Method for optimizing propulsion performance of bionic flapping wing under multiple working conditions

Abstract

This invention discloses a method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions, relating to the fields of biomimetic fluid mechanics and propulsion technology. The method includes steps such as selecting the airfoil of the biomimetic flapping wing, setting the distance between the pitch axis and leading edge of the biomimetic flapping wing, setting the motion mode of the biomimetic flapping wing, adjusting the phase difference and pitch amplitude to match the motion mode of the biomimetic flapping wing under different operating conditions, setting the pitch frequency to be equal to the heave frequency, adjusting the pitch motion mode according to the pitch amplitude, and calculating the propulsion power coefficient and propulsion efficiency of the biomimetic flapping wing. This invention achieves precise control of different propulsion directions by optimizing the phase difference under different operating conditions; it determines the optimal frequency matching relationship to avoid propulsion performance degradation caused by frequency mismatch, ensuring stable and efficient operation of the flapping wing under all operating conditions; and it optimizes non-harmonic motion parameters for large pitch amplitudes, increasing propulsion efficiency to 24.10%, a 71% improvement compared to harmonic motion, significantly reducing energy loss.

Description

Technical Field

[0001] This invention relates to the fields of biomimetic fluid dynamics and propulsion technology, specifically to a method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions. Background Technology

[0002] With the development of renewable energy and underwater vehicle technology, biomimetic flapping wing-based propulsion systems have attracted widespread attention in fields such as fluid energy capture and underwater propulsion due to their environmentally friendly and efficient characteristics. The propulsion performance of flapping wings depends on the precise matching of motion parameters. Existing research mostly focuses on the parameter effects under a single harmonic motion mode, but has not systematically explored the phase difference and frequency difference between pitch and heave motions, as well as the synergistic effect mechanism of non-harmonic pitch motion on propulsion efficiency.

[0003] Current flapping-wing propulsion technologies often face challenges in balancing propulsion power and efficiency, as well as poor parameter adaptability under different operating conditions. For example, upstream propulsion is limited at small pitch amplitudes, while energy loss is significant at large pitch amplitudes, and the potential of non-harmonic motion is not fully exploited. These shortcomings limit the large-scale application of flapping-wing propulsion devices in engineering. Therefore, a control method is needed to achieve efficient propulsion under different operating conditions through multi-parameter collaborative optimization. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions. This method, based on practical engineering considerations, solves the problems of low propulsion efficiency and poor parameter adaptability of existing biomimetic flapping wing propellers by accurately matching pitch-heave motion parameters and optimizing non-harmonic motion modes.

[0005] To achieve the above-mentioned technical effects, the present invention is implemented through the following technical solution: A method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions includes the following steps: S1. Select the airfoil of the bionic flapping wing, connect the bionic flapping wing to the energy harvesting device through a torsion spring, and set the pitch axis and leading edge distance of the bionic flapping wing so that the bionic flapping wing can achieve coordinated heave and pitch movements. S2, Set the movement mode of the bionic flapping wing: Since the biomimetic flapping wing simultaneously performs heave and pitch motions, and its heave motion is driven by waves while its pitch motion is driven by external power, the equation of motion for the biomimetic flapping wing is as follows: (1) (2) In the formula, For the heave and pitch displacement of biomimetic flapping wings, For the heave amplitude, For heave frequency, The pitch angle, For pitch amplitude, For pitch frequency, Phase difference; S3. Adjust the phase difference and pitch amplitude to match the motion patterns of the bionic flapping wing under different operating conditions to improve the propulsion efficiency of the bionic flapping wing: S31. Adjustment of pitch amplitude: Determine the typical values ​​of the bionic flapping wing under different operating conditions. The typical values ​​are divided into small amplitude, medium amplitude and large amplitude to match different operating conditions. S32. Phase difference adjustment: By adjusting the effective angle of attack. With heave-induced angle of attack Matching relationship and the optimal phase difference value depends on the pitch amplitude, effective angle of attack and heave-induced angle of attack It can be calculated using the following formula: (3) (4) (5) In the formula, Free flow velocity at the entrance. Vertical flow velocity; S4. Set the pitch frequency to be equal to the heave frequency; S5. Adjust the pitch motion mode according to the pitch amplitude: When the pitch amplitude is small, use harmonic pitch motion; when the pitch amplitude is large, use non-harmonic pitch motion. The equation for non-harmonic pitch motion is: (6) In the formula, β is a non-harmonic parameter, with a value range of 1.0-3.0; S6. Calculate the propulsion power coefficient and propulsion efficiency of the bionic flapping wing to verify the optimal value of the propulsion performance optimization of the bionic flapping wing: S61, Propulsion Power Coefficient The definition of is: (7) In the formula, ρ, , and These represent fluid density, horizontal hydrodynamic force, incoming flow velocity, airfoil chord length, and aspect ratio of the biomimetic flapping wing, respectively. S62, Propulsion Efficiency The definition of propulsion power coefficient With input power coefficient The ratio is calculated using the following formula: (8).

