A Method, Device and Storage Medium for Analyzing the Flow Noise at the Inlet and Outlet of a Gravity Cooling System

Abstract

The present invention discloses a method, device and storage medium for predicting the flow noise at the inlet and outlet of a gravity cooling system, including constructing a one-dimensional model of the internal flow domain components and a three-dimensional model of the external flow domain components of the gravity cooling system. Among them, the internal flow domain components are composed of an eccentric butterfly valve, a condenser and a connecting pipe. Nodes are set at the joints of each component in the one-dimensional model to obtain pressure information. The flow source is coupled with the coupling surface at the pipe inlet, and the pressure source is coupled with the coupling surface at the pipe outlet. The external flow domain components are composed of an underwater vehicle hull, an inlet and an outlet. In the three-dimensional model, the outlet and inlet of the open sea outlet are extended by 1 m at the same time, and the position 1 m away from the extended outlet and inlet of the open sea outlet is used as the coupling surface; set the flow field boundary conditions for one-dimensional-three-dimensional coupling calculation, construct a one-dimensional-three-dimensional coupling model of the gravity cooling system based on the coupling region data exchange, and perform one-dimensional-three-dimensional coupling flow field calculation; based on the fluid pulsation results obtained from the flow field calculation, perform sound field calculation. By applying the one-dimensional-three-dimensional coupling method in the gravity cooling system model, the present invention provides a new method for predicting the flow noise of the gravity cooling system, and at the same time saves computing resources and computing time.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater vehicles, and particularly relates to a method, device, and storage medium for analyzing the flow noise at the inlet and outlet of a gravity cooling system. Background Art

[0002] Modern underwater vehicles use a gravity cooling circulation system to provide cooling water for the condenser, which is simply referred to as a gravity cooling system. During navigation, the fluid flowing inside the pipeline of the gravity cooling system will generate flow noise and radiate outward from the sea outlet, directly affecting the marine ecological environment. The flow noise of the sea-connected pipeline of the gravity cooling system is an important noise source of the flow noise of the underwater vehicle. Effectively suppressing the radiation noise at the inlet and outlet of the sea-connected pipeline of the gravity cooling system is an important link to achieve low noise of the underwater vehicle.

[0003] As a sea-connected pipeline, the gravity cooling system generally consists of an inlet / outlet, valve / pump components, a condenser, a grille, and a fairing, etc. It is very important to comprehensively understand the generation, propagation process of the flow noise in the sea-connected pipeline of the gravity cooling system and the radiation characteristics at the inlet and outlet. For simulation research, considering the large scale and complex model of the gravity cooling system, a method is needed to reduce the calculation amount and simulation time.

[0004] Moreover, the internal flow noise of the gravity cooling system propagates the noise to the inlet and outlet through the fluid and directly radiates outward. It is relatively difficult to reduce this part of the noise, so it has become the focus of the current research on the noise radiation of the gravity cooling system. Summary of the Invention

[0005] Aiming at the defects existing in the above-mentioned prior art, the present invention provides a method, device, and storage medium for analyzing the flow noise at the inlet and outlet of a gravity cooling system. The method includes the following steps:

[0006] Determine the composition structure of the gravity cooling system of the underwater vehicle, including the underwater vehicle hull, inlet, outlet eccentric butterfly valve, condenser, and connecting pipe;

[0007] Construct a one-dimensional model of the internal flow domain components and a three-dimensional model of the external flow domain components of the gravity cooling system. Among them, the internal flow domain components are connected by an eccentric butterfly valve, a condenser, and a connecting pipe. Nodes are set at the connection of each component in the one-dimensional model to obtain pressure information. The flow source is coupled with the coupling surface at the inlet of the pipeline, and the pressure source is coupled with the coupling surface at the outlet of the pipeline. The external flow domain components consist of the underwater vehicle hull, inlet, and outlet. In the three-dimensional model, the sea outlet is extended by 1 m at both the outlet and the inlet, and the position 1 m extended from the sea outlet and the inlet is used as the coupling surface;

[0008] Set the flow field boundary conditions for one-dimensional-three-dimensional coupling calculation, construct a one-dimensional-three-dimensional coupling model of the gravity cooling system based on the data exchange in the coupling region, and perform one-dimensional-three-dimensional coupling flow field calculation;

[0009] Based on the fluid pulsation results obtained from the flow field calculation, perform the sound field calculation.

[0010] Among them, the construction of the one-dimensional model of the internal flow domain components of the gravity cooling system includes:

[0011] Construct a one-dimensional condenser model: The condenser is abstracted as consisting of a bundle of tubes connecting two water tanks with multiple bundles in the middle. Each water tank can be set to have a variable cross-sectional area and different heights can be specified. The total pressure loss of the one-dimensional condenser model is composed of the sum of the inlet loss, outlet loss, and pipeline loss;

[0012] Construct a one-dimensional eccentric butterfly valve model: The one-dimensional eccentric butterfly valve model uses a component double eccentric butterfly valve, where the inlet is connected to a flow source and the outlet end is connected to a pressure source to ensure the continuous flow of the fluid. The total pressure loss equation of the eccentric butterfly valve in the one-dimensional model is:

[0013]

