A method for analyzing aerodynamic characteristics of a single-layer gliding parachute based on optical topography measurement

Abstract

The application discloses a single-layer gliding parachute aerodynamic characteristic analysis method based on optical shape measurement, and high-precision measurement of key factors in single-layer gliding parachute aerodynamic characteristic analysis is realized by using existing technologies, so that the most critical obstacle in aerodynamic characteristic analysis of flexible structure parachutes by using the relatively mature CFD method is overcome.

Description

Technical Field

[0001] This invention belongs to the field of parachute aerodynamic characteristic analysis technology, and particularly relates to a method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement. Background Technology

[0002] A paraglider is a parachute that can generate a force perpendicular to the direction of the airflow. In order to have a better guiding effect on the airflow, it is usually made of a material with low air permeability. During steady gliding, the air permeability is negligible.

[0003] Analyzing the aerodynamic characteristics of parachutes is a necessary step in optimizing their design using scientific methods. Currently, this mainly involves two types of techniques: simulation and experimentation.

[0004] Existing parachute testing techniques primarily involve mechanical measurements of the parachute system. This method suffers from problems such as large fluctuations in measurement results, inability to comprehensively obtain structural stress and flow field distribution, and difficulty in conducting in-depth analysis.

[0005] Optical measurement methods can also be used in parachute testing. Currently, optical measurement is mainly used to measure the overall motion trajectory of the system. High-precision optical measurement of the internal state of the system is rarely used in the parachute field, and it has not yet been applied to single-layer paragliders.

[0006] Existing parachute simulation analysis techniques suffer from high computational difficulty and low accuracy, and are mainly divided into two categories: Computational Fluid Dynamics (CFD) and Fluid-Structure Interaction (FSI). Among them, the simulation using the FSI method is affected by the accumulation of errors, and the calculation results are prone to divergence and are difficult to converge to an equilibrium state. Even if stable calculation results can be output, they often differ greatly from mechanical measurement data, and this method has high computational requirements.

[0007] Computational fluid dynamics methods are relatively mature (efficient and accurate), but they can only analyze rigid bodies without air permeability. Parachutes are flexible and permeable structures. When using this method for simulation, it is necessary to input the fully inflated aerodynamic shape of the parachute and make rigid body assumptions. However, there is currently a lack of theoretical support for obtaining the accurate fully inflated aerodynamic shape of the parachute.

[0008] Currently, aerodynamic characteristic analysis and optimization of parachutes, especially paragliders, usually requires a large number of experiments to obtain sufficient mechanical measurement samples, resulting in huge investments in materials and human resources. Simulation analysis methods can only provide qualitative reference conclusions at present, and quantitative analysis cannot be achieved. Summary of the Invention

[0009] Purpose of the invention

[0010] To overcome the problems of high cost and difficulty in in-depth analysis of existing experimental methods, and the high computational difficulty and low accuracy of simulation technology, this invention provides an analysis method that uses optical measurement to obtain aerodynamic shape as simulation input, in order to better integrate and complement various existing technologies and help designers analyze and optimize the aerodynamic characteristics of single-layer paragliders.

[0011] Invention Technology Solutions

[0012] A method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement includes the following steps:

[0013] (1) Make a test piece of the single-layer paraglider of the research object, with optically identifiable feature points distributed on its canopy;

[0014] (2) Establish a geometric model based on the size and material properties of the test piece in step (1) at a 1:1 ratio, and set a load suspension point at a distance H from the geometric center of the umbrella canopy below the umbrella canopy;

[0015] (3) Fix the load suspension point on the force balance at a distance H from the center of the wind tunnel, pre-place the canopy at the center of the wind tunnel, increase the wind tunnel flow velocity from 0, and remove the excess constraints on the test piece after the canopy is fully expanded and stable in the flow field, leaving only the constraints at the load suspension point.

[0016] (4) Record the image of the test piece in a stable, fully expanded shape in the flow field, interpret all the feature points on one side of the canopy, perform data processing to obtain the coordinates of each feature point, and fit the feature points on each edge into a function curve;

[0017] (5) Discretize the geometric model established in step (2) to obtain a finite element model and obtain the geometric model after the umbrella canopy is fully opened;

[0018] (6) Export the discrete coordinate point cloud of the umbrella canopy obtained by simulation in step (5), and compare it with the feature point coordinates obtained in step (4) to ensure that the overall error does not exceed the set value.

