CN109800543B - Optimal harmonic frequency selection method for simulating atmospheric turbulence phase screen - Google Patents
Optimal harmonic frequency selection method for simulating atmospheric turbulence phase screen Download PDFInfo
- Publication number
- CN109800543B CN109800543B CN201910234014.2A CN201910234014A CN109800543B CN 109800543 B CN109800543 B CN 109800543B CN 201910234014 A CN201910234014 A CN 201910234014A CN 109800543 B CN109800543 B CN 109800543B
- Authority
- CN
- China
- Prior art keywords
- harmonic frequency
- optimal harmonic
- optimal
- power ratio
- phase screen
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
Abstract
The optimal harmonic frequency selection method for simulating the atmospheric turbulence phase screen is used for improving the accuracy of optimal harmonic frequency selection. The method comprises the following steps of firstly setting initial conditions, selecting a comprehensive power ratio, then calculating preliminary optimal harmonic frequency according to the initial conditions and the comprehensive power ratio, and finally carrying out approximate rounding on the preliminary optimal harmonic frequency according to actual conditions to obtain final optimal harmonic frequency. The invention utilizes the initial condition and the comprehensive power ratio to determine the optimal harmonic frequency, not only has short calculation time, but also can rapidly and accurately select the needed optimal harmonic frequency according to actual conditions. The method is suitable for the von K-rmn phase power spectral density model and the modified von K-rmn phase power spectral density model, and can provide convenience for the research of atmospheric turbulence effect.
Description
Technical Field
The invention relates to the technical field of atmospheric turbulence, in particular to a method for selecting optimal harmonic frequency used when an atmospheric turbulence phase screen is simulated by using a subharmonic method, and belongs to the technical field of measurement.
Background
The free space optical communication has the advantages of large bandwidth, no need of frequency permission, high transmission rate, easy installation and erection and the like, so that the free space optical communication is widely applied to the fields of wireless sensing, navigation and aerospace, urban local area networks and the like. However, since the atmospheric turbulence causes fluctuation of the light intensity and phase of the laser, resulting in serious degradation of free space optical communication performance and even interruption of the communication link, it is necessary to study the effect of the atmospheric turbulence.
At present, methods for researching and simulating atmospheric turbulence mainly comprise an experimental analysis method, a theoretical analysis method and a numerical simulation method, wherein the numerical simulation method is most widely applied because of simplicity and easiness in implementation. The core of the numerical simulation method for researching the atmospheric turbulence effect is to adopt a random phase screen to simulate the atmospheric turbulence effect, such as a spectrum inversion method based on fast Fourier transform (Fast Fourier Transform, FFT), a Zernike polynomial method based on an orthogonal polynomial, a fractal method based on random midpoint displacement, a generation method based on random data element expansion and a multi-scale method based on wavelet analysis. The spectrum inversion method has the advantages of high calculation speed and applicability to different forms of atmospheric turbulence spectrum models, so that the spectrum inversion method becomes one of the most commonly used phase screen simulation methods, in particular to a subharmonic method. The accuracy of generating the phase screen by using the subharmonic method is related to the harmonic frequency, and the generated phase screen is more and more accurate along with the increase of the harmonic frequency. However, when the harmonic frequency exceeds a certain value, the accuracy of the phase screen is not obviously improved, the simulation time is only increased when the harmonic frequency is continuously increased, and even the value is changed, so that the optimal value exists in the harmonic frequency. At present, little research is done on how to accurately determine the optimal harmonic frequency, and when the atmospheric turbulence phase screen is simulated early, how much harmonic is added is not a basis, such as when Kolmogorov phase screen is simulated, lane et al adds 5 harmonics and Sedmak adds 10 harmonics. Later, sedmak studied the relationship between harmonic order and phase screen size and atmospheric turbulence external dimensions, giving some non-quantitative practical evaluation criteria. Then, marcel carbide improves it, defines two quantitative evaluation criteria-comprehensive power ratio and structural function ratio, but the comprehensive power ratio is only applicable to von K-rmn which is a spectrum model, and the result obtained by using the structural function ratio is a rough value and is not accurate enough.