[0006] Furthermore, in step S1, the biomimetic flapping wing selects the NACA0012 airfoil, and the distance between the pitch axis and the leading edge of the flapping wing is 1 / 3 of the airfoil chord length.

[0007] Furthermore, in step S31, the bionic flapping wing is divided into three operating conditions: upstream propulsion, unpowered downstream propulsion, and high-efficiency downstream propulsion. The Reynolds number of the bionic flapping wing is 1100, and the pitch amplitude is divided into three typical values ​​using the immersion boundary method: a small amplitude of 30° for the upstream propulsion condition, a medium amplitude of 50° for the unpowered downstream propulsion condition, and a large amplitude of 76.3° for the high-efficiency downstream propulsion condition.

[0008] Furthermore, in step S32, the phase difference depends on the pitch amplitude. When the pitch amplitude is 30°, the phase difference is 270°; when the pitch amplitude is 50°, the phase difference is 180°; and when the pitch amplitude is 76.3°, the phase difference is 292.5°.

[0009] Furthermore, in step S4, the pitch frequency and the heave frequency are equal and both have a value of 0.16.

[0010] Furthermore, in step S5, when the pitch amplitude is 30° and 50°, harmonic pitch motion is used; when the pitch amplitude is 76.3°, non-harmonic pitch motion is used, and the non-harmonic parameter β is set to 2.25.

[0011] The beneficial effects of this invention are as follows: (1) By optimizing the phase difference under different working conditions, precise control of different propulsion directions is achieved. The upstream propulsion force is increased by more than 30% under small pitch amplitude, and efficient downstream propulsion can be achieved without external power under medium pitch amplitude. (2) Determine the optimal frequency matching relationship (frequency difference is 0), avoid the propulsion performance degradation caused by frequency mismatch, and ensure the stable and efficient operation of flapping wings under all working conditions; (3) Optimize the non-harmonic motion parameters for large pitch amplitude to improve propulsion efficiency to 24.10%, which is 71% higher than that of harmonic motion and significantly reduces energy loss; (3) The method is highly adaptable and the parameters can be flexibly adjusted according to different engineering needs (such as upstream propulsion, downstream propulsion, and non-powered propulsion), providing a standardized control scheme for the engineering application of flapping wing propulsion devices. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 is a schematic diagram of the structure and motion of the flapping wing in an embodiment of the present invention; Figure 2 shows the variation curves of propulsion power coefficient under different phase differences in the embodiments of the present invention; Figure 3 : This is a curve showing the effect of frequency difference on propulsion efficiency under different conditions in an embodiment of the present invention. Figure 4 is a comparison of propulsion power coefficients corresponding to different non-harmonic parameters in the embodiments of the present invention.

[0014] In the diagram: 1-flapping wing body; 2-torsion spring; 3-energy harvesting device; 4-pitch axis; 5-leading edge; 6-flow field direction. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions disclosed in this invention includes the following steps: S1. Select the NACA0012 airfoil as the bionic flapping wing airfoil. Connect the bionic flapping wing to the energy harvesting device through a torsion spring. The distance between the pitch axis and the leading edge of the flapping wing is 1 / 3 of the airfoil chord length, so that the bionic flapping wing can achieve coordinated heave and pitch movements.

