Data conversion method for cylindrical flow-induced noise in air and water media

Abstract

The invention discloses a data conversion method for cylindrical flow-induced noise in air and water media, and the method comprises the steps: fitting a cylindrical surface semi-empirical sound source model through solving a cylindrical sound source-far field flow-induced noise dimensionless transfer function under a low Mach number, and building a data conversion method model for the cylindrical flow-induced noise in the air and water media; the method realizes accurate conversion of cylindrical flow induced noise data in air and water media, has the characteristic of accurate and reliable conversion, widens the application range of the cylindrical flow induced noise data, and provides a new technical means for underwater acoustic measurement and noise control.

Description

Technical Field

[0001] The invention relates to the field of aerodynamic noise, and in particular to a data conversion method for noise caused by cylindrical flow in air and water media. Background Art

[0002] The problem of cylindrical flow-induced noise is widely present in the fields of aerospace, navigation, hydraulic engineering, wind engineering, etc. The cylindrical structures such as the cable mooring rods and antenna protrusions of underwater vehicles will cause obvious flow-induced noise, and this type of cylindrical flow-induced noise is an important component of the hydrodynamic noise of the vehicle. When the fluid flows through the surface of the cylinder, the alternating vortex behind the cylinder will produce positive and negative circulation on the surface of the cylinder, causing periodic pressure fluctuations, which is a typical dipole sound source.

[0003] Conventional research methods for hydrodynamic noise include water tunnel tests and self-propelled model tests. The relatively small scale of the water tunnel test platform and the large background noise, as well as the large interference of the external natural environment in field tests, have limited the development of related mechanism research and noise control technology. When the Mach number of air is less than 0.3, the compressibility effect can be ignored, and it has a certain physical similarity with the water medium, which lays the foundation for conducting hydrodynamic noise test research in wind tunnels. In addition, acoustic wind tunnels also have the advantages of large scale, low background noise, rich testing methods, and low test costs. Using acoustic wind tunnels to study cylindrical flow-induced noise is a feasible and effective research method.

[0004] According to the current research progress, the conversion of flow-induced noise on the cylindrical surface between two media is still limited to the comparative analysis of experimental data of the steady mechanical properties of fixed models and the unsteady mechanical properties of periodic motion models. There is no mature research and solution for the unsteady characteristics of fixed models (such as the pulsating pressure on the model surface, which mainly reflects the characteristics of the sound source) and the conversion of far-field flow-induced noise in air and water. The flow-induced noise data in air and water cannot be converted to each other. The existing theory cannot convert the cylindrical flow-induced noise in the wind tunnel to the cylindrical flow-induced noise underwater. Summary of the invention

[0005] The present invention proposes a data conversion method for cylindrical flow-induced noise in air and water media, which is used to achieve: Purpose 1: To convert the noise caused by a cylindrical flow at a certain velocity in the air to the noise caused by a cylindrical flow at a certain velocity underwater; Purpose 2: To convert the flow noise caused by a cylindrical flow at a certain velocity underwater into the flow noise caused by a cylindrical flow at a certain velocity in the air; Purpose 3: Convert the cylindrical flow-induced noise at a certain flow velocity in air / water to the cylindrical flow-induced noise at another flow velocity.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A method for converting noise caused by cylindrical flow in air and water medium comprises the following steps: Step 1: Obtain the dimensionless transfer function of cylindrical sound source-far-field flow-induced noise at low Mach number; By non-dimensionalizing the acoustic wave equation, the dimensionless acoustic wave equation with the cylindrical surface boundary conditions introduced is solved, and the mathematical relationship between the pulsating pressure field on the cylindrical surface and the far-field sound field is established. Finally, the dimensionless transfer function of the cylindrical sound source-far-field noise is derived.

[0007] Step 2: Fitting the semi-empirical sound source model of the cylindrical surface; Through the cylindrical potential flow theory, the mechanism of the pulsating pressure on the cylindrical surface is explained, the intrinsic connection between the cylindrical wake field and the pulsating pressure field is revealed, and the preliminary sound source expression function form of the cylindrical model is obtained. According to experimental measurements and high-precision numerical simulations, the semi-empirical parameters in the preliminary sound source expression function are fitted, and finally the semi-empirical sound source model of the cylindrical surface is obtained.

[0008] Step 3: Combining the cylindrical semi-empirical sound source model with the dimensionless transfer function of the sound source-far-field noise to obtain the cylindrical radiated noise power spectrum, the sound pressure level model is used to establish a data conversion model for cylindrical flow-induced noise in air and water media; the model is as follows:

[0009] Among them: subscripts 1 and 2 represent two media or different working conditions of the same medium, represents the flow-induced noise sound pressure level of the cylinder, is the fluid density, is the incoming flow velocity, is the cylinder diameter, is the cylindrical extension, is the speed of sound in the fluid, is the Reynolds number, is the Mach number, is the Strouhal number, is the spectral angular frequency, is the distance between the noise receiving point and the center of the cylinder, It is the angle between the straight line perpendicular to the plane formed by the incoming flow and the span direction and the straight line from the sound source receiving point to the center of the cylinder. The angle between the cylinder span straight line and the straight line from the sound source receiving point to the center of the cylinder is the root mean square value of the dimensionless pulsating pressure on the cylindrical surface, It is a function related to the sound source's sound generation efficiency.

[0010] In the above technical solution, the following steps are included: S1: Obtain the radiated noise of the cylinder in air and water when the cylinder Reynolds number ranges from 21500 to 80000 and the Mach number is less than 0.3; S2: The FW-H equation is dimensionless by introducing characteristic velocity, characteristic scale, and characteristic frequency related parameters; S3: Introduce the free space Green's function into the equation obtained in S2, bring in the cylindrical surface boundary conditions including the cylindrical diameter and the extension, and calculate the cylindrical sound source and far-field noise transfer function; S4: Process the time domain signal of the pulsating pressure on the cylindrical surface to obtain the correlation scale, characteristic frequency, and root mean square of the pulsating pressure flow direction and span direction, and fit the semi-empirical sound source model; S5: Combine the far-field noise transfer function in S3 with the semi-empirical sound source model in S4 to obtain the sound source sound generation efficiency correlation function; S6: The power spectrum of the cylindrical radiation noise with respect to the Reynolds number, Strouhal number and Mach number is calculated by using the sound source sound generation efficiency related function in S5 and the characteristic velocity, characteristic scale and characteristic frequency related parameters in S2; S7: The power spectrum of the cylindrical radiation noise obtained in S6 is processed in combination with the sound pressure level parameters to establish a data conversion model for the cylindrical flow-induced noise in the air and water media.

[0011] In the above technical solution, the following steps are included: A1: Measure the cylindrical flow-induced noise in the air, obtain the cylindrical flow-induced noise time domain data, and record the initial data in the air at the same time; A2: Preprocess the initial data in A1 to obtain the noise parameters caused by the cylindrical flow in the air; A3: Substitute the initial data in the air in A1 and the cylindrical flow-induced noise parameters in A2 into the sound source sound generation efficiency correlation function to obtain the sound source sound generation efficiency correlation function result in the air; A4: Determine the initial data of the cylindrical flow-induced noise that needs to be converted in the water medium; A5: Preprocess the underwater initial data obtained in A4 to obtain the noise parameters caused by underwater cylindrical flow; A6: Substitute the underwater initial data obtained in A4 and the underwater cylindrical flow-induced noise parameters obtained in A5 into the sound source sound generation efficiency correlation function to obtain the result of the underwater sound source sound generation efficiency correlation function; A7: Input all the parameters obtained in A1-A6 into the conversion model of cylindrical flow-induced noise in air and water media to obtain the sound pressure level of underwater cylindrical flow-induced noise, thus completing the data conversion of cylindrical flow-induced noise in air and water media.

[0012] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: The present invention realizes the accurate conversion of cylindrical flow-induced noise data in air and water media by establishing a conversion model, has the characteristics of accurate and reliable conversion, broadens the application scope of cylindrical flow-induced noise data, and provides a new technical means for underwater acoustic measurement and noise control BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 It is a schematic diagram of the cylindrical model; Figure 2 This is a schematic diagram comparing this scheme with actual measurements. DETAILED DESCRIPTION

[0014] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0015] Any feature disclosed in this specification (including any additional claims, abstract and drawings), unless otherwise stated, may be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0016] This embodiment is carried out when the cylindrical Reynolds number ranges from 21500 to 80000 and the Mach number is less than 0.3. This Reynolds number range is within the Reynolds number self-calibration region, and the influence of the Reynolds number on the cylindrical flow state is relatively small.

[0017] Measure the cylindrical flow-induced noise in the air, obtain the time domain data of the cylindrical flow-induced noise, and obtain the initial data in the air: air density , flow rate, cylinder diameter , cylindrical extension , and the distance between the receiving point and the center of the cylinder.

[0018] The initial data is preprocessed to obtain the key parameters of the noise caused by cylindrical flow in air: Strouhal number ,Mach number , Reynolds number , spectrum corner frequency , the root mean square value of the dimensionless pulsating pressure on the surface , Sound pressure level of noise caused by cylindrical flow .

[0019] Substitute the initial data in the air and the key parameters in the air into the sound source sound efficiency correlation function to obtain the result of the sound source sound efficiency correlation function in the air, as follows:

[0020] in, , .

[0021] Determine the initial data of the cylindrical flow noise required to be converted in the water medium, the underwater fluid density , flow rate, cylinder diameter , cylindrical extension , and the distance between the receiving point and the center of the cylinder.

[0022] The initial underwater data is preprocessed to obtain the key parameters of underwater cylindrical flow-induced noise: Strouhal number ,Mach number , Reynolds number , spectrum corner frequency .

[0023] The obtained underwater initial data and underwater key parameters are substituted into the sound source sound generation efficiency correlation function to obtain the underwater sound source sound generation efficiency correlation function result.

[0024] All the parameters obtained are input into the conversion formula of cylindrical flow-induced noise in air and water media to obtain the underwater cylindrical flow-induced noise sound pressure level. , complete the data conversion of cylindrical flow-induced noise in air and water media,

[0025] Among them: subscripts 1 and 2 represent two media or different working conditions of the same medium, represents the flow-induced noise sound pressure level of the cylinder, is the fluid density, is the incoming flow velocity, is the cylinder diameter, is the cylindrical extension, is the speed of sound in the fluid, is the Reynolds number, is the Mach number, is the Strouhal number, is the spectral angular frequency, is the distance between the noise receiving point and the center of the cylinder, It is the angle between the straight line perpendicular to the plane formed by the incoming flow and the span direction and the straight line from the sound source receiving point to the center of the cylinder. is the angle between the cylinder span straight line and the straight line from the sound source receiving point to the center of the cylinder, is the root mean square value of the dimensionless pulsating pressure on the cylindrical surface, It is a function related to the sound source's sound generation efficiency.

[0026] The converted sound pressure level of the cylindrical flow noise in the air is compared with the sound pressure level of the cylindrical flow noise obtained in the underwater test. The results are as follows: Figure 2As shown in the figure. The conversion result in the figure is the noise sound pressure level of the cylinder with a diameter of 10mm, a length of 50mm, and a receiving point at 1.5m when the wind speed in the air is 70m / s, which is converted to the noise sound pressure level of the same cylinder when the water speed is 2m / s underwater. The test result in the figure is the experimentally measured noise sound pressure level when the water speed is 2m / s underwater, with a cylinder diameter of 10mm, a length of 50mm, and a receiving point at 1.5m. By comparison, it can be found that the converted result is basically consistent with the experimentally measured noise sound pressure level result, with a maximum peak difference of 1.88dB, indicating that the converted result is relatively accurate and reliable.

[0027] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A method for converting the noise caused by cylindrical flow in air and water medium, characterized in that The following steps are involved: Step 1: Obtain the dimensionless transfer function of cylindrical sound source-far-field flow-induced noise at low Mach number; Step 2: Fitting the semi-empirical sound source model of the cylindrical surface; Step 3: Combine steps 1 and 2 to obtain the power spectrum of the cylindrical radiation noise, and use the sound pressure level model to establish the data conversion model of the cylindrical flow-induced noise in the air and water media as follows: , where: subscripts 1 and 2 represent two media or different working conditions of the same medium, represents the flow-induced noise sound pressure level of the cylinder, is the fluid density, is the incoming flow velocity, is the cylinder diameter, is the cylindrical extension, is the speed of sound in the fluid, is the Reynolds number, is the Mach number, is the Strouhal number, is the spectral angular frequency, is the distance between the noise receiving point and the center of the cylinder, It is the angle between the straight line perpendicular to the plane formed by the incoming flow and the span direction and the straight line from the sound source receiving point to the center of the cylinder. The angle between the cylinder span straight line and the straight line from the sound source receiving point to the center of the cylinder is the root mean square value of the dimensionless pulsating pressure on the cylindrical surface, It is a function related to the sound source's sound generation efficiency.

2. A method for converting data of cylindrical flow-induced noise in air and water media according to claim 1, characterized in that The following steps are involved: S1: Obtain the radiated noise of the cylinder in air and water when the cylinder Reynolds number ranges from 21500 to 80000 and the Mach number is less than 0.3; S2: The FW-H equation is dimensionless by introducing characteristic velocity, characteristic scale, and characteristic frequency related parameters; S3: Introduce the free space Green's function into the equation obtained in S2, bring in the cylindrical surface boundary conditions including the cylindrical diameter and the extension, and calculate the cylindrical sound source and far-field noise transfer function; S4: Process the time domain signal of the pulsating pressure on the cylindrical surface to obtain the correlation scale, characteristic frequency, and root mean square of the pulsating pressure flow direction and span direction, and fit the semi-empirical sound source model; S5: Combine the far-field noise transfer function in S3 with the semi-empirical sound source model in S4 to obtain the sound source sound generation efficiency correlation function; S6: The power spectrum of the cylindrical radiation noise with respect to the Reynolds number, Strouhal number and Mach number is calculated by using the sound source sound generation efficiency related function in S5 and the characteristic velocity, characteristic scale and characteristic frequency related parameters in S2; S7: The power spectrum of the cylindrical radiation noise obtained in S6 is processed in combination with the sound pressure level parameters to establish a data conversion model for the cylindrical flow-induced noise in the air and water media.

3. The method for converting the noise caused by cylindrical flow in air and water medium according to claim 2 is characterized in that The following steps are involved: A1: Measure the cylindrical flow-induced noise in the air, obtain the cylindrical flow-induced noise time domain data, and record the initial data in the air at the same time; A2: Preprocess the initial data in A1 to obtain the noise parameters caused by the cylindrical flow in the air; A3: Substitute the initial data in the air in A1 and the cylindrical flow-induced noise parameters in A2 into the sound source sound generation efficiency correlation function to obtain the sound source sound generation efficiency correlation function result in the air; A4: Determine the initial data of the cylindrical flow-induced noise that needs to be converted in the water medium; A5: Preprocess the underwater initial data obtained in A4 to obtain the noise parameters caused by underwater cylindrical flow; A6: Substitute the underwater initial data obtained in A4 and the underwater cylindrical flow-induced noise parameters obtained in A5 into the sound source sound generation efficiency correlation function to obtain the result of the underwater sound source sound generation efficiency correlation function; A7: Input all the parameters obtained in A1-A6 into the conversion model of cylindrical flow-induced noise in air and water media to obtain the sound pressure level of underwater cylindrical flow-induced noise, thus completing the data conversion of cylindrical flow-induced noise in air and water media.

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