From the above study, it can be seen that the feasibility and effectiveness of the subharmonic simulation atmospheric turbulence phase screen are undoubted, but how to accurately select the optimal harmonic frequency still has problems when generating the phase screen, and the accuracy is slightly insufficient. Therefore, it is necessary to design a new evaluation standard for selecting the optimal harmonic frequency, and improve the accuracy of selecting the optimal harmonic frequency, so that an accurate atmospheric turbulence phase screen can be generated.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the optimal harmonic frequency selection method for simulating the atmospheric turbulence phase screen, so as to improve the accuracy of optimal harmonic frequency selection.
The problems of the invention are solved by the following technical proposal:
the method comprises the steps of firstly setting initial conditions, selecting a comprehensive power ratio, then calculating initial optimal harmonic frequency according to the initial conditions and the comprehensive power ratio, and finally carrying out approximate rounding on the initial optimal harmonic frequency according to actual conditions to obtain final optimal harmonic frequency.
The optimal harmonic frequency selection method for simulating the atmospheric turbulence phase screen comprises the following specific steps of:
a. setting initial conditions, selecting comprehensive power ratio alpha Φ ：
(1) The initial conditions include: dimension D of phase screen and outer dimension L of atmospheric turbulence 0 ；
(2) Selecting the integrated power ratio, alpha Φ The value range of (2) is [0,1 ]]；
b. Based on the set initial conditions and the selected integrated power ratio alpha Φ Calculating preliminary optimal harmonic frequency p in_optimal ：
c. According to the actual conditions, p in_optimal Performing approximate rounding to obtain the final optimal harmonic frequency p optimal ：
(1) When the requirement on the accuracy of the phase screen is not lower than the requirement on the running speed, the final optimal harmonic frequency is as follows:
(2) when the requirement on the accuracy of the phase screen is lower than the requirement on the running speed, the final optimal harmonic frequency is as follows:
the optimal harmonic frequency selection method for simulating the atmospheric turbulence phase screen is characterized in that the comprehensive power ratio is set to alpha Φ ＝0.99。
The invention utilizes the initial condition and the comprehensive power ratio to determine the optimal harmonic frequency, not only has short calculation time, but also can rapidly and accurately select the needed optimal harmonic frequency according to actual conditions. The method is suitable for the von K-rmn phase power spectral density model and the modified von K-rmn phase power spectral density model, and can provide convenience for the research of atmospheric turbulence effect.
Drawings
The invention is further described in detail below with reference to the drawings and examples.
FIG. 1 is a flow chart for selecting optimal harmonic orders using the method of the present invention;
FIG. 2 is a model of the power spectral density of two phases von K-rmn and modified von K-rmn;
FIG. 3 (a) is the variation of the phase structure function of the modified von K-rm model with the number of harmonics;
fig. 3 (b) is the variation of the relative error function of the modified von K rm model with the number of harmonics.
The symbols used in the text and in the figures are: phi φ (f) Is the phase power spectral density, f is the spatial frequency, D φ (r) is a phase structure function, r is the distance between two sampling points, p is the harmonic order, alpha phi is the integrated power ratio, D is the size of the phase screen, L 0 Is the external scale of atmospheric turbulence, p in_optimal Is the preliminary optimal harmonic frequency, p optimal Is the final optimal harmonic order.
Detailed Description
The invention provides a method for selecting optimal harmonic frequency, which is used when an atmospheric turbulence phase screen is simulated by utilizing a subharmonic method, has short calculation time, is suitable for two practical phase power spectral density models of von Krmn and modified von Krmn, and can accurately select the needed optimal harmonic frequency according to actual conditions.
The basic idea of the technical scheme of the invention is as follows:
(1) Selecting the integrated power ratio alpha Φ . (2) According to the integrated power ratio alpha Φ Obtaining the preliminary optimal harmonic frequency p in_optimal . (3) According to the actual conditions, p in_optimal Performing approximate rounding to obtain the final optimal harmonic frequency p optimal 。
The detailed description of the specific steps of the invention is as follows:
(1) The initial conditions include: dimension D of phase screen and outer dimension L of atmospheric turbulence 0 The method comprises the steps of carrying out a first treatment on the surface of the Wherein the outer dimension L of the atmospheric turbulence 0 : refers to the main parameters describing the optical turbulence characteristics and their application in analysis of the light propagation effects. In Kolmogorov turbulence statistics theory, the outer dimension refers to the largest dimension of the inertial region.