[0017] S2, Set the movement mode of the bionic flapping wing: Since the biomimetic flapping wing simultaneously performs heave and pitch motions, and its heave motion is driven by waves while its pitch motion is driven by external power, the equation of motion for the biomimetic flapping wing is as follows: (1) (2) In the formula, For the heave and pitch displacement of biomimetic flapping wings, For the heave amplitude, For heave frequency, The pitch angle, For pitch amplitude, For pitch frequency, Phase difference; S3. Adjust the phase difference and pitch amplitude to match the motion patterns of the bionic flapping wing under different operating conditions to improve the propulsion efficiency of the bionic flapping wing: S31. Adjustment of Pitch Amplitude: Pitch amplitude affects propulsion performance boundaries (direction, power requirements). Phase difference achieves performance extrema within these boundaries, exhibiting a "fixed amplitude range, fixed phase extrema" characteristic. All optimal phase differences are based on the premise that "frequency difference = 0" (i.e., pitch frequency equals heave frequency). This premise has been verified by simulation as a universally optimal match across the entire amplitude range. Under this premise, there are methods for adjusting pitch amplitude and phase difference, as follows: Based on engineering requirements (upstream propulsion, unpowered downstream propulsion, and high-efficiency downstream propulsion), and combined with numerical simulation using the immersion boundary method (IBM, Reynolds number 1100), pitch amplitude is divided into three typical values: small amplitude 30° (suitable for upstream propulsion), medium amplitude 50° (suitable for unpowered downstream propulsion), and large amplitude 76.3° (suitable for high-efficiency downstream propulsion). These three amplitude values ​​are key inflection points for propulsion performance, covering mainstream application scenarios. S32. Phase difference adjustment: The effective angle of attack and the heave-induced angle of attack are matched by adjusting the phase difference. The optimal phase difference value depends on the pitch amplitude. When the pitch amplitude is 30°, the phase difference is 270°; when the pitch amplitude is 50°, the phase difference is 180°; when the pitch amplitude is 76.3°, the phase difference is 292.5°.

[0018] S4. Set the pitch frequency to be equal to the heave frequency, with a value of 0.16.

[0019] S5. Adjusting the pitch motion mode based on the pitch amplitude: When the pitch amplitude is 30° and 50°, harmonic pitch motion is used; when the pitch amplitude is 76.3°, non-harmonic pitch motion is used. The non-harmonic parameter β is set to 2.25, and the dwell time of the flapping wing at the maximum pitch angle is extended. The equation for the non-harmonic pitch motion is: (6) In the formula, β is a non-harmonic parameter, with a value range of 1.0-3.0; S6. Calculate the propulsion power coefficient and propulsion efficiency of the bionic flapping wing to verify the optimal value of the propulsion performance optimization of the bionic flapping wing: S61, Propulsion Power Coefficient The definition of is: (7) In the formula, ρ, , and These represent fluid density, horizontal hydrodynamic force, incoming flow velocity, airfoil chord length, and aspect ratio of the biomimetic flapping wing, respectively. S62, Propulsion Efficiency The definition of propulsion power coefficient With input power coefficient The ratio is calculated using the following formula: (8).

[0020] Furthermore, in step S5, when the pitch amplitude is 30°, harmonic pitch motion is used; when the pitch amplitude is 76.3°, non-harmonic pitch motion is used, and the non-harmonic parameter β is set to 2.25.

[0021] As shown in Figure 1, the biomimetic flapping wing of the present invention adopts the flapping wing body 1 of the NACA0012 airfoil, which is connected to the energy harvesting device 3 through the torsion spring 2. The distance between the pitch axis 4 and the leading edge 5 of the biomimetic flapping wing is set to 1 / 3 of the airfoil chord length c, so as to ensure the flexibility of movement and the stability of structure.

[0022] Select the corresponding operating parameters based on the target advancement requirements. The specific implementation method is as follows: Example 1: Upstream propulsion (small pitch amplitude condition) Set the pitch amplitude of the flapping wing heave amplitude (c is the chord length) The frequencies of both heave and pitch motions are set to be... (Reduced frequency), frequency difference is 0; Set phase difference Harmonic pitch motion mode (β=1.0) is adopted. The Reynolds number of the flow field was controlled at 1100. Numerical simulation was performed using the immersed boundary method. At this time, the effective angle of attack of the flapping wing was less than the heave-induced angle of attack, the upstream propulsion power coefficient reached 0.3, and the propulsion efficiency was improved by 25% compared with conventional parameters.

[0023] Example 2: Unpowered downstream propulsion (medium pitch amplitude condition) Set the pitch amplitude of the flapping wing heave amplitude The frequencies of both heave and pitch motions are set to be... The frequency difference is 0; Set phase difference It adopts a harmonic pitch motion mode; Without requiring external power, the flapping wing relies on hydrodynamics for downstream propulsion, achieving a maximum propulsion power coefficient of 1.8815 and a propulsion efficiency of 58.50%.

