CN113591354B - Bionic flapping wing aircraft flexible flapping wing aerodynamic characteristic analysis method, computer equipment and storage medium - Google Patents
Bionic flapping wing aircraft flexible flapping wing aerodynamic characteristic analysis method, computer equipment and storage medium Download PDFInfo
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Abstract
The invention belongs to the technical field of aerodynamic characteristic analysis of aircrafts, and particularly relates to a method for analyzing the aerodynamic characteristics of flexible flapping wings of a bionic flapping wing aircraft, which comprises the following steps: designing a motion rule of the flapping wings; calculating aerodynamic force generated by the movement of the flapping wings; calculating the flexible deformation characteristic of the flapping wing under the aerodynamic action by utilizing the lift force and the thrust force; the flapping angle and the torsion angle of the primary flapping wing are corrected by utilizing the flexible deformation characteristics, so that the aerodynamic characteristics of the flapping wing flexible deformation effect are calculated and considered. The method can effectively analyze the flexible deformation of the flapping wings of the bionic flapping wing aircraft in the flying process, thereby calculating the aerodynamic characteristics of the flapping wing aircraft considering the flexible deformation effect, establishing a foundation for modeling the dynamic characteristics of the flapping wing aircraft and designing a controller, simplifying the aerodynamic characteristic analysis method for the problem of the flexible deformation of the flapping wings, meeting the precision requirement of the flapping wing aircraft considering the flexible deformation of the flapping wings, and providing a new thought and technical approach for the future analysis of the flexible aerodynamic characteristics of the flapping wings.
Description
Technical Field
The invention belongs to the technical field of aerodynamic characteristic analysis of aircrafts, and particularly relates to a method for analyzing the aerodynamic characteristics of flexible flapping wings of a bionic flapping wing aircraft, computer equipment and a storage medium.
Background
From the beginning of the last century to the present, the aviation technology has been rapidly developed for over 100 years, and various aircrafts have been developed, which far surpass the natural flying creatures in the aspects of flying speed, internal space, transportation bearing capacity and the like. However, the artificial aircraft cannot match the flying biological phase in nature in the above aspects under the same physical scale. Flying organisms in the nature select flapping wings as a flying propulsion mode after billions of years of evolution, and have incomparable excellent flying performance compared with an artificial aircraft. The flapping wing aircraft is a novel aircraft which appears in the last 30 years and simulates the shape, structure and flying mode of birds and flying insects. The flapping wing air vehicle is characterized in that a main body part of the flapping wing air vehicle comprises a flapping wing capable of moving in multiple degrees of freedom, and required lift force and thrust force are generated through the movement of the flapping wing. Flapping wing flight is the most common flight mode for flying organisms in nature, has higher biological rationality, flexible flight control and high pneumatic efficiency, and has more obvious advantages under the microminiature scale. The prior flapping wing air vehicle can be divided into a bird-imitating flapping wing air vehicle and an insect-imitating flapping wing air vehicle according to different flapping modes. The bird-imitating ornithopter and the insect-imitating ornithopter mainly differ in three aspects of flapping motion, flapping frequency and direction of a flapping surface of the flapping wings. The flapping wing air vehicle has similar flying mode to birds, and can generate flexible flying thrust and lift force through the movement of the flapping wings, so that the aerodynamic efficiency of the flapping wing air vehicle is much higher than that of a normal fixed wing air vehicle.
Li xi Ji researches the aerodynamic characteristics of the flapping wings and the empennage of a multi-section bionic flapping wing aircraft in the document 'multi-section bionic flapping wing aircraft flexible wing and empennage aerodynamic analysis', analyzes the aerodynamic change condition generated by the motion of the flapping wings under different parameter combinations, and provides a reference basis for the research on the aerodynamic characteristics of the flapping wing aircraft; the stroke ratio influence factor, the chord direction torsion function and the spread direction torsion function are introduced into an original constant-speed motion flapping wing model in the literature 'research on aerodynamic characteristics of flexible flapping wings', and the comparison simulation result shows that the aerodynamic characteristics of the flapping wings can be improved by the flexible change of the flapping wings; huminglan analyzes the action of inertia force of wings with different masses in the wing inertia force analysis of the imitation kun flapping wing aircraft, contrasts and analyzes the change condition of aerodynamic force generated by flapping wings under the condition of considering the inertia force or not, and provides a foundation for multi-body dynamics modeling.
In summary, the main problems in the analysis of aerodynamic characteristics of flapping wing aircraft are: the degree of deformation of the flapping wings cannot be quantitatively described; the influence of the flexible deformation effect of the flapping wings on the aerodynamic characteristics of the flapping wings is not considered; the time consumption for calculating the flexible deformation effect of the flapping wing is long, and the real-time requirement of control cannot be met.
Disclosure of Invention
The invention aims to provide a method for analyzing the aerodynamic characteristics of a flexible flapping wing of a bionic flapping wing aircraft, computer equipment and a storage medium, and solves the main problems in the aspect of aerodynamic characteristic analysis of the flapping wing aircraft at present.