[0014] Among them, P1 is the pressure at the inlet of the pipeline, P2 is the pressure at the outlet of the pipeline, ρ is the fluid density, A is the inner diameter area, K is the loss coefficient, which is related to the valve type, pipe diameter, valve opening, and Reynolds number, is the mass flow rate at the outlet;

[0015] Construct a one-dimensional pipeline model: The one-dimensional pipeline model uses a straight pipe model with a circular cross-section for the component, where the inlet is connected to a flow source and the outlet end is connected to a pressure source to ensure the continuous flow of the fluid. The total pressure loss equation of the pipeline in the one-dimensional model is:

[0016]

[0017] Among them, P1 is the pressure at the inlet of the pipeline, P2 is the pressure at the outlet of the pipeline, f is the friction coefficient, L is the pipeline length, ρ is the fluid density, A is the inner diameter area, is the mass flow rate at the inlet of the pipeline.

[0018] Among them, the construction of the three-dimensional model of the internal flow domain components of the gravity cooling system includes,

[0019] Construct a 3D model of the inlet of the gravity cooling system: The inlet parameters include the outlet diameter Φ of the inlet pipe, the length L1 of the inlet pipe section, the horizontal distance L2 from the end point of the arc section of the inlet pipe center line to the center of the inlet section, the arc radius R of the inlet pipe center line, the inlet height H of the inlet pipe, the width-to-height ratio B1 / H of the inlet, the total length LT of the inlet pipe fairing, the distance δ between the end of the inlet of the inlet pipe and the wall of the main model, the angle ɑ between the arc part of the center line and the horizontal line, and the bevel angle β of the fairing;

[0020] Construct a 3D model of the outlet of the gravity cooling system: The outlet parameters include the inlet diameter Φ of the outlet pipe, the cross-sectional diameter Φ1, the major axis Φ2 of the ellipse at the cut-off point of the gradually expanding part, the length L3 of the outlet pipe, the height B2 of the gradually expanding part, the distance C between the beveled part of the fairing and the main model, the chamfer γ of the outlet pipe fairing, and the angle ε between the underwater part of the side wall of the outlet pipe and the vertical plane.

[0021] Among them, the one-dimensional to three-dimensional coupling model of the gravity cooling system constructed based on the coupling region data exchange includes:

[0022] The data exchange includes an association process and an interpolation process. In constructing the one-dimensional to three-dimensional coupling model of the gravity cooling system, data is extracted from the one-dimensional model and applied to the grid of the three-dimensional model. At the coupling surface, a single integration point is paired with the surface grid, and flux interpolation and / or field interpolation are determined according to the type of data;

[0023] Based on the coupling algorithm, the coupling method, iteration method, relaxation factor, and convergence criterion are preset. Among them, the coupling method is weak bidirectional coupling, and the iterative coupling algorithm uses the.Gauss-Seidel algorithm;

[0024] The relaxation degree of data exchange is adjusted through the relaxation factor, and the formula is as follows:

[0025]

[0026] Among them, α is the relaxation factor, is the current iteration mapping value, which is the value mapped from the sender to the receiver grid, is the value received by the receiver in the previous iteration, is the new relaxation value, which is the updated value sent to the receiver and is obtained by weighted calculation of the current iteration mapping value and the value received in the previous iteration through the relaxation factor;

[0027] The difference is quantified based on the convergence criterion, and the formula is as follows:

[0028]

[0029] Among them, q n is the coupling quantity value at the nth time, q n+1is the coupling value of the (n + 1)th time, ||·|| ∞ is the infinity norm.

[0030] Among them, the flow field boundary conditions include

[0031] Turbulence model: Initially, the standard k-ε turbulence model is adopted, and after stabilization, it is switched to the LES large eddy model to capture more refined flow characteristics;

[0032] Numerical method: A segregated solver is used, and the turbulent kinetic energy, turbulent dissipation term, and momentum equation are all discretized using the second-order upwind scheme;

[0033] Solution algorithm: The SIMPLEC algorithm is used for pressure-velocity coupling calculation;

[0034] Boundary conditions: The fluid inlet boundary condition is set as a velocity inlet, the outlet boundary condition is set as a pressure outlet. In the one-dimensional to three-dimensional coupling, the pipe inlet coupling surface is set as a pressure outlet, and the pipe outlet coupling surface is set as a mass flow inlet. At the coupling surface, the mass flow rate and total pressure data are exchanged with the one-dimensional flow source and pressure source;

[0035] Wall treatment: The standard no-slip wall function is applied to the underwater vehicle hull and the pipe wall;

[0036] Symmetry boundary: The outer surface of the computational domain is set as a symmetry plane;

[0037] Fluid medium: Water;

[0038] Time step: 0.0004 s.