[0024] Example 3: High-efficiency downstream propulsion (large pitch amplitude condition) Set the pitch amplitude of the flapping wing heave amplitude ; The frequencies of both heave and pitch motions are set to be... The frequency difference is 0; Set phase difference The non-harmonic pitch motion mode is adopted, with non-harmonic parameter β=2.25; The flapping wing has a longer dwell time at the maximum pitch angle, and its propulsion efficiency reaches 24.10%, which is 71% higher than that of harmonic motion with β=1.0, and its propulsion power coefficient reaches 2.66.

[0025] This invention significantly improves propulsion performance by systematically controlling the motion parameters of flapping wings, providing a scientific basis and engineering guidance for the design and optimization of biomimetic flapping wing propulsion devices.

[0026] In the description of this specification, references to terms such as "an embodiment," "example," and "specific example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions, characterized in that, Includes the following steps: S1. Select the airfoil of the bionic flapping wing, connect the bionic flapping wing to the energy harvesting device through a torsion spring, and set the pitch axis and leading edge distance of the bionic flapping wing so that the bionic flapping wing can achieve coordinated heave and pitch movements. S2, Set the movement mode of the bionic flapping wing: Since the biomimetic flapping wing simultaneously performs heave and pitch motions, and its heave motion is driven by waves while its pitch motion is driven by external power, the equation of motion for the biomimetic flapping wing is as follows: （1） （2） In the formula, For the heave and pitch displacement of biomimetic flapping wings, For the heave amplitude, For heave frequency, The pitch angle, For pitch amplitude, For pitch frequency, Phase difference; S3. Adjust the phase difference and pitch amplitude to match the motion patterns of the bionic flapping wing under different operating conditions to improve the propulsion efficiency of the bionic flapping wing: S31. Adjustment of pitch amplitude: Determine the typical values ​​of the bionic flapping wing under different operating conditions. The typical values ​​are divided into small amplitude, medium amplitude and large amplitude to match different operating conditions. S32. Phase difference adjustment: By adjusting the effective angle of attack. With heave-induced angle of attack Matching relationship and the optimal phase difference value depends on the pitch amplitude, effective angle of attack and heave-induced angle of attack It can be calculated using the following formula: （3） （4） （5） In the formula, Free flow velocity at the entrance. Vertical flow velocity; S4. Set the pitch frequency to be equal to the heave frequency; S5. Adjust the pitch motion mode according to the pitch amplitude: When the pitch amplitude is small, use harmonic pitch motion; when the pitch amplitude is large, use non-harmonic pitch motion. The equation for non-harmonic pitch motion is: （6） In the formula, β is a non-harmonic parameter, with a value range of 1.0-3.0; S6. Calculate the propulsion power coefficient and propulsion efficiency of the bionic flapping wing to verify the optimal value of the propulsion performance optimization of the bionic flapping wing: S61, Propulsion Power Coefficient The definition of is: （7） In the formula, ρ, , and These represent fluid density, horizontal hydrodynamic force, incoming flow velocity, airfoil chord length, and aspect ratio of the biomimetic flapping wing, respectively. S62, Propulsion Efficiency The definition of propulsion power coefficient With input power coefficient The ratio is calculated using the following formula: （8）。 2. The method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions according to claim 1, characterized in that, In step S1, the biomimetic flapping wing selects the NACA0012 airfoil, and the distance between the pitch axis and the leading edge of the flapping wing is 1 / 3 of the airfoil chord length.

3. The method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions according to claim 2, characterized in that, In step S31, the bionic flapping wing is divided into three operating conditions: upstream propulsion, unpowered downstream propulsion, and high-efficiency downstream propulsion. The Reynolds number of the bionic flapping wing is 1100, and the pitch amplitude is divided into three typical values ​​using the immersion boundary method: a small amplitude of 30° for the upstream propulsion condition, a medium amplitude of 50° for the unpowered downstream propulsion condition, and a large amplitude of 76.3° for the high-efficiency downstream propulsion condition.

4. The method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions according to claim 3, characterized in that, In step S32, the phase difference depends on the pitch amplitude. When the pitch amplitude is 30°, the phase difference is 270°; when the pitch amplitude is 50°, the phase difference is 180°; and when the pitch amplitude is 76.3°, the phase difference is 292.5°.

5. The method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions according to claim 4, characterized in that, In step S4, the pitch frequency and the heave frequency are equal and both have a value of 0.

16.

6. The method for optimizing the propulsion performance of a biomimetic flapping wing under multiple operating conditions according to claim 5, characterized in that, In step S5, when the pitch amplitude is 30° and 50°, harmonic pitch motion is used; when the pitch amplitude is 76.3°, non-harmonic pitch motion is used, and the non-harmonic parameter β is set to 2.25.

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