A method for acquiring pneumatic parameters

Abstract

The application provides a kind of aerodynamic parameter acquisition method, comprising the following steps: grid division is carried out to the flow field of the measured object, and the result is output;According to the state parameters of the measured object, the physical parameters of the measured object, the pressure far field name, the viscosity model, the grid and the aerodynamic data processing parameters, the script file for acquiring and processing aerodynamic parameters is written;According to the script file and the divided grid, the aerodynamic parameters of the measured object are processed to obtain the processed aerodynamic parameters.The application improves the stability of calculation, reduces the calculation divergence caused by improper human setting, saves the trial and error cost, and improves the accuracy of unmanned aerial vehicle aerodynamic parameter acquisition.

Description

Technical Field

[0001] This invention belongs to the field of CFD calculation technology, specifically relating to a method for obtaining aerodynamic parameters. Background Technology

[0002] Acquiring aerodynamic parameters for UAVs often relies on Fluent decomposition. Steady-state CFD calculations are not only fundamental for acquiring conventional aerodynamic data but also crucial inputs for unsteady calculations. Current techniques frequently employ fixed parameters such as relaxation factors, CFL numbers, and iteration steps, failing to adequately leverage the characteristics of CFD methods to enhance computational stability and accelerate computation. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for obtaining aerodynamic parameters. The solution of this invention can solve the problems existing in the prior art.

[0004] The technical solution of this invention:

[0005] A method for obtaining aerodynamic parameters includes the following steps:

[0006] The flow field domain of the measured object is meshed, and the results are output.

[0007] Based on the state parameters of the object under test, the physical parameters of the object under test, the name of the pressure far field, the viscosity model, the mesh and the aerodynamic data processing parameters, write a script file for acquiring and processing aerodynamic parameters;

[0008] Based on the script file and the divided grid, the aerodynamic parameters of the object under test are processed to obtain the processed aerodynamic parameters.

[0009] Furthermore, the state parameters of the object under test include flight Mach number, angle of attack range, sideslip angle range, and flight altitude; the physical parameters of the object under test include the torque reference point, reference area, and reference length; and the aerodynamic data processing parameters include the minimum CFL number C. min Maximum number of CFLs C max Minimum relaxation factor ω min Maximum relaxation factor ω max The relaxation factor and CFL number change steps nstep, the CFL number increase factor f1, the relaxation factor decrease factor f2, the grid scaling factor, and the minimum number of iterations nrun to ensure convergence.

[0010] Furthermore, the method for generating the script file includes the following steps:

[0011] S2.1 Write a function to read a portion of the mesh based on the input mesh name;

[0012] S2.2 Write the part that scales the mesh based on the input mesh scaling factor;

[0013] S2.3 Write the section that sets the viscosity model to be used for calculation based on the input viscosity model;

[0014] S2.4 This section describes how to set the torque reference point, reference area, and reference length to be used in the calculation based on the input torque reference point, reference area, and reference length.

[0015] S2.5 is a section that sets the pressure far-field boundary conditions used in the calculation based on the input Mach number, flight altitude, angle of attack sideslip range, and pressure far-field name.

[0016] S2.6 Write an nstep function based on the input, C min C max ω min ω max For f1 and f2, every nstep steps, the number of CFLs and the relaxation factor are dynamically adjusted until the number of CFLs reaches C. max The relaxation factor reaches ω min Part of;

[0017] S2.7 Based on second-order precision, the relaxation factor is taken as the minimum value ω of the input. min CFL numbers take the maximum value C of the input. max The number of iterations to obtain aerodynamic data, nrun 实际， Obtain aerodynamic data.

[0018] Furthermore, adjust the CFL number to reach C max The relaxation factor reaches ω min The method includes the following steps:

[0019] When S2.6.1i=1, calculate the values ​​of the relaxation factor ω and the CFL number using the following formula:

[0020] C = C min *exp(1+i*f1), ω=ω max *exp(1-i*f2),

[0021] Where, f1 = 1 / exp(k), f2 = 1 / exp(k) 2 ), k=(∑C a ) / 40000, ∑C a This represents the cumulative sum of the number of CFLs used in each step of the iteration up to the current step a;

[0022] S2.6.2 loop S2.6.1 nstep times to obtain C1 and ω1;

[0023] S2.6.3 Increment the value of i by 1. Substitute C1 and ω1 into C and ω in S2.6.1, and then loop S2.6.1 for nstep times to obtain C2 and ω2. And when C2 >= C max , then take C2 = C max ; ω2 <= ω min , then take ω2 = ω min ;

[0024] S2.6.4 Loop S2.6.3 until i < n, where n = [nrun / nstep], to obtain Cn = C max , ωn = ω min .