[0039] Among them, the underwater vehicle hull surface and the pipe are set as rigid walls. In the fluid domain, the main sound source domain is intercepted as a volume sound source. The sound propagation domain is the region between the sound source domain and the infinite element boundary, and its internal source term is zero. An acoustic model is constructed based on the sound source domain, the sound propagation domain, and the infinite boundary, including two acoustic models: the sound source domain without a pipe and the sound source domain with a pipe;

[0040] Select the maximum analysis frequency f max = 1000 Hz, the underwater sound speed c = 1500 m / s, and the minimum wavelength λ = c / f max = 1.5 m;

[0041] Set far-field and near-field acoustic monitoring points. The far-field acoustic monitoring points are composed of the measurement points on three orthogonal planes, corresponding to the x, y, and z axes respectively. With the center coordinate of the model as the center of the circle, 72 measurement points are arranged on each plane, totaling 216 measurement points. And main measurement points are set at five key positions of the far-field measurement points. The near-field acoustic monitoring points are set at the pipe inlet and outlet;

[0042] Based on the working condition of a ship speed of 12 kn, the flow characteristics and acoustic field characteristics of the gravity cooling system are analyzed to obtain the resistance loss coefficients of each component in the gravity cooling system model. And based on the analysis frequency range of 20 - 1000 Hz, through converting the sound pressure level SPL at each measurement point ii into the corresponding sound energy value, accumulating them and then averaging to obtain the average sound energy value, and obtaining the average total sound pressure level at multiple measurement points through SPL 总 = 10 × log 10 (average sound energy value), and calculating the far - field average total sound source level result of the gravity cooling system.

[0043] Among them, the standard k - ε model contains two transport equations: the turbulent kinetic energy k equation and the turbulent dissipation rate ε equation. The transport equations of the standard k - ε model are:

[0044]

[0045] Among them, G k and G b are turbulent kinetic energy terms. G k is caused by the average velocity gradient, and G b is caused by buoyancy; Y M is the influence of compressible turbulent pulsation expansion on the total dissipation rate; C 1ε , C 2ε , C 3ε are empirical values, and the default values are taken as C 1ε = 1.44, C 2ε = 1.92, C 3ε = 0.09; σ k , σ ε are the Prandtl numbers corresponding to the k equation and the ε equation respectively, and the default values are taken as σ k = 1.0, σ ε = 1.3; S k and S ε are user - defined terms; Pr t is the turbulent Prandtl number, and the default value is taken as Pr t = 0.85; g i is the component of gravitational acceleration; β is the thermal expansion coefficient; M t is the turbulent Mach number; a is the speed of sound.

[0046] Among them, the continuity equation and the momentum equation in the LES model can be expressed as:

[0047]

[0048] Among them, u i represents the velocity component associated with x i related, is the filtered average flow velocity component, ρ is the fluid density, is the sub-grid stress that describes the action of small-scale vortices on large-scale vortices;

[0049] According to the Boussinesq eddy viscosity hypothesis, it can also be expressed as:

[0050]

[0051] where, μ t is the turbulent viscosity; τ kk represents the isotropic part of the sub-grid stress; δ ij is the Dirac function; S ij represents the tensor of the Reynolds scale strain, and can be expressed as:

[0052]

[0053] The turbulent viscosity is solved by using the sub-grid stress model WALE model, and its calculation formula for the turbulent viscosity μt is as follows:

[0054]

[0055] where, the turbulent length scale L s and are defined as follows:

[0056] L s = min(κd, C w V 1 / 3 )

[0057]

[0058] where, κ is the non-Karman constant; d is the distance to the adjacent wall; C w is the WALE constant, with a value of 0.325; V 1 / 3 is the grid length scale.

[0059] The present invention establishes the original model of the gravity cooling system, conducts three-dimensional modeling on the inlet, outlet and outer flow field, conducts one-dimensional modeling on the in-flow field components such as condensers and butterfly valves, and studies the flow field characteristics and acoustic field characteristics of the gravity cooling system model based on the one-dimensional-three-dimensional coupling calculation method, which not only provides a new method for the flow noise prediction of the gravity cooling system, but also saves computing resources and computing time. Description of the Drawings

[0060] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present disclosure will become readily understandable. In the drawings, several embodiments of the present disclosure are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0061] Figure 1 is a flowchart showing a method for analyzing the flow noise at the inlet and outlet of a gravity cooling system according to an embodiment of the present invention;

[0062] Figure 2 is a schematic diagram of the flow of the gravity cooling system;

[0063] Figure 3 is a schematic diagram of a one-dimensional model of the internal flow domain of the gravity cooling system;

[0064] Figure 4 is a schematic diagram of a three-dimensional model of the external flow domain;

[0065] Figure 5 is a schematic diagram of the one-dimensional - three-dimensional coupled flow field model of the gravity cooling system and the setting of boundary conditions;

[0066] Figure 6 is a schematic diagram of the one-dimensional - three-dimensional coupled grid association;

[0067] Figure 7 is a cloud chart of acoustic radiation at different frequencies of the gravity cooling system. Detailed Embodiments

[0068] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0069] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. "Plural" generally includes at least two.

[0070] It should be understood that although the terms first, second, third, etc. may be used in the embodiments of the present invention to describe..., these... should not be limited to these terms. These terms are only used to distinguish.... For example, without departing from the scope of the embodiments of the present invention, the first... may also be referred to as the second..., and similarly, the second... may also be referred to as the first....

[0071] It should be understood that the term "and / or" used herein is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the character " / " in this text generally indicates that the associated objects before and after are in an "or" relationship.