[0019] (7) Based on the coordinates of each key point obtained in step (4), the point cloud model exported in step (6) is corrected and fitted to obtain a complete analytical model of the umbrella canopy's fully opened surface.

[0020] (8) The full-expansion curved surface of the paraglider obtained in step (7) is simulated using computational fluid dynamics (CFD) to obtain the steady-state aerodynamic characteristics of the single-layer paraglider in this state.

[0021] (9) Adjust the structure of the research object, repeat steps (1) to (8), analyze the variation law of steady-state full shape and steady-state aerodynamic characteristics of single-layer paraglider under different structures, refer to the data obtained by simulation calculation in step (5) for analysis, and optimize the structure of single-layer paraglider according to the design goal.

[0022] Preferably, in step (1), each key part of the umbrella canopy has a pattern with clear feature points as feature points that can be optically identified.

[0023] Preferably, in step (4), a multi-view stereo vision test method is used to record the image of the umbrella.

[0024] Preferably, in step (4), high-definition cameras are placed before and after the test piece that is stably tensioned.

[0025] Preferably, the simulation calculation in step (5) is performed using the same environmental parameters as the test in step (4).

[0026] Preferably, in step (5), the arbitrary Lagrange-Euler method is used for simulation calculation.

[0027] Preferably, the overall error in step (6) does not exceed 5%.

[0028] Preferably, the steady-state aerodynamic characteristics in step (8) include the lift, drag, and pressure distribution of the surrounding flow field generated by the single-layer paraglider.

[0029] Preferably, in step (9), the stress distribution on the umbrella structure obtained by step 5 is used to perform strength analysis, and the structure of the single-layer paraglider is optimized according to the design objectives.

[0030] The advantages of this invention are as follows: This analytical method utilizes existing technologies to perform high-precision measurements of key factors in the aerodynamic characteristic analysis of single-layer paragliders. It overcomes the most critical obstacle in using currently mature CFD methods for aerodynamic characteristic analysis of flexible structure paragliders. By integrating and complementing existing technologies, it expands the capabilities of existing simulation technologies in the aerodynamic characteristic analysis of single-layer paragliders, enabling them to be better used for auxiliary analysis, thereby significantly reducing experimental investment. It also provides more accurate and comprehensive data for in-depth analysis of the characteristic mechanisms of single-layer paragliders, helping designers to better understand and master single-layer paraglider design technology. The method has a clear workflow, strong operability, and significant practical value. Attached Figure Description

[0031] Figure 1 This is a flowchart of a method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement according to the present invention.

[0032] Figure 2 This is a plan view of the canopy of a single-layer paraglider, the subject of this invention.

[0033] Figure 3 This is a theoretical geometric model illustration of the single-layer paraglider, the subject of this invention.

[0034] Figure 4 This is a schematic diagram of wind tunnel optical measurement.

[0035] In the picture: 1-canopy, 2-parachute lines, 3-measuring balance, 4-camera B, 5-camera A. Detailed Implementation

[0036] The present invention is achieved through the following technical solution.

[0037] Reference Figures 1-4 A method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement includes the following steps:

[0038] (1) A test piece of the single-layer paraglider of the research object is made, the canopy of which is distributed with optically identifiable feature points; in this embodiment, the planar shape of the canopy is as follows: Figure 2 As shown, point O is the geometric center of the canopy plane, and the canopy material has a uniformly distributed grid pattern with clear intersections.

[0039] (2) Based on the dimensions and material properties of the sample made in step (1), establish a geometric model at a 1:1 scale, such as... Figure 3 As shown, let H be the distance from the load suspension point P to the geometric center P of the umbrella canopy;

[0040] (3) Fix the load suspension point on a force balance at a distance H from the center of the wind tunnel. Pre-position the canopy at the center of the wind tunnel. Increase the wind tunnel velocity from 0. After the canopy is fully expanded and stable in the flow field, remove the redundant constraints on the test piece, leaving only the constraints at the load suspension point P. Figure 4 As shown;

[0041] (4) Using a binocular stereo vision testing method, high-definition cameras were placed in front of and behind a stably fully opened single-layer paraglider. The specific camera positions are as follows: Figure 4 Cameras A5 and B4 record images of the test piece in a stable, fully expanded shape in the flow field from a dual-view perspective. They also interpret all key points on each edge of the umbrella canopy, process the data to obtain the coordinates of each point, and fit them into a continuous curve.