(2) Selecting the integrated power ratio, generally set to alpha Φ ＝0.99；
Obtaining the preliminary optimal harmonic frequency p in_optimal ；
(1) when extremely high accuracy is required for the phase screen, p is in_optimal Performing upward approximate rounding, i.e. final optimal harmonic order
(2) When the requirement on the accuracy of the phase screen is lower than the requirement on the running speed, the phase screen is controlled to be p in_optimal Performing downward approximate rounding, namely final optimal harmonic frequency
In order to better understand the technical solution of the present invention, the present invention is further described below with reference to a calculation example.
Calculation example:
1. fig. 2 is a graph of two practical phase power spectral density models, von K rmn and modified von K rmn, we take the modified von K rmn model shown by the dashed line as an example, and the method of the present invention is used to select the optimal harmonic order. Setting the dimension d=2m of the phase screen and the outer dimension L of the atmospheric turbulence 0 =10m, integrated power ratio α Φ ＝0.99。
2. According to the integrated power ratio alpha Φ The steps shown in the flow chart of figure 1 are carried out to obtain the preliminary optimal harmonic frequency p in_optimal ＝2.8419。
3. According to the actual conditions, p optimal And (5) performing approximate rounding to obtain:
(1) when extremely high accuracy (not lower than the running speed) is required for the phase screen, the final optimum harmonic order is p optimal ＝3；
(2) When the requirement on the accuracy of the phase screen is lower than the requirement on the running speed, the final optimal harmonic frequency is p optimal ＝2。
4. To verify p optimal When the corrected von K rm model is adopted, the phase structure function of the phase screen generated by different harmonic frequencies is compared with the theoretical value of the phase structure function, and the result is shown in the figure 3 (a); the relative error function results between the phase structure function of the phase screen and the theoretical value of the phase structure function generated by the different harmonic orders are shown in fig. 3 (b). As is apparent from fig. 3 (a) and fig. 3 (b), the phase structure function of the generated phase screen rapidly approaches the theoretical value of the phase structure function with the increase of two harmonics, and the relative error between the two harmonics also rapidly decreases; the addition of more harmonics does not seem to cause further improvement of the phase structure function and the relative error function, but it can be seen from the enlarged view of fig. 3 (b) that the relative error corresponding to the addition of the third harmonic is reduced by about 0.2% compared to the relative error corresponding to the addition of the second harmonic, i.e. there is still a certain improvement; however, the improvement effect is hardly seen by adding more harmonics. Therefore, when the phase screen needs extremely high accuracy, the optimal harmonic frequency should be selected to be p optimal =3; when the accuracy requirement of the phase screen is lower than the operation speed requirement, the optimal harmonic frequency is selected to be p optimal =2. This is consistent with the results of the calculations of the invention, thus verifying the accuracy of the method of the invention.
Claims (2)
1. The method is characterized in that initial conditions are set, a comprehensive power ratio is selected, initial optimal harmonic frequencies are calculated according to the initial conditions and the comprehensive power ratio, and the initial optimal harmonic frequencies are approximately rounded according to actual conditions to obtain final optimal harmonic frequencies; the selection method comprises the following specific steps:
a. setting initial conditions, selecting comprehensive power ratio
：
(1) The initial conditions include: size of phase screenDExternal dimensions of atmospheric turbulence
；
(2) The ratio of the integrated power is selected to be,
the value range of (2) is [0,1 ]]；
b. Based on the set initial conditions and the selected integrated power ratio
Calculating preliminary optimal harmonic order +.>
：
；
c. According to the actual conditions
Performing approximate rounding to obtain final optimal harmonic order +.>
：
(1) When the requirement on the accuracy of the phase screen is not lower than the requirement on the running speed, the final optimal harmonic frequency is as follows:
；
(2) when the requirement on the accuracy of the phase screen is lower than the requirement on the running speed, the final optimal harmonic frequency is as follows:
。
2. according to claimThe method for selecting optimal harmonic frequencies for simulating an atmospheric turbulence phase screen as recited in claim 1, wherein said integrated power ratio is set to
。
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811297218 | 2018-11-01 | ||