[0072] Depending on the context, the words "if", "when" as used herein can be interpreted as "when...", "while...", "in response to determining", or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (stated condition or event)" can be interpreted as "when determined", "in response to determining", "when detecting (stated condition or event)", or "in response to detecting (stated condition or event)".

[0073] It should also be noted that the term "comprising", "including", or any other variant thereof is intended to cover non-exclusive inclusion, such that a commodity or device comprising a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such commodity or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the commodity or device comprising the said element.

[0074] The noise of the gravity cooling system is an important noise source of the flow noise of an underwater vehicle. As a whole, the internal and external flow fields of the gravity cooling system have the gravity flow characteristic, that is, the flow of the external flow field of the fluid drives the flow of the internal flow field, and the interaction between the internal and external flow fields forms a driving effect, which directly affects the change of the pressure of the flow rate in the system.

[0075] It is very important to comprehensively understand the generation, propagation process, and radiation characteristics at the inlet and outlet of the flow noise in the sea-connected pipeline of the gravity cooling system. For simulation research, considering the characteristics of the large scale and complex model of the gravity cooling system, a method is needed to reduce the computational amount and simulation time.

[0076] As Figure 1 shown, the present invention discloses a method for analyzing the flow noise at the inlet and outlet of a gravity cooling system, and the method includes:

[0077] Determine the composition structure of the gravity cooling system of the underwater vehicle, including the underwater vehicle hull, inlet, outlet, eccentric butterfly valve, condenser, and connecting pipe.

[0078] As a kind of sea-connected pipeline, the gravity cooling system generally consists of inlet / outlet, valve / pump components, condenser, grille, fairing and other parts. Its working principle is to utilize the dynamic head generated by the relative movement between the vehicle and seawater during navigation to increase the water pressure at the pipeline inlet, reduce the water pressure at the pipeline outlet, and push the cooling water to flow through the system and through the main condenser, effectively realizing the circulation of the cooling water. The flow schematic diagram of the gravity cooling system is as shown in Figure 2 shown.

[0079] The flow noise of the gravity cooling system mainly comes from the noise generated by the unstable flow of the fluid passing through components such as pumps and valves, as well as the fluid entering and discharging from the pipeline of the gravity cooling system.

[0080] Construct a one-dimensional model of the inner domain components and a three-dimensional model of the outer domain components of the gravity cooling system. Among them, the inner domain components are composed of an eccentric butterfly valve, a condenser and a connecting pipe. Nodes are set at the connection of each component in the one-dimensional model to obtain pressure information. The flow source is coupled with the coupling surface at the pipeline inlet, and the pressure source is coupled with the coupling surface at the pipeline outlet. The outer domain components are composed of an underwater vehicle hull, an inlet and an outlet. In the three-dimensional model, the outlet and inlet of the sea connection are extended by 1m at the same time, and the position 1m away from the extended outlet and inlet of the sea connection is used as the coupling surface.

[0081] The original model of the gravity cooling system consists of an inlet (including fairing), an outlet, an eccentric butterfly valve, a condenser, an axial flow pump and a connecting pipe connected together. The one-dimensional original model of the gravity cooling system is as shown in Figure 3 shown, with eccentric butterfly valves 1 and 2 in series, and eccentric butterfly valves 3 and 4 in series.

[0082] In a certain embodiment, constructing the one-dimensional model of the inner domain components of the gravity cooling system includes:

[0083] Constructing a one-dimensional condenser model: The condenser is abstracted as a bundle of tubes connecting two water tanks with multiple bundles connected in the middle. Each water tank can be set to have a variable cross-sectional area and can be specified with different heights. The total pressure loss of the one-dimensional condenser model is composed of the sum of the inlet loss, the outlet loss and the pipeline loss;

[0084] Constructing a one-dimensional eccentric butterfly valve model: The one-dimensional eccentric butterfly valve model uses a component double eccentric butterfly valve, where the inlet is connected to a flow source and the outlet end is connected to a pressure source to ensure the continuous flow of the fluid. The total pressure loss equation of the eccentric butterfly valve in the one-dimensional model is:

[0085]

[0086] where P1 is the pressure at the pipeline inlet, P2 is the pressure at the pipeline outlet, ρ is the fluid density, A is the inner diameter area, K is the loss coefficient, which is related to the valve type, pipe diameter, valve opening and Reynolds number. is the mass flow rate at the outlet;

[0087] Construct a one-dimensional pipeline model: The one-dimensional pipeline model uses a straight pipe model with a circular cross-section for the components, where the inlet is connected to a flow source and the outlet end is connected to a pressure source to ensure continuous fluid flow. The total pressure loss equation for the pipeline in the one-dimensional model is:

[0088]

[0089] where P1 is the pressure at the pipeline inlet, P2 is the pressure at the pipeline outlet, f is the friction coefficient, L is the pipeline length, ρ is the fluid density, A is the inner diameter area, is the mass flow rate at the pipeline inlet.

[0090] The outer flow domain includes the pipeline inlet (flow guide cover) and the pipeline outlet. Perform 3D modeling on the outer flow domain. To ensure the uniformity and stability of the flow rate at the coupling surface, take the positions 1m extended from the outlet and the inlet as the coupling surface, as Figure 4 shown.