[0042] (5) Discretize the geometric model established in step (2) to obtain the finite element model, set the same environmental parameters as in step (4) test, and use the arbitrary Lagrange-Euler method (ALE, a fluid-structure interaction calculation method) for simulation calculation;

[0043] (6) Export the discrete coordinate point cloud of the umbrella canopy obtained by simulation in step (5) and compare it with the edge curves obtained in step (4). The overall error shall not exceed 5%.

[0044] (7) Using the edge curves obtained in step (4) as the generatrix, the edge curves of the point cloud model exported in step (6) are corrected and fitted, and the model is swept into the inside of the canopy to obtain the complete canopy full shape.

[0045] (8) Perform fluid dynamics simulation calculations on the full-expansion curved surface of the paraglider obtained in step (7) to obtain the steady-state aerodynamic characteristics of the single-layer paraglider under this state, including the lift, drag, and pressure distribution of the surrounding flow field.

[0046] (9) Adjust the structure of the research object, repeat steps (1) to (8), analyze the variation law of steady-state full shape and steady-state aerodynamic characteristics of single-layer paraglider under different structures, refer to the stress distribution on the paraglider structure obtained by step (5) for strength analysis, and optimize the structure of single-layer paraglider according to the design goal.

[0047] The scope of protection of this invention is not limited to the embodiments described above. Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its scope. If such modifications and variations fall within the scope of the claims of this invention and their equivalents, then the intent of this invention also includes these modifications and variations.

Claims

1. A method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement, characterized in that, Includes the following steps: (1) Make a test piece of the single-layer paraglider of the research object, with optically identifiable feature points distributed on its canopy; (2) Establish a geometric model based on the size and material properties of the test piece in step (1) at a 1:1 ratio, and set a load suspension point at a position H below the umbrella canopy and at a distance H from the geometric center of the umbrella canopy; (3) Fix the load suspension point on the force balance at a distance H from the center of the wind tunnel, pre-place the canopy at the center of the wind tunnel, increase the wind tunnel flow velocity from 0, and remove the excess constraints on the test piece after the canopy is fully expanded and stable in the flow field, leaving only the constraints at the load suspension point. (4) Record the image of the test piece in a stable, fully expanded shape in the flow field, interpret all the feature points on one side of the canopy, perform data processing to obtain the coordinates of each feature point, and fit the feature points on each edge into a function curve; (5) Discretize the geometric model established in step (2) to obtain a finite element model and obtain the geometric model after the umbrella canopy is fully opened; (6) Export the discrete coordinate point cloud of the umbrella canopy obtained by simulation in step (5), and compare it with the feature point coordinates obtained in step (4) to ensure that the overall error does not exceed the set value. (7) Based on the coordinates of each key point obtained in step (4), the point cloud model exported in step (6) is corrected and fitted to obtain a complete analytical model of the umbrella canopy's fully opened surface. (8) The full-expansion surface of the parachute obtained in step (7) is simulated using computational fluid dynamics to obtain the steady-state aerodynamic characteristics of a single-layer paraglider in the full-expansion state. (9) Adjust the structure of the research object, repeat steps (1) to (8), analyze the variation law of steady-state full shape and steady-state aerodynamic characteristics of single-layer paraglider under different structures, refer to the data obtained by simulation calculation in step (5) for analysis, and optimize the structure of single-layer paraglider according to the design goal.

2. The method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement as described in claim 1, characterized in that, In step (1), each key part of the umbrella canopy has a pattern with clear feature points as feature points that can be optically identified.

3. The method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement as described in claim 1, characterized in that, In step (4), the image of the umbrella is recorded using a multi-view stereo vision test method.

4. The method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement as described in claim 3, characterized in that, In step (4), high-definition cameras are placed before and after the test piece that is stably tensioned.

5. The method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement as described in claim 3, characterized in that, In step (5), the same environmental parameters are set for the simulation calculation as in step (4) for the test.

6. The method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement as described in claim 3, characterized in that, In step (5), the arbitrary Lagrange-Euler method is used for simulation calculation.

7. The method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement as described in claim 1, characterized in that, The overall error in step (6) shall not exceed 5%.

8. The method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement as described in claim 1, characterized in that, In step (8), the steady-state aerodynamic characteristics include the lift, drag, and pressure distribution of the surrounding flow field generated by the single-layer paraglider.

9. The method for analyzing the aerodynamic characteristics of a single-layer paraglider based on optical topography measurement as described in claim 1, characterized in that, In step (9), the stress distribution on the umbrella structure obtained by step 5 is used to perform strength analysis, and the structure of the single-layer paraglider is optimized according to the design objectives.

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