David liang
Active Member
Hi all,
I have been considering how birds and insects fly with flapping wings.
These days I have some new thoughts about the flapping wing flight principle.
My idea is very different from the conventional aerodynamic theory for airplanes.
What do you think about my idea?
Any comments will be much appreciated.
Thank you in advance.
Best Regards,
David Liang
*************************************
New Aerodynamic Theory: Drag-based Flyers
The conventional aerodynamic theory for airplanes cannot explain the force of lift for flapping wings. I put forward a new aerodynamic theory that can explain the flapping wing flight of insects and birds very well.
First, to cite a reference here.
Airflow over any object creates two types of aerodynamic forces: the drag force, in the direction of the airflow, and the lift force, perpendicular to the airflow. According to the conventional aerodynamic theory, a flyer can fly by using the aerodynamic lift force, but the aerodynamic drag force hinders flying.
I put forward a new aerodynamic theory. According to the new theory, a flyer can also fly by using the aerodynamic drag force.
To explain the new theory, the windturbines are good examples to understand how a flyer can use the aerodynamic drag force to fly. It is because that the principle of windturbines is the inverse principle of flyers.
It is well known that windturbines can be classified into two types based on their working principles: the lift-based windturbines and the drag-based windturbines. The blades of lift-based windturbines are rotated by the aerodynamic lift force; the blades of drag-based windturbines are rotated by the aerodynamic drag force.
Fig.1 is a comparison of a helicopter and a conventional lift-based windturbine. The helicopter and the conventional lift-based windturbine both work based on the aerodynamic lift force; their working principle is the same.
Fig.2 shows the working principle of a drag-based windturbine using cup blades. The drag force on the cup moving forward is FF; the drag force on the cup moving backward is FB.
The difference between the FB and the FF creates a net aerodynamic force, rotating the blades. The rotating force Frotating can be written as:
Frotating =FB - FF
For the sake of comparison with the drag-based windturbine using cup blades, we can assume a drag-based flyer using cup wings.
Fig.3 shows a diagram of the drag-based flyer with two cup wings. The cup wing is connected to the body by a horizontal axis. The flyer flaps both the left and right cup wings with an up-and-down motion (reciprocating motion).
Fig.4 shows the working principle of the drag-based flyer with two cup wings. The drag force on the cup moving upward is FU; the drag force on the cup moving downward is FD.
The difference between the FD and the FU creates a net aerodynamic force, pointing upward. This force is the lift force Flift.
Flift =FD - FU
Fig. 5 is a comparison of a drag-based windturbine with two cup blades, and a drag-based flyer with two cup wings. Both of them work based on the aerodynamic drag force; their working principle is the same.
Theoretically, the drag-based flyer using cup wings can fly. To test if it will fly or not, I built a prototype of the drag-based flyer. Fig.6 is a picture of the drag-based prototype flyer.
Fig.7 is a video clip to show the test flight of the drag-based prototype flyer. (This video clip can be seen at: https://youtu.be/quaKRoFILtw).
In the test flight, the prototype flyer can get off the ground vertically. The result of the test flight validates that a flyer can fly by using the aerodynamic drag force.
[video=youtube_share;quaKRoFILtw]https://youtu.be/quaKRoFILtw[/video]
I also formulate a ‘flapping-wing flight formula’ based on the flapping wing flight theory.
Where, f is the wing flapping frequency of the flyer, WS is the wing load of the flyer, S is the wingspan of the flyer, and k is a constant.
Equation (3) can be called ‘flapping-wing flight formula’, because it describes the relationship between the wing’s static character (wing dimension, i.e. wing span and wing load) and the wing’s dynamic character (wing flapping frequency).
Here uses some realistic data to test the ‘flapping-wing flight formula’.
According to the ‘flapping-wing flight formula’, i.e. Equation (3), it can be predicted that the graph of the f value versus the
value will be a straight line with slope k. Fig.8 shows the graph of the f value vs. the value. This graph agrees very well with the prediction. So the result shows that the ‘flapping-wing flight formula’ is correct.
Based on the new aerodynamic theory, it can be concluded that a flyer can fly by using either the aerodynamic lifts force or the aerodynamic drag force.
The relationship among aerodynamic forces, windturbines and flyers can be described as follows:
1. There are two types of aerodynamic forces: the lift force and the drag force.
2. Windturbines have two types: the lift-based windturbines and the drag-based windturbines.
3. Flyers have two types: the lift-based flyers and the drag-based flyers.
Fig.9 shows the relationship among aerodynamic forces, windturbines and flyers.
For more details about the new theory, please see my blog:
http://linaircraft.blogspot.com/.
‘New Aerodynamic Theory: Drag-based Flyers’:
http://linaircraft.blogspot.jp/2016/12/newaerodynamic-theory-drag-based-flyers.html
‘Flapping Wing Flight Principle’:
http://linaircraft.blogspot.jp/2016/11/ornithopter-principles-and-designs_22.html
‘How to design ornithopters’:
http://linaircraft.blogspot.jp/2016/11/ornithopter-principles-and-designs-2.html
I have been considering how birds and insects fly with flapping wings.