[0091] In a certain embodiment, constructing the three-dimensional model of the inner flow domain components of the gravity cooling system includes,

[0092] Construct the three-dimensional model of the gravity cooling system inlet: The inlet parameters include the outlet diameter Φ of the inlet nozzle, the length L1 of the inlet nozzle section, the horizontal distance L2 from the end point of the arc section of the inlet nozzle center line to the center of the inlet section, the arc radius R of the inlet nozzle center line, the inlet height H of the inlet nozzle, the width-to-height ratio B1 / H of the inlet, the total length LT of the inlet nozzle flow guide cover, the distance δ between the end of the inlet nozzle and the wall surface of the main model, the angle ɑ between the arc part of the center line and the horizontal line, and the bevel angle β of the flow guide cover.

[0093] Construct the three-dimensional model of the gravity cooling system outlet: The outlet parameters include the inlet diameter Φ of the outlet nozzle, the cross-section diameter Φ1, the major axis Φ2 of the ellipse at the cut-off of the gradually expanding part, the length L3 of the outlet nozzle, the height B2 of the gradually expanding part, the distance C between the beveled part of the flow guide cover and the main model, the chamfer γ of the outlet nozzle flow guide cover, and the angle ε between the underwater part of the side wall of the outlet nozzle and the vertical plane.

[0094] Set the flow field boundary conditions for one-dimensional - three-dimensional coupling calculation, construct the one-dimensional - three-dimensional coupling model of the gravity cooling system based on the coupling region data exchange, and perform one-dimensional - three-dimensional coupling flow field calculation.

[0095] Before simulating the gravity cooling system, it is necessary to set the boundary conditions and initialize the parameters. Figure 5 Shows the flow field boundary conditions for one-dimensional - three-dimensional coupling calculation.

[0096] In a certain embodiment, the flow field boundary conditions include,

[0097] Turbulence model: Initially, the standard k-ε turbulence model is adopted, and after stabilization, it is switched to the LES large eddy model to capture finer flow characteristics;

[0098] Numerical method: A segregated solver is used, and the turbulent kinetic energy, turbulent dissipation term, and momentum equation are all discretized using the second-order upwind scheme;

[0099] Solution algorithm: The SIMPLEC algorithm is used for pressure-velocity coupling calculation;

[0100] Boundary conditions: The fluid inlet boundary condition is set as a velocity inlet, the outlet boundary condition is set as a pressure outlet. In the one-dimensional to three-dimensional coupling, the inlet coupling surface of the pipeline is set as a pressure outlet, and the outlet coupling surface of the pipeline is set as a mass flow inlet. At the coupling surface, mass flow rate and total pressure data are exchanged with the one-dimensional flow source and pressure source;

[0101] Wall treatment: The no-slip standard wall function is applied to the hull of the underwater vehicle and the pipeline wall;

[0102] Symmetry boundary: The outer surface of the computational domain is set as a symmetry plane;

[0103] Fluid medium: Water;

[0104] Time step: 0.0004 s.

[0105] In one embodiment, the standard k-ε includes two transport equations: the turbulent kinetic energy k equation and the turbulent dissipation rate ε equation. The transport equations of the standard k-ε model are:

[0106]

[0107] Where, G k and G b are the turbulent kinetic energy terms. G k is caused by the mean velocity gradient, and G b is caused by buoyancy; Y M is the effect of compressible turbulent pulsation expansion on the total dissipation rate; C 1ε 、C 2ε 、C 3ε are empirical values, and the default values are taken as C 1ε = 1.44, C 2ε = 1.92, C 3ε = 0.09; σ k 、σ ε are the Prandtl numbers corresponding to the k equation and the ε equation respectively, and the default values are taken as σ k = 1.0, σ ε = 1.3; S kand S ε is a custom item; Pr t is the turbulent Prandtl number, and the default value is Pr t = 0.85; g i is the component of gravitational acceleration; β is the coefficient of thermal expansion; M t is the turbulent Mach number; a is the speed of sound.

[0108] In one embodiment, the continuity equation and the kinetic equation in the LES model can be expressed as:

[0109]

[0110] where, u i represents the velocity component associated with x i ; is the filtered mean flow velocity component, ρ is the fluid density, is the subgrid-scale stress that describes the action of small-scale vortices on large-scale vortices;

[0111] According to the Boussinesq eddy viscosity hypothesis, it can also be expressed as:

[0112]

[0113] where, μ t is the turbulent viscosity; τ kk represents the isotropic part of the subgrid-scale stress; δ ij is the Dirac function; S ij represents the tensor of Reynolds-scale strain and can be expressed as:

[0114]

[0115] The turbulent viscosity is solved using the subgrid-scale stress model WALE model, and its turbulent viscosity μt calculation formula is as follows:

[0116]

[0117] where, the turbulent length scale L s and are defined as follows:

[0118] L s = min(κd, C w V 1 / 3 )

[0119]

[0120] where, κ is the non-Karman constant; d is the distance to the adjacent wall; C w is the WALE constant, with a value of 0.325; V1 / 3 is the grid length dimension.