[0025] Furthermore, the nrun[[ID=1​​​​​​​​​​​​​​​​​​​​​​​​​​​It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. 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 a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] like Figure 1 As shown, according to an embodiment of the present invention, a method for obtaining aerodynamic parameters is provided, comprising the following steps:

[0035] Step 1: Grid the flow field domain of the object under test and output the results;

[0036] Step 2: Based on the state parameters of the object under test, the physical parameters of the object under test, the name of the pressure far field, the viscosity model, the mesh, and the aerodynamic data processing parameters, write a script file for acquiring and processing aerodynamic parameters.

[0037] In a further embodiment, the state parameters of the object under test include flight Mach number, angle of attack range, sideslip angle range, and flight altitude; the physical parameters of the object under test include the torque reference point, reference area, and reference length; and the aerodynamic data processing parameters include minimum and maximum CFL numbers (C...). min C max ), minimum and maximum relaxation factors (ω) min ω max The relaxation factor and CFL number change steps (nstep), CFL number increase factor (f1), relaxation factor decrease factor (f2), grid scaling factor, and minimum number of iterations to ensure convergence (nrun).

[0038] In a further embodiment, the method for generating the script file includes the following steps:

[0039] S2.1 Write a function to read a portion of the mesh based on the input mesh name;

[0040] S2.2 Write the part that scales the mesh based on the input mesh scaling factor;

[0041] S2.3 The section for setting the viscosity model to be used for calculation based on the input viscosity model; preferably, the viscosity model can be selected from inviscid, laminar or SA models.

[0042] S2.4 This section describes how to set the torque reference point, reference area, and reference length to be used in the calculation based on the input torque reference point, reference area, and reference length.

[0043] S2.5 is a section that sets the pressure far-field boundary conditions used in the calculation based on the input Mach number, flight altitude, angle of attack sideslip range, and pressure far-field name.

[0044] S2.6 Write an nstep function based on the input, C min C max ω min ω max For f1 and f2, every nstep steps, the number of CFLs and the relaxation factor are dynamically adjusted until the number of CFLs reaches C. max The relaxation factor reaches ω min Part of;

[0045] In another embodiment, the CFL number is adjusted to reach C max The relaxation factor reaches ω min The method includes the following steps:

[0046] When S2.6.1i=1, calculate the values ​​of the relaxation factor ω and the CFL number using the following formula:

[0047] C = C min *exp(1 + i*f1), ω = ω max *exp(1 - i*f2),

[0048] where f1 = 1 / exp(k), f2 = 1 / exp(k 2 ), k = (∑C a ) / 40000, ∑C a represents the cumulative sum value of the CFL numbers used in each step after iterating to the current a-th step;

[0049] S2.6.2 Loop S2.6.1 nstep times to obtain C1 and ω1;

[0050] S2.6.3 Increment the value of i by 1, substitute C1 and ω1 into C and ω in S2.6.1, and then loop S2.6.1 nstep times to obtain C2 and ω2. And when C2 >= C max , then take C2 = C max ; ω2 <= ω min , then take ω2 = ω min ;

[0051] S2.6.4 Loop S2.6.3 until i < n, where n = [nrun / nstep], to obtain Cn = C max , ωn = ω min .

[0052] S2.7 Write a script to obtain the aerodynamic data according to the second-order accuracy, with the relaxation factor taking the minimum value ω min , and the CFL number taking the maximum value C max input, and obtain the number of iterations nrun for the aerodynamic data 实际， to obtain the aerodynamic data.

[0053] Further, in one embodiment, nrun 实际 = min(nrun, [|40000 - ∑C a | / C max + 1), where min(,) represents taking the minimum value within (), and || represents taking the absolute value within ||.

[0054] Step 3: Process the aerodynamic parameters of the object under test according to the script file and the divided grid to obtain the processed aerodynamic parameters.

[0055] To have a further understanding of an aerodynamic parameter acquisition method provided by the present invention, the following will be described in detail with specific examples.

[0056] Taking the acquisition of aerodynamic data in Fluent using Matlab as an example, an aerodynamic parameter acquisition method includes the following steps:

[0057] Step 1: Mesh the flow field domain of the object under test and output the results as a Fluent-specific *.cas file;

[0058] Step 2: Based on the state parameters of the object under test, the physical parameters of the object under test, the pressure far-field name, the viscosity model, the mesh and aerodynamic data processing parameters, convert them into parameters that Fluent can recognize and write a Fluent TUI script file with the suffix jou.