The invention is realized by the following technical scheme:
a bionic flapping wing aircraft flexible flapping wing aerodynamic characteristic analysis method takes a flapping wing aircraft with a double-section wing structure as a research object, a flapping wing directly connected with a fuselage is called a secondary flapping wing, and a non-directly connected section is a primary flapping wing, and comprises the following steps:
s1, designing a motion rule of a flapping wing:
establishing a flapping law of the flapping wings in the flapping process to obtain a flapping angle of a primary flapping wing at the current moment in the flapping process;
establishing a flapping wing torsion rule in the flapping process to obtain a torsion angle of a primary flapping wing at the current moment in the flapping process;
s2, calculating aerodynamic force generated by flapping wing movement:
obtaining aerodynamic force generated by the flapping wings moving in the state at a certain moment according to the wind speed and the aerodynamic coefficient of the surface element relative to the incoming flow;
converting the aerodynamic force on each surface element to a flapping wing coordinate system to obtain a lift force parallel to the direction of the flapping wing coordinate system and a thrust force along the direction of the flapping wing coordinate system, and obtaining the lift force and the thrust force generated by the movement of the whole flapping wing plane through the integration of each surface element on the flapping wing plane;
s3: calculating the flexible deformation characteristic of the flapping wing under the aerodynamic action by utilizing the lift force and the thrust force;
s4: and correcting the flapping angle and the torsion angle of the primary flapping wing by utilizing the flexible deformation characteristic, thereby calculating the aerodynamic characteristics considering the flexible deformation effect of the flapping wing.
Further, in S1, the flapping process comprises an upper flapping and a lower flapping, and a flapping law of a flapping wing in the lower flapping process is established to obtain a flapping angle of a secondary flapping wing at the current moment and a flapping angle of a primary flapping wing at the current moment in the lower flapping process; the method comprises the following specific steps:
in the lower flapping process, the flapping angle of the secondary flapping wing at the current moment is as follows:
β s ＝β si -A βs +A βs cos(2πf d T)；
the flapping angle of the primary flapping wing at the current moment is as follows:
β p ＝β s +β pi
wherein, beta s The flapping angle of the secondary flapping wing at the current moment; beta is a si Is the initial flapping angle of the secondary flapping wing; a. The βs The flapping amplitude of the secondary flapping wing is obtained; beta is a beta p The flapping angle of the primary flapping wing at the current moment; beta is a pi Is the initial flapping angle of the primary flapping wing; f. of d The flapping frequency of the lower flapping process; and T represents the corresponding time of the current time in a single flapping cycle.
Further, in S1, the flapping process comprises upper flapping and lower flapping, and a flapping wing torsion rule in the lower flapping process is established to obtain a torsion angle of a primary flapping wing at the current moment and a torsion angle of a secondary flapping wing at the current moment in the lower flapping process; the method comprises the following specific steps:
in the lower flapping process, the torsion angle of the secondary flapping wing at the current moment is theta s The torsion angle of the primary flapping wing at the current moment is theta p The moment of changing the torsion angle is e p ；
When T is more than or equal to 0 and less than or equal to e p The calculation formula is as follows:
when in use
The calculation formula is as follows:
θ s ＝θ sd ；
θ p ＝θ pd ；
when the temperature is higher than the set temperature
The calculation formula is as follows:
wherein the content of the first and second substances,
wherein, theta sd The torsion angle amplitude of the secondary flapping wing in the lower flapping stage; theta.theta. su The torsion angle amplitude of the secondary flapping wing in the upper flapping stage; theta.theta. pd The torsion angle amplitude of the primary flapping wing at the lower flapping stage; theta.theta. pu The amplitude of the torsion angle of the primary flapping wing in the upper flapping stage; t represents the corresponding time of the current time in a single flapping cycle.
Further, in S1, the flapping process comprises upper flapping and lower flapping, and a flapping law of a flapping wing in the upper flapping process is established to obtain a flapping angle of a secondary flapping wing at the current moment and a flapping angle of a primary flapping wing at the current moment in the upper flapping process; the method specifically comprises the following steps:
in the upper flapping process, the flapping angle of the secondary flapping wing at the current moment is as follows:
the calculation formula of the flapping angle of the primary flapping wing at the current moment is as follows:
in the formula: beta is a beta s The flapping angle of the secondary flapping wing at the current moment; beta is a si As the initial stage of the secondary flapping wingFlapping angle; a. The βs The flapping amplitude of the secondary flapping wing; beta is a beta p The flapping angle of the primary flapping wing at the current moment; beta is a beta pi Is the initial flapping angle of the primary flapping wing; and T represents the corresponding time of the current time in a single flapping cycle.