| CN2018112972182 | 2018-11-01 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109800543A CN109800543A (en) | 2019-05-24 |
| CN109800543B true CN109800543B (en) | 2023-06-16 |
Family
ID=66563881
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910234014.2A Active CN109800543B (en) | 2018-11-01 | 2019-03-26 | Optimal harmonic frequency selection method for simulating atmospheric turbulence phase screen |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109800543B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6023977A (en) * | 1997-08-01 | 2000-02-15 | Acuson Corporation | Ultrasonic imaging aberration correction system and method |
| CN102164004A (en) * | 2011-03-02 | 2011-08-24 | 中国科学院上海光学精密机械研究所 | Method for fast simulating phase screen distorted by time-varying turbulence and used for light-spot positioning |
| CN103605860A (en) * | 2013-11-28 | 2014-02-26 | 中国科学院软件研究所 | Non-ideal light source simulation method based on equivalent phase screen method |
| CN106644104A (en) * | 2016-10-13 | 2017-05-10 | 哈尔滨工业大学 | Phase screen modeling method for discrete raindrop media based on spectral inversion method |
-
2019
- 2019-03-26 CN CN201910234014.2A patent/CN109800543B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6023977A (en) * | 1997-08-01 | 2000-02-15 | Acuson Corporation | Ultrasonic imaging aberration correction system and method |
| CN102164004A (en) * | 2011-03-02 | 2011-08-24 | 中国科学院上海光学精密机械研究所 | Method for fast simulating phase screen distorted by time-varying turbulence and used for light-spot positioning |
| CN103605860A (en) * | 2013-11-28 | 2014-02-26 | 中国科学院软件研究所 | Non-ideal light source simulation method based on equivalent phase screen method |
| CN106644104A (en) * | 2016-10-13 | 2017-05-10 | 哈尔滨工业大学 | Phase screen modeling method for discrete raindrop media based on spectral inversion method |
Non-Patent Citations (1)
| Title |
|---|
| Numerical modeling of atmospherically perturbed phase screens: new solutions for classical fast Fourier transform and Zernike methods;Marcel Carbillet et al.;《APPLIED OPTICS》;20101101;第47-49页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109800543A (en) | 2019-05-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Zhou et al. | Large-eddy simulation of the stable boundary layer with explicit filtering and reconstruction turbulence modeling | |
| US10439594B2 (en) | Actually-measured marine environment data assimilation method based on sequence recursive filtering three-dimensional variation | |
| Daniels et al. | A new vertical grid nesting capability in the Weather Research and Forecasting (WRF) Model | |
| Troldborg | Actuator line modeling of wind turbine wakes | |
| Laporte et al. | Direct numerical simulations of the elliptic instability of a vortex pair | |
| Kim et al. | An advanced synthetic eddy method for the computation of aerofoil–turbulence interaction noise | |
| KR101332559B1 (en) | Numerical simulation system and method for atmospheric wind flow by computational fluid dynamics | |
| Chen et al. | Numerical dispersion analysis and key parameter selection in Laguerre-FDTD method | |
| CN107657075B (en) | The Region Decomposition FInite Element of Darcy velocity at simulated groundwater dielectric interface | |
| Aboshosha et al. | LES of ABL flow in the built-environment using roughness modeled by fractal surfaces | |
| Rieper et al. | Range of validity of an extended WKB theory for atmospheric gravity waves: One-dimensional and two-dimensional case | |
| CN115062563A (en) | Wind turbine three-dimensional wake flow wind speed calculation method based on space change | |
| CN109800543B (en) | Optimal harmonic frequency selection method for simulating atmospheric turbulence phase screen | |
| Deng et al. | An improved inflow turbulence generator for large eddy simulation evaluation of wind effects on tall buildings | |
| Zhang et al. | Derivation and verification of three-dimensional wake model of multiple wind turbines based on super-Gaussian function | |
| Danioux et al. | Near-inertial-wave scattering by random flows | |
| Han | A two-time-level split-explicit ocean circulation model (MASNUM) and its validation | |
| CN104933261A (en) | High efficient sequential maximin latin hypercube design method | |
| CN106156475A (en) | The Transient Electromagnetic characteristic rapid extracting method of Electrically large size object | |
| CN103997047A (en) | Subsynchronous oscillation modeling method for point-to-network system | |
| Ji et al. | An inflow turbulence generation method for large eddy simulation and its application on a standard high-rise building | |
| Zhang et al. | Multiscale analysis of a very long wind turbine wake in an atmospheric boundary layer | |
| CN115310388A (en) | Method for calculating three-dimensional asymmetric double-Gaussian wake flow wind speed of wind turbine with space change | |
| Yaremchuk et al. | On the renormalization of the covariance operators | |
| CN104374546A (en) | Universal atmosphere turbulence phase screen design method based on diffractive optical element |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |