is small and the efficiency is good.
In aerodynamics, the optimization of the airfoil is specially discussed. In
principle, it is to seek the shape with the largest ratio of lift to drag (as
shown in Fig. 2.29). In today’s aircraft wing design, it is an eternal aerodynamic optimization problem to seek the shape with a large ratio of lift
to drag. For the airfoil of large civil aircraft, the designed ratio of lift to
drag can reach between 80 and 110.
2.3 Development and Influence Mechanism
of Boundary Layer Near Airfoil Surface
In the unbounded flow field, when an infinite cylinder rotating at a constant
speed reaches equilibrium, a resultant force perpendicular to the flow direction acts on the cylinder, which is called lift force. If the rotating cylinder is
regarded as the vortex core, the flow field in the vortex core is the vortex field
with equal vorticity, and the flow field outside the vortex core is the flow field