Further, in S1, the flapping process comprises upper flapping and lower flapping, and a flapping wing torsion rule in the upper flapping process is established to obtain a torsion angle of a primary flapping wing at the current moment and a torsion angle of a secondary flapping wing at the current moment in the upper flapping process; the method specifically comprises the following steps:
in the upward flapping process, the torsion angle of the primary flapping wing at the current moment is theta s The torsion angle of the secondary flapping wing at the current moment is theta p ；
When in use
The calculation formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,
when the temperature is higher than the set temperature
The calculation formula is as follows:
θ s ＝θ su ；
θ p ＝θ sp ；
when (P-e) p ) When T is less than or equal to P, the calculation formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,
in the formula: theta sd The torsion angle amplitude of the secondary flapping wing in the lower flapping stage; theta su The torsion angle amplitude of the secondary flapping wing in the upper flapping stage; theta pd The torsion angle amplitude of the primary flapping wing at the lower flapping stage; theta pu Is the torsion angle amplitude of the primary flapping wing in the upper flapping stage.
Further, in S2, the aerodynamic force generated by the flapping wing moving in the state at a certain time comprises a lifting force F vertical to the incoming flow direction N And a resistance F parallel to the direction of the incoming flow D ；
Wherein, C N ,C D Is the aerodynamic coefficient; v is the velocity of the bin relative to the incoming flow.
Further, S3 specifically is: determining the deformation degree of the primary flapping wing in the moving process by adopting a finite element calculation method, adding loads on the wing surface, calculating the average lift force generated by the movement of the primary flapping wing in the lower flapping process and the upper flapping process, regarding the lift force as uniformly distributed loads and loading the uniformly distributed loads on the plane of the primary flapping wing, wherein the calculation formula of the torsional deformation angle of any point in the plane of the flapping wing in two directions is as follows:
α flex (x,z,t)＝α tip (x/λ p ) 2 (z/l p ) 2 (32)
β flex (x,z,t)＝β tip (x/λ p ) 2 (z/l p ) 2 (33)
in the formula: alpha is alpha flex The torsional deformation angle of any point on the primary flapping wing plane around the front edge; beta is a beta flex The torsional deformation angle of any point on the primary flapping wing plane around the wing root; alpha (alpha) ("alpha") tip The torsional deformation angle of the wing tip of the primary flapping wing around the leading edge; beta is a beta tip The primary flapping wing is in a torsional deformation angle around the wing root; lambda p Is the chord length of the primary flapping wing; l p Is the spread length of the primary flapping wing.
Further, S4 specifically is: and (2) superposing the torsional deformation angle around the leading edge into the torsional angle of the primary flapping wing, superposing the torsional deformation angle around the wing root into the flapping angle of the primary flapping wing, and calculating the corrected flapping angle and torsional angle of the primary flapping wing by the following formula:
θ pflex ＝θ p +α flex
β pflex ＝β p +β flex
wherein, theta pflex Representing the corrected primary flapping wing twist angle, beta pflex Representing the corrected primary flapping angle, α flex Representing the torsional deformation angle, beta, around the leading edge flex Representing the torsional deformation angle, theta, about the root of the wing p Is the torsion angle, beta, of the primary flapping wing p Is the flapping angle of the primary flapping wing.
The invention also discloses computer equipment which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, and is characterized in that the processor realizes the steps of the bionic flapping wing aircraft flexible flapping wing aerodynamic characteristic analysis method when executing the computer program.
The invention also discloses a computer readable storage medium, which stores a computer program, and is characterized in that the computer program is executed by a processor to realize the steps of the bionic flapping wing aircraft flexible flapping wing aerodynamic characteristic analysis method.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a method for analyzing the aerodynamic characteristics of flexible flapping wings of a bionic flapping wing aircraft, which can effectively analyze the flexible deformation of the flapping wings of the bionic flapping wing aircraft in the flying process, thereby calculating the aerodynamic characteristics of the flapping wing aircraft considering the flexible deformation effect and establishing a foundation for modeling the dynamic characteristics of the flapping wing aircraft and designing a controller. The method simplifies the aerodynamic characteristic analysis method for the flapping wing flexible deformation problem, meets the precision requirement of the flapping wing air vehicle considering the flapping wing flexible deformation, and provides a new thought and technical approach for the future analysis of the flapping wing flexible aerodynamic characteristics.
Drawings
FIG. 1 is a schematic view of a flapping wing segment of a bionic flapping wing aircraft;
FIG. 2 is a view of the flapping wing coordinate system definition;
FIG. 3 is a view of the flapping wing motion angle definition; FIG. 3 (a) is a flapping angle, and FIG. 3 (b) is a torsion angle;
FIG. 4 is a simplified model diagram of an aerodynamic flapping wing model;
FIG. 5 is a diagram of aerodynamic changes in flapping motion without taking into account primary compliance deformation;
FIG. 6 is a schematic view of the flexible deformation of the flapping wings;
FIG. 7 is a diagram of aerodynamic changes of flapping wing motion, which is obtained by the method for analyzing aerodynamic characteristics of flexible flapping wings and takes primary flexible deformation into consideration.
Wherein, 1 is a secondary flapping wing, 2 is a primary flapping wing, and 3 is a leading edge.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
As shown in fig. 1, the bionic object of the bionic flapping wing aircraft used in the invention is young gold carving, so the studied flapping wing aircraft has a double-section wing structure, wherein the flapping wing directly connected with the aircraft body is called as a secondary flapping wing 1, and the non-directly connected section is a primary flapping wing 2.