[0059] Step 3: Place the *.jou and *.cas files in the same directory, run Fluent, and directly read *.jou. Fluent will execute the statements in *.jou. After execution, you will get the drone force and torque files *-force.dat and *-moment.dat.

[0060] Table 1 shows a comparison of the performance of this method with conventional calculations for a specific UAV.

[0061]

[0062] As can be seen from the table, the aerodynamic parameter acquisition method of the present invention can obtain smaller residuals and more accurate values ​​with the same number of iterations.

[0063] In summary, the aerodynamic parameter acquisition method provided by this invention has at least the following advantages compared to existing technologies:

[0064] (1) This invention improves the stability of calculation by dynamically adjusting the relaxation factor and CFL number, reduces the calculation divergence caused by improper human settings, saves trial and error costs, and improves the accuracy of obtaining UAV aerodynamic parameters.

[0065] (2) By setting up scripts, this invention reduces the downtime and error probability caused by manually modifying calculation parameters, and improves the accuracy and efficiency of obtaining UAV aerodynamic parameters.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for obtaining aerodynamic parameters, characterized in that, Includes the following steps: The flow field domain of the measured object is meshed, and the results are output. Based on the state parameters of the object under test, the physical parameters of the object under test, the name of the pressure far field, the viscosity model, the grid, and the aerodynamic data processing parameters, write a script file to acquire and process the aerodynamic parameters; the state parameters of the object under test include the flight Mach number, angle of attack range, sideslip angle range, and flight altitude; the physical parameters of the object under test include the torque reference point, reference area, and reference length of the object under test. The aerodynamic data processing parameters include minimum CFL number C min , maximum CFL number C max , minimum relaxation factor ω min , maximum relaxation factor ω max , relaxation factor and CFL number change step number nstep, CFL number increasing coefficient f1, relaxation factor decreasing coefficient f2, grid scaling factor, and minimum iteration step number nrun for ensuring convergence. Based on the script file and the divided grid, the aerodynamic parameters of the object under test are processed to obtain the processed aerodynamic parameters. Adjusting CFL number to reach C max , relaxation factor to reach ω min The method comprises the following steps: S2.6.1, when i=1, calculate the values ​​of the relaxation factor ω and the number of CFLs, using the following formula: C = C min * exp(1 + i * f1), ω = ω max * exp(1 - i * f2), where f1 = 1 / exp(k), f2 = 1 / exp(k) 2 ), k = (∑C a ) / 40000, ∑C a denotes the cumulative sum of CFLs used up to the current a step. S2.6.2, loop S2.6.1 nstep times to obtain C1 and ω1; S2.6.3, i value is incremented by 1, C1 and ω1 are brought into C and ω in S2.6.1, then S2.6.1 is looped nstep times to obtain C2 and ω2, and when C2 >= C max , take C2 = C max ; ω2 <= ω min , take ω2 = ω min ; S2.6.4, loop S2.6.3, until i < n, where n = [nrun / nstep], obtain Cn= C max , ωn= ω min .

2. The method for obtaining aerodynamic parameters according to claim 1, characterized in that, The method for generating the script file includes the following steps: S2.1, Write the part that reads the mesh based on the input mesh name; S2.2, Write the part that scales the mesh based on the input mesh scaling factor; S2.3, Write the part that sets the viscosity model to be used for calculation based on the input viscosity model; S2.4, Write the part that sets the torque reference point, reference area, and reference length to be used in the calculation based on the input torque reference point, reference area, and reference length; S2.5, This section describes how to set the pressure far-field boundary conditions used in the calculation based on the input Mach number, flight altitude, angle of attack and sideslip angle range, and pressure far-field name. S2.6, Write an nstep function based on the input, C min C max ω min ω max For f1 and f2, every nstep steps, the number of CFLs and the relaxation factor are dynamically adjusted until the number of CFLs reaches C. max The relaxation factor reaches ω min Part of; S2.7, Write code that, based on second-order precision, takes the minimum value ω of the input as the relaxation factor. min CFL numbers take the maximum value C of the input. max The number of iterations to obtain aerodynamic data, nrun 实际， Obtain aerodynamic data.

3. The method for obtaining aerodynamic parameters according to claim 2, characterized in that, The actual value of nrun is min(nrun, [|40000-∑C a | / C max ]+1), where min(,) means taking the minimum value within (), and || means taking the absolute value within ||.

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