These days I have some new thoughts about the flapping wing flight principle.
My idea is very different from the conventional aerodynamic theory for airplanes.
What do you think about my idea?
Any comments will be much appreciated.
Thank you in advance.
Best Regards,
David Liang
*************************************
New Aerodynamic Theory: Drag-based Flyers
The conventional aerodynamic theory for airplanes cannot explain the force of lift for flapping wings. I put forward a new aerodynamic theory that can explain the flapping wing flight of insects and birds very well.
First, to cite a reference here.
Airflow over any object creates two types of aerodynamic forces: the drag force, in the direction of the airflow, and the lift force, perpendicular to the airflow. According to the conventional aerodynamic theory, a flyer can fly by using the aerodynamic lift force, but the aerodynamic drag force hinders flying.
I put forward a new aerodynamic theory. According to the new theory, a flyer can also fly by using the aerodynamic drag force.
To explain the new theory, the windturbines are good examples to understand how a flyer can use the aerodynamic drag force to fly. It is because that the principle of windturbines is the inverse principle of flyers.
It is well known that windturbines can be classified into two types based on their working principles: the lift-based windturbines and the drag-based windturbines. The blades of lift-based windturbines are rotated by the aerodynamic lift force; the blades of drag-based windturbines are rotated by the aerodynamic drag force.
Fig.1 is a comparison of a helicopter and a conventional lift-based windturbine. The helicopter and the conventional lift-based windturbine both work based on the aerodynamic lift force; their working principle is the same.
Fig.2 shows the working principle of a drag-based windturbine using cup blades. The drag force on the cup moving forward is FF; the drag force on the cup moving backward is FB.
The difference between the FB and the FF creates a net aerodynamic force, rotating the blades. The rotating force Frotating can be written as:
Frotating =FB - FF
For the sake of comparison with the drag-based windturbine using cup blades, we can assume a drag-based flyer using cup wings.
Fig.3 shows a diagram of the drag-based flyer with two cup wings. The cup wing is connected to the body by a horizontal axis. The flyer flaps both the left and right cup wings with an up-and-down motion (reciprocating motion).
Fig.4 shows the working principle of the drag-based flyer with two cup wings. The drag force on the cup moving upward is FU; the drag force on the cup moving downward is FD.
The difference between the FD and the FU creates a net aerodynamic force, pointing upward. This force is the lift force Flift.
Flift =FD - FU
Fig. 5 is a comparison of a drag-based windturbine with two cup blades, and a drag-based flyer with two cup wings. Both of them work based on the aerodynamic drag force; their working principle is the same.
Theoretically, the drag-based flyer using cup wings can fly. To test if it will fly or not, I built a prototype of the drag-based flyer. Fig.6 is a picture of the drag-based prototype flyer.
Fig.7 is a video clip to show the test flight of the drag-based prototype flyer. (This video clip can be seen at: https://youtu.be/quaKRoFILtw).
In the test flight, the prototype flyer can get off the ground vertically. The result of the test flight validates that a flyer can fly by using the aerodynamic drag force.
[video=youtube_share;quaKRoFILtw]https://youtu.be/quaKRoFILtw[/video]
I also formulate a ‘flapping-wing flight formula’ based on the flapping wing flight theory.
Where, f is the wing flapping frequency of the flyer, WS is the wing load of the flyer, S is the wingspan of the flyer, and k is a constant.
Equation (3) can be called ‘flapping-wing flight formula’, because it describes the relationship between the wing’s static character (wing dimension, i.e. wing span and wing load) and the wing’s dynamic character (wing flapping frequency).
Here uses some realistic data to test the ‘flapping-wing flight formula’.
According to the ‘flapping-wing flight formula’, i.e. Equation (3), it can be predicted that the graph of the f value versus the
value will be a straight line with slope k. Fig.8 shows the graph of the f value vs. the value. This graph agrees very well with the prediction. So the result shows that the ‘flapping-wing flight formula’ is correct.
Based on the new aerodynamic theory, it can be concluded that a flyer can fly by using either the aerodynamic lifts force or the aerodynamic drag force.
The relationship among aerodynamic forces, windturbines and flyers can be described as follows:
1. There are two types of aerodynamic forces: the lift force and the drag force.
2. Windturbines have two types: the lift-based windturbines and the drag-based windturbines.
3. Flyers have two types: the lift-based flyers and the drag-based flyers.
Fig.9 shows the relationship among aerodynamic forces, windturbines and flyers.
For more details about the new theory, please see my blog:
http://linaircraft.blogspot.com/.
‘New Aerodynamic Theory: Drag-based Flyers’:
http://linaircraft.blogspot.jp/2016/12/newaerodynamic-theory-drag-based-flyers.html
‘Flapping Wing Flight Principle’:
http://linaircraft.blogspot.jp/2016/11/ornithopter-principles-and-designs_22.html
‘How to design ornithopters’:
http://linaircraft.blogspot.jp/2016/11/ornithopter-principles-and-designs-2.html
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