As shown in fig. 2, the flapping wing coordinate system is defined by taking the right secondary flapping wing 1 as an example, and the flapping wing coordinate system is defined as follows: the original point is the connection point of the secondary flapping wing 1 and the fuselage; the x axis is parallel to the chord line direction of the flapping wings and points to the head of the fuselage to be positive; the y axis is vertical to the flapping wing plane and points upwards to be positive; the z-axis is perpendicular to the plane.
Fig. 3 is a view defining the flapping wing motion angle, and the present invention is illustrated by taking the right secondary flapping wing 1 as an example: angle of oscillation beta rs O of coordinate system of secondary flapping wing 1 on right side 3 z 3 Axis and fuselage coordinate system O 1 x 1 z 1 Angle between planes, when O 3 z 3 The axis is located at O 1 x 1 z 1 Beta when lying below the plane rs Positive and negative otherwise. Torsion angle theta rs O of the coordinate System of the right-hand secondary flapping wing 1 3 x 3 Axis and frame coordinate system
Angle between planes, when O 3 x 3 The axis is located at O 1 x 1 z 1 Theta when above the plane rs Positive and negative otherwise.
The invention regards the leading edges 3 and the wing roots of the secondary flapping wing 1 and the primary flapping wing 2 as rigid skeletons, so that the secondary flapping wing 1 does not generate flexible deformation in the moving process, and only the influence of the flexible deformation of the primary flapping wing 2 on the aerodynamic force generated by the flapping wing needs to be considered for this purpose.
On the basis of the premise, the invention provides a bionic flapping wing aircraft flexible flapping wing aerodynamic characteristic analysis method, which comprises the following steps:
1) Designing flapping wing motion law
Since the flapping wing aircraft mainly generates upward lift force and forward thrust force by flapping of the flapping wings, it is very important to design a proper motion law of the flapping wings. The motion rule of the flapping wing designed by the invention mainly comprises two motions: flapping and twisting.
The flapping motion is mainly divided into two processes of lower flapping and upper flapping, wherein the lower flapping process accounts for 60% of the whole flapping cycle, and the upper flapping process accounts for 40% of the whole flapping cycle. Let the average flapping frequency of the whole process be f.
The flapping frequency of the lower flapping process is:
the frequency of the flapping process is:
p represents an average flapping cycle, T represents the flight time, Q represents the number of flapping cycles experienced, and T represents the corresponding time of the current time in a single flapping cycle, then:
T＝t-Q·P (4)
in formula (3): floor is an integer function.
The following is an illustration of the process of pounding:
in the process of putting down
The flapping law of the middle flapping wing is as follows:
β s ＝β si -A βs +A βs cos(2πf d T) (5)
β p ＝β s +β pi (6)
in formulae (5) and (6): beta is a s The flapping angle/degree of the secondary flapping wing 1 at the current moment; beta is a si Is the initial flapping angle/° of the secondary flapping wing 1; a. The βs The flapping amplitude/° of the secondary flapping wing 1; beta is a p The flapping angle/degree of the primary flapping wing 2 at the current moment; beta is a beta pi Is the initial flapping angle/° of the primary flapping wing 2.
The torsion law of the wings in the flapping process is shown in formulas (7) to (13):
when T is more than or equal to 0 and less than or equal to e p When e is greater than p Represents the moment of changing the torsion angle;
when in use
When the utility model is used, the water is discharged,
θ s ＝θ sd (9)
θ p ＝θ pd (10)
when the temperature is higher than the set temperature
When the temperature of the water is higher than the set temperature,
in the formulae (11) to (12),
the following is an explanation of the process of the upper flapping:
in the process of putting on
The flapping law of the middle flapping wing is as follows:
in formulae (14) and (15): beta is a s The flapping angle/degree of the secondary flapping wing 1 at the current moment; beta is a si Is the initial flapping angle/° of the secondary flapping wing 1; a. The βs Is the flapping amplitude/° of the secondary flapping wing 1; a. The βp Is the flapping amplitude/° of the primary flapping wing 2; beta is a p The flapping angle/degree of the primary flapping wing 2 at the current moment; beta is a beta pi Is the initial flapping angle/° of the primary flapping wing 2.
The torsion law of the flapping wing in the flapping process is shown in formulas (16) to (23):
when the temperature is higher than the set temperature
When the utility model is used, the water is discharged,
in the formulae (16) to (17),
when the temperature is higher than the set temperature
When the temperature of the water is higher than the set temperature,
θ s ＝θ su (19)
θ p ＝θ sp (20)
when (P-e) p ) When T is less than or equal to P,
in formulae (7) to (23): theta s The torsion angle/° of the secondary flapping wing 1 at the current moment; theta.theta. p Is the torsion angle/° of the primary flapping wing 2 at the current moment; theta sd The torsion angle amplitude/° of the secondary flapping wing 1 in the lower flapping stage; theta su The torsion angle amplitude/degree of the secondary flapping wing 1 in the upper flapping stage is shown; theta pd The torsion angle amplitude/degree of the primary flapping wing 2 at the lower flapping stage; theta.theta. pu The torsion angle amplitude/° of the primary flapping wing 2 of the upper flapping stage.
2) Calculating aerodynamic forces generated by flapping wings
In the process of flapping under the flapping wing, the speed of each calculation surface element in the flapping wing relative to air consists of two parts: one part is the flying speed V of the flapping wing aircraft ∞ And the other part is the flapping speed Vwown at which the flapping wings face downwards. The velocity of the bin relative to the incoming flow is:
the calculated bin is then the included angle with respect to the airflow:
α att ＝α b +θ+arctan((V down cos(α b ))/(V ∞ +V down sin(α b )) (25)
wherein alpha is b Is the flight angle of attack of the fuselage; theta is the torsion angle of the primary flapping wing 2, and the latter half of equation (25) is the influence of the surface element flapping velocity on the angle of attack.
Therefore, the aerodynamic force generated by the flapping wings moving in this state at a certain time is as follows:
in formulae (26) and (27), C N ,C D The calculation formula of (2) is as follows:
C N ＝0.225+1.58sin(2.13α att -7.2) (28)
C D ＝1.92-1.55cos(2.04α att -9.82) (29)
in formulae (26) to (29): alpha is alpha tt Calculating the attack angle of the surface element; c N ,C D Is the aerodynamic coefficient; v is the velocity of the calculation bin relative to the incoming flow; f N Being lift perpendicular to the direction of incoming flow, F D Is the resistance parallel to the incoming flow direction. The aerodynamic force on each surface element is converted into the coordinate system of the flapping wing to obtain the coordinate system O parallel to the flapping wing 3 y 3 Directional lifting force F L And along the flapping wing coordinate system O 3 x 3 Thrust of direction F M . The lift force and the thrust force generated by the movement of the whole flapping wing plane are obtained by integrating all surface elements on the flapping wing plane and are respectively:
L＝∫∫F L ds (30)
M＝∫∫F M ds (31)
3) Taking into account the flexible deformation of the flapping wings
As the primary flapping wing 2 of the real birds has larger area than the secondary flapping wing 1 and has less supporting skeleton, the flapping wing of the real birds which generates torsional deformation in the flying process is mainly the primary flapping wing 2, and the secondary flapping wing 1 hardly generates torsional deformation.
Therefore, the invention only considers the flexible deformation effect of the primary flapping wing 2, and the front edge 3 and the wing root of the primary flapping wing 2 are considered to be rigid skeletons, so that the flexible deformation at the front edge 3 and the wing root is not considered. And determining the deformation degree of the primary flapping wing 2 in the motion process by adopting a finite element calculation method. Adding loads on the airfoil surface, calculating the average lift force generated by the movement of the primary flapping wing 2 in the lower flapping process and the upper flapping process, and taking the lift force as uniform load to be loaded on the plane of the primary flapping wing 2. The torsion angle of one point on the flapping wing plane along the spanwise direction and the chordwise direction is changed in a manner similar to a parabola, and the calculation formula of the torsion deformation angle of any point in the flapping wing plane in two directions is as follows:
α flex (x,z,t)＝α tip (x/λ p ) 2 (z/l p ) 2 (32)
β flex (x,z,t)＝β tip (x/λ p ) 2 (z/l p ) 2 (33)
in the formula: alpha (alpha) ("alpha") flex The torsional deflection angle/° around the leading edge 3 at any point on the plane of the primary flapping wing 2; beta is a flex The torsional deformation angle/degree of any point on the plane of the primary flapping wing 2 around the wing root; alpha (alpha) ("alpha") tip Is the twist deflection angle/° of the wing tip of the primary flapping wing 2 around the leading edge 3; beta is a tip The torsional deformation angle/degree of the primary flapping wing 2 around the wing root; lambda [ alpha ] p Is the chord length/m of the primary flapping wing 2; l p Is the span length/m of the primary flapping wing 2.
The flexible deformation of the flapping wings is periodically changed, wherein the change period is equal to the flapping period, but the phase is advanced by 1/4 period of the flapping angle. The flapping of the primary flapping wing 2 is divided into two phases: the primary flapping wings 2 of the first stage at a frequency f d At a lower stroke of 1/2 of the cycle, the second stage being at 2f u Flapping continues for one cycle. The expression of the torsional deformation angle of the wing tip is obtained as follows:
the first stage is as follows:
and a second stage:
in formulae (34) to (37): alpha is alpha max1 Is the first orderMaximum value of chord-wise deformation angle/° of the primary flapping wing; beta is a max1 Is the maximum value/° of the spanwise deformation angle of the primary flapping of the first stage; alpha (alpha) ("alpha") max2 The maximum value/° of the chord-wise deformation angle of the primary flapping wing in the second stage; beta is a max2 Is the maximum value/° of the spanwise deflection angle of the primary flapping of the second stage. The average lift force generated by the primary flapping wing in the lower flapping process is calculated to be 13.49N, and the average lift force generated by the primary flapping wing in the upper flapping stage is calculated to be 20.78N. And loading the result on the primary flapping wing plane as the uniform load of the finite element analysis, wherein the finite element calculation result is as follows: in the first flapping stage, the maximum deformation angle of the wing tip around the wing root is about-10.4 ° and the maximum deformation angle around the leading edge is about-15.8 °; in the second flapping phase, the maximum deflection angle of the tip about the root is about 16.71 ° and the maximum deflection angle about the leading edge is about 21.16 °.
4) Correction of motion law of flapping wings by using flexible deformation characteristics
In view of the flexible deformation of the primary flapping wings 2, the law of motion of the primary flapping wings 2 needs to be corrected. The torsional deformation angle around the leading edge 3 is superposed into the torsional angle of the primary flapping wing 2, the torsional deformation angle around the wing root is superposed into the flapping angle of the primary flapping wing 2, and the calculation formula of the flapping angle and the torsional angle of the corrected primary flapping wing 2 is as follows:
θ pflex ＝θ p +α flex (38)
β pflex ＝β p +β flex (39)
wherein, theta pflex Representing the corrected primary flapping wing twist angle, beta pflex Representing the corrected primary flapping angle, alpha flex Representing the torsional deflection angle, beta, about the leading edge 3 flex Representing the torsional deflection angle around the root.
The torsional deformation angle of the leading edge 3 and the torsional deformation angle of the wing root are obtained by formula (32) and formula (33).
FIG. 4 is a simplified aerodynamic model of flapping wings, which is an improved quasi-steady model adopted by the invention to disperse the flapping motion process into a series of time points, wherein the aerodynamic force generated by the flapping motion of each time point is equal to the aerodynamic force generated by the flapping motion of the flapping wings in the same attitude in a quasi-steady state in a translation manner.
FIG. 5 is a diagram of aerodynamic changes in flapping motion without regard to primary compliance deformation showing that lift and thrust are periodically varied, the lift having one peak and one valley during the flapping cycle, the thrust having two peaks and two valleys during the flapping cycle; the maximum value of the lift force occurs at the moment when the flapping angle is zero in the lower flapping process, and the minimum value occurs at the moment when the flapping angle is zero in the upper flapping process; the maximum value of the thrust occurs at the moment when the flapping angle is zero during the upper and lower flapping, and the minimum value occurs at the moment when the flapping angle is maximum and minimum.
Fig. 6 is a schematic view of the flexible deformation of the flapping wing, showing the primary flapping wing 2 undergoing torsional deformation in two directions, namely torsional deformation around the leading edge 3 and torsional deformation around the wing root, both torsional deformation angles being zero at the wing root and the leading edge 3, and both torsional deformation angles being at a maximum at the wing tip.
FIG. 7 is a view of aerodynamic changes of flapping wing movement considering primary flexible deformation, which shows that the flexible deformation effect of the flapping wing mainly has great influence on the lift force of the flapping wing in the lower flapping process and the thrust force of the flapping wing in the upper flapping process, and the changes are that in the lower flapping stage, the lift force is increased and the thrust force is almost unchanged; in the flapping stage, the lift force is almost unchanged, and the thrust force is increased.
The method for analyzing the aerodynamic characteristics of the flexible flapping wings of the bionic flapping wing aircraft can adopt the forms of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The method for analyzing the aerodynamic characteristics of the flexible flapping wings of the bionic flapping wing aircraft can be stored in a computer readable storage medium if the method is realized in the form of a software functional unit and is sold or used as an independent product. Based on such understanding, all or part of the flow of the method according to the embodiments of the present invention may also be implemented by a computer program, which may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. Computer-readable storage media, including both permanent and non-permanent, removable and non-removable media, may implement the information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. It should be noted that the computer readable medium may contain content that is subject to appropriate increase or decrease as required by legislation and patent practice in jurisdictions, for example, in some jurisdictions, computer readable media does not include electrical carrier signals and telecommunications signals as is required by legislation and patent practice. The computer storage medium may be any available medium or data storage device that can be accessed by a computer, including but not limited to magnetic memory (e.g., floppy disk, hard disk, magnetic tape, magneto-optical disk (MO), etc.), optical memory (e.g., CD, DVD, BD, HVD, etc.), and semiconductor memory (e.g., ROM, EPROM, EEPROM, nonvolatile memory (NANDFLASH), solid State Disk (SSD)), etc.
In an exemplary embodiment, there is also provided a computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the method for analyzing the aerodynamic properties of a flexible flapping wing of a bionic flapping wing aircraft when executing the computer program. The processor may be a Central Processing Unit (CPU), other general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, etc.
The above description is only a general example of the present invention, and does not limit the present invention in any way, although the present invention is illustrated by the general example, which not only provides a flexible deformation characteristic analysis and simplified calculation method of aerodynamic characteristics for flapping wing aircraft considering flexible deformation, but also can be easily generalized to the problem of aerodynamic characteristic analysis of other different aircraft. Therefore, those skilled in the art can easily make various changes and modifications to the disclosed methods and techniques without departing from the scope of the invention, and equivalent embodiments can be obtained. However, any simple modification, equivalent change and modification made to the above general embodiments or similar works according to the technical essence of the present invention will still fall within the scope of the technical solution of the present invention unless it departs from the content of the technical solution of the present invention.
Claims (10)
1. A bionic flapping wing aircraft flexible flapping wing aerodynamic characteristic analysis method is characterized in that a flapping wing aircraft with a double-section wing structure is used as a research object, a flapping wing directly connected with a fuselage is called as a secondary flapping wing (1), and a non-directly connected section is a primary flapping wing (2), and comprises the following steps:
s1, designing a motion rule of a flapping wing:
establishing a flapping law of the flapping wings in the flapping process to obtain a flapping angle of the primary flapping wing (2) at the current moment in the flapping process;
establishing a flapping wing torsion rule in the flapping process to obtain a torsion angle of the primary flapping wing (2) at the current moment in the flapping process;
s2, calculating aerodynamic force generated by flapping wing movement:
obtaining aerodynamic force generated by the flapping wings moving in the state at a certain moment according to the wind speed and the aerodynamic coefficient of the surface element relative to the incoming flow;
converting the aerodynamic force on each surface element to a flapping wing coordinate system to obtain a lift force parallel to the direction of the flapping wing coordinate system and a thrust force along the direction of the flapping wing coordinate system, and obtaining the lift force and the thrust force generated by the movement of the whole flapping wing plane through the integration of each surface element on the flapping wing plane;
s3: calculating the flexible deformation characteristic of the flapping wing under the aerodynamic action by utilizing the lift force and the thrust force;
s4: the flapping angle and the torsion angle of the primary flapping wing (2) are corrected by utilizing the flexible deformation characteristics, so that the aerodynamic characteristics of the flapping wing flexible deformation effect are calculated and considered.
2. The method for analyzing the aerodynamic characteristics of the flexible flapping wings of the bionic flapping wing aircraft according to claim 1, wherein in S1, the flapping process comprises an upper flapping and a lower flapping, and a flapping law of the flapping wings in the lower flapping process is established to obtain a flapping angle of the secondary flapping wing (1) at the current moment and a flapping angle of the primary flapping wing (2) at the current moment in the lower flapping process; the method specifically comprises the following steps:
in the lower flapping process, the flapping angle of the secondary flapping wing (1) at the current moment is as follows:
β s ＝β si -A βs +A βs cos(2πf d T)；
the flapping angle of the primary flapping wing (2) at the current moment is as follows:
β p ＝β s +β pi
wherein, beta s The flapping angle of the secondary flapping wing (1) at the current moment is; beta is a si Is the initial flapping angle of the secondary flapping wing (1); a. The βs Is the flapping amplitude of the secondary flapping wing (1); beta is a p Is the flapping angle of the primary flapping wing (2) at the current moment; beta is a beta pi Is the initial flapping angle of the primary flapping wing (2); f. of d The flapping frequency of the lower flapping process; and T represents the corresponding time of the current time in a single flapping cycle.
3. The method for analyzing the aerodynamic characteristics of the flexible flapping wings of the bionic flapping wing aircraft according to claim 1, wherein in S1, the flapping process comprises an upper flapping and a lower flapping, and a flapping wing torsion rule in the lower flapping process is established to obtain a torsion angle of a primary flapping wing (2) at the current moment and a torsion angle of a secondary flapping wing (1) at the current moment in the lower flapping process; the method specifically comprises the following steps:
in the lower flapping process, the torsion angle of the secondary flapping wing (1) at the current moment is theta s The torsion angle of the primary flapping wing (2) at the current moment is theta p Varying the angle of torsionAt the time e p ；
When T is more than or equal to 0 and less than or equal to e p The calculation formula is as follows:
when the temperature is higher than the set temperature
The calculation formula is as follows:
θ s ＝θ sd ；
θ p ＝θ pd ；
when the temperature is higher than the set temperature
The calculation formula is as follows:
wherein the content of the first and second substances,
wherein, theta sd The amplitude of the torsion angle of the secondary flapping wing (1) in the lower flapping stage; theta su The torsion angle amplitude of the secondary flapping wing (1) in the upper flapping stage is obtained; theta pd The torsion angle amplitude of the primary flapping wing (2) at the lower flapping stage; theta.theta. pu The amplitude of the torsion angle of the primary flapping wing (2) in the upper flapping stage; t represents the corresponding current moment in a single flapping cycleThe time of day.
4. The method for analyzing the aerodynamic characteristics of the flexible flapping wings of the bionic flapping wing aircraft according to claim 1, wherein in S1, the flapping process comprises an upper flapping and a lower flapping, and a flapping law of the flapping wings in the upper flapping process is established to obtain a flapping angle of a secondary flapping wing (1) at the current moment in the upper flapping process and a flapping angle of a primary flapping wing (2) at the current moment; the method specifically comprises the following steps:
in the upper flapping process, the flapping angle of the secondary flapping wing (1) at the current moment is as follows:
the calculation formula of the flapping angle of the primary flapping wing (2) at the current moment is as follows:
in the formula: beta is a beta s The flapping angle of the secondary flapping wing (1) at the current moment is; beta is a si Is the initial flapping angle of the secondary flapping wing (1); a. The βs Is the flapping amplitude of the secondary flapping wing (1); beta is a p The flapping angle of the primary flapping wing (2) at the current moment; beta is a pi Is the initial flapping angle of the primary flapping wing (2); t represents the corresponding time of the current time in a single flapping cycle.
5. The method for analyzing the aerodynamic characteristics of the flexible flapping wings of the bionic flapping wing aircraft according to claim 1, wherein in S1, the flapping process comprises an upper flapping and a lower flapping, and a flapping wing torsion rule in the upper flapping process is established to obtain a torsion angle of a primary flapping wing (2) at the current moment in the upper flapping process and a torsion angle of a secondary flapping wing (1) at the current moment; the method specifically comprises the following steps:
in the upward flapping process, the torsion angle of the primary flapping wing (2) at the current moment is theta s The torsion angle of the secondary flapping wing (1) at the current moment is theta p ；
When in use
The calculation formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,
when in use
The calculation formula is as follows:
θ s ＝θ su ；
θ p ＝θ sp ；
when (P-e) p ) When T is less than or equal to P, the calculation formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,
in the formula: theta.theta. sd The torsion angle amplitude of the secondary flapping wing (1) in the lower flapping stage is obtained; theta su The torsion angle amplitude of the secondary flapping wing (1) in the upper flapping stage is obtained; theta pd The torsion angle amplitude of the primary flapping wing (2) at the lower flapping stage; theta.theta. pu The amplitude of the torsion angle of the primary flapping wing (2) in the upper flapping stage.
6. The method for analyzing the aerodynamic characteristics of the flexible flapping wing of a bionic flapping wing aircraft according to claim 1, wherein in S2, the aerodynamic force generated by the flapping wing moving in the state at a certain moment comprises a lifting force F vertical to the incoming flow direction N And a resistance F parallel to the direction of the incoming flow D ；
Wherein, C N ,C D Is the aerodynamic coefficient; v is the velocity of the bin relative to the incoming flow.
7. The method for analyzing the aerodynamic characteristics of the flexible flapping wings of the bionic flapping wing aircraft according to claim 6, wherein S3 specifically comprises the following steps: determining the deformation degree of the primary flapping wing (2) in the moving process by adopting a finite element calculation method, adding load on the wing surface, calculating the average lift force generated by the movement of the primary flapping wing (2) in the lower flapping process and the upper flapping process, regarding the lift force as uniformly distributed load and loading the uniformly distributed load on the plane of the primary flapping wing (2), wherein the calculation formula of the torsional deformation angle of any point in the plane of the flapping wing in two directions is as follows:
α flex (x,z,t)＝α tip (x/λ p ) 2 (z/l p ) 2 (32)
β flex (x,z,t)＝β tip (x/λ p ) 2 (z/l p ) 2 (33)
in the formula: alpha is alpha flex The angle of torsional deformation of any point on the plane of the primary flapping wing (2) around the front edge (3); beta is a beta flex The wing root is wound at any point on the plane of the primary flapping wing (2)The torsional deformation angle of (a); alpha is alpha tip The torsional deformation angle of the wing tip of the primary flapping wing (2) around the leading edge (3); beta is a beta tip The primary flapping wing (2) is in a torsional deformation angle around the wing root; lambda p Is the chord length of the primary flapping wing (2); l. the p Is the expansion length of the primary flapping wing (2).
8. The method for analyzing the aerodynamic characteristics of the flexible flapping wings of the bionic flapping wing aircraft according to claim 7, wherein S4 specifically comprises: the torsional deformation angle around the leading edge (3) is superposed into the torsional angle of the primary flapping wing (2), the torsional deformation angle around the wing root is superposed into the flapping angle of the primary flapping wing (2), and the calculation formula of the flapping angle and the torsional angle of the corrected primary flapping wing (2) is as follows:
θ pflex ＝θ p +α flex
β pflex ＝β p +β flex
wherein, theta pflex Representing the corrected primary flapping wing twist angle, beta pflex Representing the corrected primary flapping angle, α flex Representing the torsional deformation angle, beta, around the leading edge (3) flex Representing the torsional deformation angle, theta, about the root of the wing p Is the torsion angle, beta, of the primary flapping wing (2) p Is the flapping angle of the primary flapping wing (2).
9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor when executing the computer program performs the steps of the method of analyzing the aerodynamic characteristics of the flexible flapping wings of a biomimetic flapping wing aircraft according to any one of claims 1 to 8.
10. A computer-readable storage medium, in which a computer program is stored, which, when being executed by a processor, carries out the steps of the method for analyzing the aerodynamic characteristics of a flexible flapping wing of a bionic flapping wing aircraft according to any one of claims 1 to 8.
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| CN111611652A (en) * | 2020-06-04 | 2020-09-01 | 电子科技大学 | Flapping wing aerodynamic characteristic analysis method based on active flexible deformation |
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| CN111611652A (en) * | 2020-06-04 | 2020-09-01 | 电子科技大学 | Flapping wing aerodynamic characteristic analysis method based on active flexible deformation |
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