Non-stationary turbulent wind field large vortex simulation inlet synthesis method and device

Abstract

The invention discloses a large-vortex simulation inlet synthesis method and device for a non-stationary turbulent wind field. The method comprises the following steps: simulating a non-stationary time-varying average wind speed by adopting a continuous and derivable sine wave; a PRFG3 random flow method is adopted to generate three-dimensional anisotropic turbulence with a specific vertical wind shear parameter, turbulence level and turbulence integral scale; and superposing the sine wave and the random flow to generate a non-stationary turbulent wind field with non-stationary parameters capable of being accurately adjusted. By the adoption of the technical scheme, the sudden rise and sudden drop of the time-varying average wind speed and the vertical wind shear characteristic can be accurately simulated, the time-varying turbulivity and the integral scale of the pulsation component can also be accurately simulated, and the method can be used for large eddy simulation research of specific strong wind such as strong typhoon, thunderstorm wind and downburst.

Description

Technical Field

[0001] The invention belongs to the technical field of computational fluid dynamics, and in particular relates to a method and a device for synthesizing an inlet of a large eddy simulation of a non-steady turbulent wind field. Background Art

[0002] With global warming, strong typhoons, thunderstorms, downbursts and other special strong winds occur frequently, with strong short-term sudden rise and fall in the horizontal direction, showing strong non-stationary characteristics, and significant wind shear effect in the vertical direction. The load effect of special strong winds is significantly higher than that of traditional stable wind fields, and the relevant wind resistance design specifications have not yet been perfected, which seriously threatens the wind resistance safety of large-span bridges and new energy structures such as large offshore wind turbines and flexible photovoltaic brackets. At present, the research on non-stationary strong winds mainly relies on active wind tunnel tests, which require expensive impact jets or active turbulence generation devices. It is urgent to develop a CFD simulation method for non-stationary shear wind fields.

[0003] Large eddy simulation (LES) is widely used in the field of computational fluid dynamics due to its advantages in both computational accuracy and cost. However, the current LES research on non-steady wind loads still continues the impact jet model, which requires more than one million auxiliary grids to generate non-steady wind fields, and it is difficult to accurately control non-steady strong wind parameters such as acceleration factor, vertical wind shear factor, time-varying turbulence intensity and turbulence integral scale, which limits the in-depth study of the effects of non-steady strong wind loads. The LES inlet turbulence synthesis method can significantly reduce the computational cost and better control the turbulence characteristics. However, there are few studies on the LES inlet synthetic turbulence for non-steady wind fields, and the traditional random flow generation synthesis method can only consider the inlet of a steady wind field. Therefore, it is urgent to develop an efficient and accurate LES inlet method for non-steady vertical shear wind fields. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and device for synthesizing an inlet of a non-stationary turbulent wind field large eddy simulation based on a sine wave superimposed random flow.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A method for synthesizing an inlet for large eddy simulation of a non-stationary turbulent wind field, comprising:

[0007] Step S1, using a continuously differentiable sine wave to simulate a time-varying non-stationary average wind speed;

[0008] Step S2: Using PRFG 3 The random flow method generates three-dimensional anisotropic turbulence with specific vertical wind shear parameters, turbulence intensity and turbulence integral scale;

[0009] Step S3: Superimpose the sine wave and the random flow to generate a non-stationary turbulent wind field with precisely adjustable non-stationary parameters.

[0010] Preferably, in step S1, a non-stationary sine oncoming flow is superimposed on the basis of a fixed uniform oncoming flow, and the oncoming flow is continuously differentiable to avoid sudden wind speed fluctuations. The calculation formula of this wind field is:

[0011]

[0012] where U(t) is a three-dimensional time-varying mean wind speed vector matrix, n is the number of terms of the superimposed sine wave, a i , b i and c i are the parameters of each term of the superimposed sine wave, and t is time.