[0121] One-dimensional to three-dimensional coupling is achieved through data exchange in the coupling region, and this process can be divided into two problems: how to transfer data and when to transfer data. The data exchange mechanism for one-dimensional to three-dimensional coupling is a key technology for realizing coupling between different dimensional models. This process requires extracting data from the simplified representation of the one-dimensional model and accurately applying it to the detailed grid of the three-dimensional model, and vice versa.

[0122] The data exchange process can be divided into two steps: association and interpolation. (1) Association. For each node or element of a grid, the goal of association is to determine the exact correspondence between each node or element in the sending grid and the corresponding position on the receiving grid. Data can then be exchanged between these associated nodes and / or elements. In one-dimensional to three-dimensional coupling, a single integration point is paired with the surface grid at the coupling surface. As Figure 6 shown. (2) Interpolation. Depending on the type of data, the interpolation process is divided into flux interpolation (such as mass flow) and field interpolation (such as pressure field). The transferred data must be adapted to the target grid. Flux interpolation adjusts the integration based on the cell size to ensure the physical consistency and accuracy of the data. Field interpolation involves using shape functions to interpolate field data to ensure accurate transfer of the data in terms of spatial distribution.

[0123] In one embodiment, a one-dimensional to three-dimensional coupling model of a gravity cooling system constructed based on data exchange in the coupling region includes:

[0124] The data exchange includes an association process and an interpolation process. In constructing the one-dimensional to three-dimensional coupling model of the gravity cooling system, data is extracted from the one-dimensional model and applied to the grid of the three-dimensional model. A single integration point is paired with the surface grid at the coupling surface, and flux interpolation and / or field interpolation are determined according to the type of data;

[0125] Based on the coupling algorithm, the coupling method, iteration method, relaxation factor, and convergence criterion are preset, where the coupling method includes weak bidirectional coupling, and the iterative coupling algorithm uses the.Gauss-Seidel algorithm;

[0126] The relaxation degree of data exchange is adjusted by the relaxation factor, and the formula is as follows:

[0127]

[0128] where α is the relaxation factor, is the current iteration mapping value, which is the value mapped from the sender to the receiver grid, is the value received by the receiver in the previous iteration, is the new relaxation value, which is the updated value sent to the receiver and is obtained by weighted calculation of the current iteration mapping value and the value received last time through the relaxation factor;

[0129] Quantify the difference based on the convergence criterion, and the formula is as follows:

[0130]

[0131] where q n is the coupling quantity value at the nth time, and q n+1 is the coupling quantity value at the (n + 1)th time, and ||·|| ∞ is the infinity norm.

[0132] Perform acoustic field calculation based on the fluid pulsation results obtained from the flow field calculation.

[0133] In a certain embodiment, the surface of the underwater vehicle shell and the pipeline are set as rigid wall surfaces. The main sound source domain is intercepted as a volume sound source in the fluid domain, and the sound propagation domain is the area between the sound source domain and the infinite element boundary, and its internal source term is zero. An acoustic model is constructed based on the sound source domain, the sound propagation domain, and the infinite boundary;

[0134] Select the maximum analysis frequency f max = 1000 Hz, the underwater sound speed c = 1500 m / s, and the minimum wavelength λ = c / f max = 1.5 m;

[0135] Set far-field and near-field acoustic monitoring points. The far-field acoustic monitoring points are composed of the measuring points on three orthogonal planes, corresponding to the x, y, and z axes respectively. With the center coordinate of the model as the center of the circle, 72 measuring points are arranged on each plane, totaling 216 measuring points, and main measuring points are set at five key positions of the far-field measuring points. The near-field acoustic monitoring points are set at the inlet and outlet of the pipeline;

[0136] Based on the working condition of a ship speed of 12 kn, analyze the flow characteristics and acoustic field characteristics of the gravity cooling system, obtain the resistance loss coefficients of each component in the gravity cooling system model, and based on the analysis frequency of 20 - 1000 Hz, through Convert the sound pressure level SPL ii of each measuring point into the corresponding sound energy value, accumulate and then average to obtain the average sound energy value, and obtain the average total sound pressure level of multiple measuring points through SPL 总 = 10 × log 10 (average sound energy value), and calculate the far-field average total sound source level result of the gravity cooling system.

[0137] The sound radiation nephogram of the gravity cooling system at different frequencies is as Figure 7 shown.

[0138] By establishing the original model of the gravity cooling system, three-dimensional modeling is carried out for the inlet, outlet and outer flow domain, one-dimensional modeling is carried out for the in-flow domain components such as condensers and butterfly valves, and based on the one-dimensional-three-dimensional coupling calculation method, the flow field characteristics and acoustic field characteristics of the gravity cooling system model are studied, which not only provides a new method for the flow noise prediction of the gravity cooling system, but also saves computing resources and computing time.

[0139] It should be noted that the computer-readable medium described above can be a computer-readable signal medium or a computer-readable storage medium or any combination of the two. A computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections with one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the above. In the present disclosure, a computer-readable storage medium can be any tangible medium that contains or stores a program, and this program can be used by or in combination with an instruction execution system, apparatus, or device. In the present disclosure, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, in which the computer-readable program code is carried. Such a propagated data signal can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. A computer-readable signal medium can also be any computer-readable medium other than a computer-readable storage medium, and this computer-readable signal medium can send, propagate, or transmit a program for use by or in combination with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted by any suitable medium, including but not limited to: wires, optical cables, RF (radio frequency), etc., or any suitable combination of the above.

[0140] The above computer-readable medium can be included in the above electronic device; or it can exist separately without being assembled into the electronic device.

[0141] Computer program code for performing the operations of this disclosure may be written in one or more programming languages or combinations thereof. The above-mentioned programming languages include object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, executed as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or it may be connected to an external computer (e.g., by connecting through the Internet using an Internet service provider).

[0142] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code that contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, may be implemented by a dedicated hardware-based system for performing the specified functions or operations, or may be implemented by a combination of dedicated hardware and computer instructions.

[0143] The units involved in the embodiments described in this disclosure may be implemented in software or in hardware. Among them, the name of the unit does not constitute a limitation to the unit itself in some cases.

[0144] The above describes the preferred embodiments of the present invention, aiming to make the spirit of the present invention clearer and easier to understand, and is not intended to limit the present invention. Any modifications, substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope defined by the appended claims of the present invention.

Claims

1. A method for analyzing the flow noise at the inlet and outlet of a gravity cooling system, comprising: Determining the composition structure of the gravity cooling system of an underwater vehicle, including the underwater vehicle hull, inlet, outlet, eccentric butterfly valve, condenser, and connecting pipe; Constructing a one-dimensional model of the inner domain components and a three-dimensional model of the outer domain components of the gravity cooling system. Among them, the inner domain components are connected by an eccentric butterfly valve, a condenser, and a connecting pipe. Nodes are set at the connection of each component in the one-dimensional model to obtain pressure information. The flow source is coupled with the coupling surface at the pipe inlet, and the pressure source is coupled with the coupling surface at the pipe outlet. The outer domain components consist of the underwater vehicle hull, inlet, and outlet. In the three-dimensional model, the outlet and inlet of the open sea outlet are extended by 1 m, and the position 1 m away from the extended outlet and inlet of the open sea outlet is used as the coupling surface; Setting the flow field boundary conditions for one-dimensional-three-dimensional coupling calculation, constructing a one-dimensional-three-dimensional coupling model of the gravity cooling system based on the coupling region data exchange, and performing one-dimensional-three-dimensional coupling flow field calculation; Performing sound field calculation based on the fluid pulsation results obtained from the flow field calculation; Constructing a one-dimensional model of the inner domain components of the gravity cooling system includes: Constructing a one-dimensional condenser model: The condenser is abstracted as a bundle of tubes connecting two water tanks with multiple bundles in the middle. Each water tank is set to have a variable cross-sectional area and a specified different height. The total pressure loss of the one-dimensional condenser model is composed of the sum of the inlet loss, outlet loss, and pipe loss; Constructing a one-dimensional eccentric butterfly valve model: The one-dimensional eccentric butterfly valve model uses a component double eccentric butterfly valve, where the inlet is connected to a flow source and the outlet end is connected to a pressure source to ensure the continuous flow of fluid. The total pressure loss equation of the eccentric butterfly valve in the one-dimensional model is: Wherein, P1 is the pressure at the pipe inlet, P2 is the pressure at the pipe outlet, ρ is the fluid density, A is the inner diameter area, and K is the loss coefficient, which is related to the valve type, pipe diameter, valve opening, and Reynolds number. is the mass flow rate at the outlet; Constructing a one-dimensional pipe model: The one-dimensional pipe model uses a straight pipe model with a circular cross-section as the component. The inlet is connected to a flow source and the outlet end is connected to a pressure source to ensure the continuous flow of fluid. The total pressure loss equation of the pipe in the one-dimensional model is: Wherein, P1 is the pressure at the pipe inlet, P2 is the pressure at the pipe outlet, f is the friction coefficient, L is the pipe length, ρ is the fluid density, A is the inner diameter area, and is the mass flow rate at the pipe inlet; Constructing a three-dimensional model of the inner domain components of the gravity cooling system includes Constructing a three-dimensional model of the inlet of the gravity cooling system: The inlet parameters include the outlet diameter Φ of the inlet connecting pipe, the length L1 of the inlet connecting pipe section, the horizontal distance L2 from the tangent line drawn from the end point of the arc section of the inlet connecting pipe center line to the center of the inlet section, the arc radius R of the inlet connecting pipe center line, the inlet height H of the inlet connecting pipe, the width-to-height ratio B1 / H of the inlet, the total length LT of the inlet connecting pipe fairing, the distance δ between the end of the inlet connecting pipe and the wall surface of the main model, the angle ɑ between the arc part of the center line and the horizontal line, and the bevel angle β of the fairing; Constructing a three-dimensional model of the outlet of the gravity cooling system: The outlet parameters include the inlet diameter Φ of the outlet connecting pipe, the cross-sectional diameter Φ1, the major axis Φ2 of the ellipse at the cut-off point of the gradually expanding part, the length L3 of the outlet connecting pipe, the height B2 of the gradually expanding part, the distance C between the beveled part of the fairing and the main model, the chamfer γ of the outlet connecting pipe fairing, and the angle ε between the underwater part of the side wall of the outlet connecting pipe and the vertical plane.