[0013] Preferably, in step S2, anisotropic turbulence is generated based on the PRFG 3 method. A vertical wind shear turbulent wind field with a specific wind profile and turbulence intensity profile is achieved by introducing a weighting function and a phase difference. Linear convection based on the time-averaged velocity is used to approximate the momentum balance, and the velocity field satisfies the following equation:

[0014]

[0015] where u = [u, v, w] T is a three-dimensional pulsating wind speed vector matrix, x = [x, y, z] is a three-dimensional coordinate vector, N is the number of sampling wave vectors, M is the number of turbulence source vectors, p n,m and q n,m are random amplitude vector matrices, k n,m is a random wave number matrix, ω n,m is the random pulsating wind circular frequency, ψ n,m is the phase shift, w m (x) is the weighting function of each turbulence source, and (·) T is the transpose operator.

[0016] Preferably, it further includes: correcting the velocity components located on the inlet plane based on a variable inflow correction method to alleviate the induced spurious pressure fluctuations.

[0017] The present invention also provides a large eddy simulation inlet synthesis device for a non-stationary turbulent wind field, including:

[0018] A first calculation module for simulating a time-varying non-stationary mean wind speed using a continuously differentiable sine wave;

[0019] A second calculation module for using PRFG 3The random flow method generates three-dimensional anisotropic turbulence with specific vertical wind shear parameters, turbulence intensity, and turbulence integral scale;

[0020] The third calculation module is used to superimpose a sine wave and a random flow to generate a non-stationary turbulent wind field with precisely adjustable non-stationary parameters.

[0021] Preferably, the first calculation module is used to superimpose a non-stationary sine incoming flow on the basis of a fixed uniform incoming flow, and the incoming flow is continuously differentiable to avoid sudden wind speed fluctuations. The calculation formula of this wind field is:

[0022]

[0023] where U(t) is a three-dimensional time-varying mean wind speed vector matrix, n is the number of terms of the superimposed sine wave, a i , b i and c i are the parameters of each term of the superimposed sine wave, and t is time.

[0024] Preferably, the second calculation module is used to generate anisotropic turbulence based on the PRFG 3 method. By introducing a weighting function and a phase difference, a vertical wind shear turbulent wind field with a specific wind profile and turbulence intensity profile is realized. The linear convection based on the time-averaged velocity is used to approximate the momentum balance, and the velocity field satisfies the following equation:

[0025]

[0026] where u = [u, v, w] T is a three-dimensional pulsating wind speed vector matrix, x = [x, y, z] is a three-dimensional coordinate vector, N is the number of sampling wave vectors, M is the number of turbulence source vectors, p n,m and q n,m are random amplitude vector matrices, k n,m is a random wave number matrix, ω n,m is the random pulsating wind circular frequency, ψ n,m is the phase shift, w m (x) is the weighting function of each turbulence source, and (·) T is the transpose operator.

[0027] Preferably, it further includes: a fourth calculation module, which is used to correct the velocity components located on the inlet plane based on the variable inflow correction method to alleviate the induced false pressure fluctuations.

[0028] The present invention first simulates the non-stationary mean wind speed and the vertical wind shear through a sine wave, and adopts PRFG 3Anisotropic turbulence is achieved, and then the two are superimposed to achieve a non-stationary turbulent wind field. Finally, the VBIC method is used to reduce the pulsating false static pressure fluctuation at the inlet. The present invention can not only accurately simulate the sudden rise and fall in the horizontal direction and the vertical wind shear characteristics, but also accurately adjust the time-varying turbulence intensity and integral scale. The present invention can be used for large-eddy inlet simulation of non-stationary strong typhoons, thunderstorms, and downbursts. Compared with the large-eddy simulation of impinging jets, the proposed method significantly reduces the computational cost and improves the simulation accuracy, and has high application value in the fields of wind engineering of long-span bridges, photovoltaic wind resistance, and offshore wind power. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0030] Figure 1 Schematic flow chart of the large-eddy simulation inlet synthesis method for the non-stationary turbulent wind field of the present invention;

[0031] Figure 2 Schematic diagram of the large-eddy simulation calculation domain and grid division of the present invention (unit: m), where (a) is the schematic diagram of the calculation domain and (b) is the schematic diagram of the grid used;

[0032] Figure 3 Schematic diagram of the large-eddy simulation process and results of the non-stationary wind field generated in Example 1 of the present invention;

[0033] Figure 4 Schematic diagram of the structural measurement point layout of the cable-stayed bridge in the embodiment of the present invention (unit: cm);

[0034] Figure 5 Comparison diagram of the large-eddy simulation and measured curves of the actual non-stationary strong wind of the bridge in Example 3 and the non-stationary strong wind with vertical wind shear in Example 4 of the present invention, where (a) is the wind speed time history curve and (b) is the measured downburst wind profile at Andersen Air Force Base (AAFB) in the United States. Detailed Embodiments

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] To make the above objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Example 1:

[0038] The embodiment of the present invention provides a large-eddy simulation inlet synthesis method for non-stationary turbulent wind fields. A continuously differentiable sine wave is used to simulate the time-varying non-stationary mean wind speed, and a prescribed-wavelength random flow generator 3 (Prescribed-wavelengthRandom Flow Generator 3 , PRFG 3 ) random flow method is used to generate three-dimensional anisotropic turbulence with specific vertical wind shear parameters, turbulence intensity, and turbulence integral scale, and the VBIC method is used to reduce the common spurious pressure fluctuations when using synthetic inlet flows. By superimposing the sine wave and the random flow, a non-stationary turbulent wind field with precisely adjustable non-stationary parameters can be generated. The wind field of the embodiment of the present invention is generated in the computational domain grids shown in (a) and (b) as shown in Figure 2 . As shown in Figure 1 , the large-eddy simulation inlet synthesis of the non-stationary turbulent wind field includes the following steps:

[0039] Step 1: Analysis of measured non-stationary strong wind characteristic parameters. Based on EMD decomposition, time-varying mean wind speed, turbulence intensity, and turbulence integral scale parameters are obtained. Specifically:

[0040]

[0041] Where: I(n) is the input signal, IMF m (n) is the intrinsic mode function of M th , and Res M (n) is the residual.

[0042] Step 2: Sine wave fitting modeling of non-stationary time-varying mean wind speed. On the basis of a fixed uniform incoming flow, a non-stationary sine incoming flow is superimposed. This incoming flow needs to be continuously differentiable to avoid sudden wind speed fluctuations. The calculation formula of this wind field is:

[0043]

[0044] Where: U(t) is the three-dimensional time-varying mean wind speed vector matrix, n is the number of superimposed sine waves, a i , b i , and c i are the parameters of each superimposed sine wave, and t is the time.

[0045] Step 3. Apply vertical wind shear: Based on the measured non-stationary strong wind profile data, compile the wind profile expression of the wind speed varying with height into the program. The calculation formula of this profile is:

[0046]

[0047] Where: U v is the wind speed varying with height, y m is the reference height, U m is the wind speed at the reference height, is the relationship formula between any height and the reference height.

[0048] Step 4. Generate anisotropic turbulence based on the PRFG 3 method. By introducing a weighting function and a phase difference, a vertical wind shear turbulent wind field with a specific wind profile and turbulence intensity profile is realized. The linear convection based on the time-averaged velocity is used to approximate the momentum balance, ensuring that the synthesized turbulent field conforms to the Navier-Stokes equation as much as possible near the time-averaged condition. The specific velocity field needs to satisfy the following equations:

[0049]

[0050] Where: u = [u, v, w] T is the three-dimensional pulsating wind speed vector matrix, x = [x, y, z] is the three-dimensional coordinate vector, N is the number of sampling wave vectors, M is the number of turbulence source vectors, p n,m and q n,m are the random amplitude vector matrices, k n,m is the random wave number matrix, ω n,m is the random pulsating wind circular frequency, ψ n,m is the phase shift, w m (x) is the weighting function of each turbulence source, (·) T is the transpose operator.

[0051] Step 5. Superimpose the non-stationary time-varying mean wind speed and random turbulence. For the non-stationary incoming flow, it is necessary to superimpose the pulsating component of the velocity field under the uniform flow in the x direction. Therefore, the velocity field under the non-stationary incoming flow is calculated as:

[0052]

[0053] Where: u n-s = [u n-s , v s , w s T is the three-dimensional synthesized velocity field of the non-stationary incoming flow.

[0054] ​Step 6: Preparation of the inlet for large-eddy simulation of non-stationary wind fields. By programming the above non-stationary turbulence theoretical formula in C++ using the open-source computational software OpenFOAM, precise adjustment of strong wind characteristics such as non-stationary acceleration time, turbulence intensity, and turbulence integral scale can be achieved.

[0055] Step 7: Correction of the spurious static pressure fluctuations at the inlet based on the Variationally Based Inflow Correction (VBIC) method. Since the synthetic turbulent flow field does not match the Navier-Stokes equations and the boundary conditions adjacent to the inlet region, spurious pressure fluctuations are caused. Based on the VBIC method, the velocity components on the inlet plane are corrected to mitigate the induced spurious pressure fluctuations. The calculation formula is:

[0056] u = u s + u c (6)

[0057] where: u is the corrected velocity field actually applied to the inlet region, and u c = [0, v c , w c T is the velocity correction term calculated to minimize the norm.

[0058] Example 2

[0059] The embodiment of the present invention provides a method for synthesizing the inlet of a non-stationary turbulent wind field based on the superposition of sine waves and random flows. The specific steps are as follows:

[0060] 1) Generate a sine-flow time-varying mean wind

[0061] For the applied sine incoming flow, the formula for the time-varying mean wind speed is as follows:

[0062]

[0063] where: U(t) is the time-varying mean wind speed in the x direction, U s is the starting wind speed, U e is the cut-off wind speed, t s is the start time of acceleration, and t e is the end time of acceleration. In this example, set t s = 2 s, t e = 4 s, U s = 3 m / s, and U e = 6 m / s.

[0064] 2) Generate pulsating turbulence

[0065] ​For the applied pulsating turbulence, the wind speed expression is as shown in Equation (4), where the adopted average wind speed is U = 4.5 m / s.

[0066] 3) Superposition of sine flow and pulsating turbulence

[0067] The superposition process and results are as Figure 3 shown.

[0068] Example 3:

[0069] Based on the measured non-stationary strong wind data of the cable-stayed bridge health monitoring system in Example 2, large-eddy inlet simulation is realized, and the specific steps are as follows:

[0070] 1) Cable-stayed bridge health monitoring system

[0071] Taking a certain super-large cable-stayed bridge as the research object, as Figure 4 shown, the total length of the bridge is 1339 m, the main span is 618 m, it is a double-tower and double-cable-plane composite girder cable-stayed bridge, a semi-floating system structure with the tower and girder separated, the cable tower is a diamond-shaped variable cross-section tower with a height of 216 m; the main span main girder adopts a steel box girder, the side span main girder adopts a concrete girder, and the main bridge deck width is 31 m.

[0072] For the arrangement of wind speed monitoring points and real-time signal acquisition, three-dimensional anemometers are installed at the steel box girder section and the corresponding measuring points of the main tower at the positions as Figure 4 shown, for measuring the real-time changes of the wind speed at different cross-section positions of the cable-stayed bridge main girder and at different heights of the main tower.

[0073] 2) Analysis of the characteristics of measured non-stationary strong wind samples

[0074] By analyzing the wind field monitoring data, non-stationary strong wind samples are selected, and wind parameters such as time-varying average wind speed, turbulence intensity, turbulence integral scale, wind yaw angle, wind attack angle, and power spectrum are analyzed.

[0075] 3) Time-varying average wind of measured non-stationary strong wind

[0076] The time-varying average wind of the measured non-stationary strong wind is expressed by the following formula:

[0077]

[0078] In this example, set a 1 = 16.34, a 2 = 2.239, a 3 = 3.439, b 1 = 0.0329, b 2 = 0.185, b 3 = 0.102, c 1 = 0.178, c 2 = -3.577, c 3=-0.788.

[0079] 4) Measured non - stationary turbulent large - eddy simulation

[0080] The comparison between the measured non - stationary turbulent large - eddy simulation and the measurement is as Figure 5 shown in (a) and (b).

[0081] Example 4:

[0082] Based on Examples 2 and 3, a non - stationary turbulent wind field simulation of a downburst with vertical wind shear is realized. The specific steps are as follows:

[0083] 1) Selection of the downburst profile

[0084] Adopt the typical downburst wind profile of the Anderson Air Force Base (AAFB) in the United States. The relationship formula between any height and the reference height is:

[0085]

[0086] In the formula: γ is an empirical constant. In this example, γ = 0.261 is set, and y m = 10m.

[0087] 2) Generation of the downburst profile

[0088] Compile the wind parameters analyzed above and simulate the selected non - stationary turbulent wind field through a non - stationary prescribed - wavelength random flow generator 3 (PRFG 3 ). Calculate the wind parameters of the simulation results and compare them with those in the measured analysis to verify the accuracy of the simulation. The comparison between the large - eddy simulation of the measured non - stationary strong wind and the measured curve is as Figure 5 shown; the comparison between the large - eddy simulation of the measured downburst wind shear at the Anderson Air Force Base (AAFB) in the United States and the measurement is as Figure 5 shown.

[0089] Example 5:

[0090] The embodiment of the present invention also provides a non - stationary turbulent wind field large - eddy simulation inlet synthesis device, including:

[0091] The first calculation module is used to simulate the time - varying non - stationary mean wind speed by using a continuously differentiable sine wave;

[0092] The second calculation module is used to generate three - dimensional anisotropic turbulence with specific vertical wind shear parameters, turbulence intensity, and turbulence integral scale by using the PRFG 3 random flow method;

[0093] The third calculation module is used to superimpose the sine wave and the random flow to generate a non - stationary turbulent wind field with precisely adjustable non - stationary parameters.

[0094] As an implementation manner of an embodiment of the present invention, the first calculation module is used to superimpose a non-stationary sine oncoming flow on the basis of a fixed uniform oncoming flow, and the oncoming flow is continuously differentiable to satisfy that there is no sudden wind speed fluctuation. The calculation formula of this wind field is:

[0095]

[0096] where U(t) is a three-dimensional time-varying mean wind speed vector matrix, n is the number of terms of the superimposed sine wave, a i , b i and c i are the parameters of each superimposed sine wave, and t is time.

[0097] As an implementation manner of an embodiment of the present invention, the second calculation module is used to generate anisotropic turbulence based on the PRFG 3 method, and realize a vertical wind shear turbulent wind field with a specific wind profile and turbulence intensity profile by introducing a weighting function and a phase difference, and use linear convection based on the time-averaged velocity to approximate the momentum balance. The velocity field satisfies the following equation:

[0098]

[0099] where u = [u, v, w] T is a three-dimensional pulsating wind speed vector matrix, x = [x, y, z] is a three-dimensional coordinate vector, N is the number of sampling wave vectors, M is the number of turbulence source vectors, p n,m and q n,m are random amplitude vector matrices, k n,m is a random wave number matrix, ω n,m is the random pulsating wind circular frequency, ψ n,m is the phase shift, w m (x) is the weighting function of each turbulence source, and (·) T is the transpose operator.

[0100] As an implementation manner of an embodiment of the present invention, it further includes: a fourth calculation module, which is used to correct the velocity components located on the inlet plane based on the variable inflow correction method to alleviate the caused false pressure fluctuations.

[0101] The above-described embodiments are only descriptions of the preferred manners of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for synthesizing an inlet for large eddy simulation of a non-stationary turbulent wind field, characterized in that: include: Step S1, using a continuously differentiable sine wave to simulate a time-varying non-stationary average wind speed; Step S2: Using PRFG 3 The random flow method generates three-dimensional anisotropic turbulence with specific vertical wind shear parameters, turbulence intensity and turbulence integral scale; Step S3: superimpose the sine wave and the random flow to generate a non-stationary turbulent wind field whose non-stationary parameters can be precisely adjusted.

2. The inlet synthesis method for large eddy simulation of non-stationary turbulent wind field according to claim 1, characterized in that: In step S1, a non-stationary sinusoidal incoming flow is superimposed on a fixed uniform incoming flow, and the incoming flow is continuously divisible to ensure that there is no sudden wind speed fluctuation. The calculation formula of the wind field is: Among them, U(t) is the three-dimensional time-varying average wind speed vector matrix, n is the number of superimposed sine waves, and a i , b i and c i is the parameter of each superimposed sine wave, and t is the time.

3. The inlet synthesis method for large eddy simulation of non-stationary turbulent wind field according to claim 2, characterized in that: In step S2, based on PRFG 3 The method generates anisotropic turbulence. By introducing weighting functions and phase differences, a vertical wind shear turbulent wind field with a specific wind profile and turbulence intensity profile is realized. The linear convection based on the time-averaged velocity is used to approximate the momentum balance. The velocity field satisfies the following equation: Among them, u=[u,v,w] T is the three-dimensional fluctuating wind speed vector matrix, x = [x, y, z] is the three-dimensional coordinate vector, N is the number of sampled wave vectors, M is the number of turbulence source vectors, p n,m and q n,m is the random amplitude vector matrix, k n,m is the random wave number matrix, ω n,m is the circular frequency of random pulsating wind, ψ n,m is the phase shift, w m (x) is the weighting function for each turbulence source, (·) T is the transpose operator.

4. The inlet synthesis method for large eddy simulation of non-stationary turbulent wind field according to claim 3, characterized in that: Also includes: The variable-based inflow correction method modifies the velocity component located on the inlet plane to mitigate the induced spurious pressure fluctuations.

5. A large eddy simulation inlet synthesis device for non-steady turbulent wind field, characterized in that: include: The first calculation module is used to simulate the time-varying non-stationary average wind speed using a continuous and differentiable sine wave; The second calculation module is used to use PRFG 3 The random flow method generates three-dimensional anisotropic turbulence with specific vertical wind shear parameters, turbulence intensity and turbulence integral scale; The third calculation module is used to superimpose the sine wave and the random flow to generate a non-stationary turbulent wind field with precisely adjustable non-stationary parameters.

6. The inlet synthesis device for large eddy simulation of non-steady turbulent wind field according to claim 5, characterized in that: The first calculation module is used to superimpose a non-stationary sinusoidal flow on the basis of a fixed uniform flow. The flow is continuously divisible to ensure that there is no sudden wind speed fluctuation. The calculation formula of the wind field is: Among them, U(t) is the three-dimensional time-varying average wind speed vector matrix, n is the number of superimposed sine waves, and a i , b i and c i is the parameter of each superimposed sine wave, and t is the time.

7. The inlet synthesis device for large eddy simulation of non-steady turbulent wind field according to claim 6, characterized in that: The second calculation module is used based on PRFG 3 The method generates anisotropic turbulence. By introducing weighting functions and phase differences, a vertical wind shear turbulent wind field with a specific wind profile and turbulence intensity profile is realized. The linear convection based on the time-averaged velocity is used to approximate the momentum balance. The velocity field satisfies the following equation: Among them, u=[u,v,w] T is the three-dimensional fluctuating wind speed vector matrix, x = [x, y, z] is the three-dimensional coordinate vector, N is the number of sampled wave vectors, M is the number of turbulence source vectors, p n,m and q n,m is the random amplitude vector matrix, k n,m is the random wave number matrix, ω n,m is the circular frequency of random pulsating wind, ψ n,m is the phase shift, w m (x) is the weighting function for each turbulence source, (·) T is the transpose operator.

8. The inlet synthesis device for large eddy simulation of non-steady turbulent wind field according to claim 7, characterized in that: Also includes: The fourth calculation module is used to correct the velocity component located on the inlet plane based on the variable inflow correction method to alleviate the false pressure fluctuation caused.

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