2. The method for analyzing the flow noise at the inlet and outlet of a gravity cooling system according to claim 1, characterized in that, Constructing a one-dimensional-three-dimensional coupling model of the gravity cooling system based on the coupling region data exchange includes: The data exchange includes an association process and an interpolation process. In constructing a one-dimensional to three-dimensional coupled model of a gravity cooling system, data is extracted from the one-dimensional model and applied to the grids of the three-dimensional model. At the coupling surface, a pairing method of a single integration point and surface grids is adopted, and flux interpolation and / or field interpolation are determined according to the type of data. Based on the coupling algorithm, the coupling method, iteration method, relaxation factor, and convergence criterion are preset. Among them, the coupling method is weak bi-directional coupling, and the iterative coupling algorithm adopts the Gauss-Seidel algorithm. The relaxation degree of data exchange is adjusted through the relaxation factor, and the formula is as follows: where α is the relaxation factor, is the current iteration mapping value, which is the value mapped from the sender to the receiver grid, is the value received by the receiver in the previous iteration, is the new relaxation value, which is the updated value sent to the receiver and is obtained by weighted calculation of the current iteration mapping value and the value received in the previous iteration through the relaxation factor; The difference is quantified based on the convergence criterion, and the formula is as follows: where q n is the coupling value at the nth time, q n+1 is the coupling value at the (n + 1)th time, and ||·|| ∞ is the infinity norm.

3. The method for analyzing the flow noise at the inlet and outlet of a gravity cooling system according to claim 1, characterized in that The flow field boundary conditions include Turbulence model: Initially, the standard k-ε turbulence model is adopted, and after stabilization, it is switched to the LES large eddy model to capture finer flow characteristics. Numerical method: A segregated solver is used, and the turbulent kinetic energy, turbulent dissipation term, and momentum equation are all discretized using the second-order upwind scheme. Solution algorithm: The SIMPLEC algorithm is used for pressure-velocity coupling calculation. Boundary conditions: The fluid inlet boundary condition is set as a velocity inlet, the outlet boundary condition is set as a pressure outlet. In the one-dimensional to three-dimensional coupling, the pipe inlet coupling surface is set as a pressure outlet, and the pipe outlet coupling surface is set as a mass flow inlet. At the coupling surface, mass flow rate and total pressure data are exchanged with the one-dimensional flow source and pressure source. Wall treatment: The no-slip standard wall function is applied to the underwater vehicle hull and pipe walls. Symmetry boundary: The outer surface of the computational domain is set as a symmetry plane. Fluid medium: Water Time step: 0.0004 s 4. A method for analyzing the flow noise at the inlet and outlet of a gravity cooling system according to claim 1, characterized in that: The underwater vehicle hull surface and pipes are set as rigid walls. In the fluid domain, the main sound source domain is intercepted as a volume sound source. The sound propagation domain is the area between the sound source domain and the infinite element boundary, and its internal source term is zero. An acoustic model is constructed based on the sound source domain, sound propagation domain, and infinite boundary. Select the maximum analysis frequency f max = 1000 Hz, the underwater sound speed c = 1500 m / s, the minimum wavelength λ = c / f max = 1.5 m; Far-field and near-field acoustic monitoring points are set. The far-field acoustic monitoring points are composed of measuring points on three orthogonal planes, corresponding to the x, y, and z axes respectively. With the center coordinate of the model as the center of the circle, 72 measuring points are arranged on each plane, totaling 216 measuring points. And main measuring points are set at five key positions of the far-field measuring points. The near-field acoustic monitoring points are set at the pipe inlet and outlet. Based on the working condition of a ship speed of 12 kn, the flow characteristics and acoustic field characteristics of the gravity cooling system are analyzed to obtain the resistance loss coefficients of each component in the gravity cooling system model. And based on the analysis frequency of 20 - 1000 Hz, by converting the sound pressure level SPL of each measurement point ii into the corresponding sound energy value, after accumulation and then averaging to obtain the average sound energy value, through SPL 总 = 10 × The average total sound pressure level of multiple measuring points is obtained by log10, and the far-field average total sound source level result of the gravity cooling system is calculated.

5. A method for analyzing the flow noise at the inlet and outlet of a gravity cooling system according to claim 3, characterized in that: The standard k-ε includes two transport equations: the turbulent kinetic energy k equation and the turbulent dissipation rate ε equation. The transport equations of the standard k-ε model are: Among them, G k and G b are the turbulent kinetic energy terms. G k is caused by the mean velocity gradient, and G b is caused by buoyancy; Y M is the influence of compressible turbulent pulsation expansion on the total dissipation rate; C 1ε 、C 2ε 、C 3ε are empirical values, and the default values are taken as C 1ε = 1.44, C 2ε = 1.92, C 3ε = 0.09; σ k 、σ ε are the Prandtl numbers corresponding to the k equation and the ε equation respectively, and the default values are taken as σ k = 1.0, σ ε = 1.3; S k and S ε are user-defined terms; Pr t is the turbulent Prandtl number, and the default value is taken as Pr t = 0.85; g i is the component of gravitational acceleration; β is the thermal expansion coefficient; M t is the turbulent Mach number; a is the speed of sound.

6. A method for analyzing the flow noise at the inlet and outlet of a gravity cooling system according to claim 3, characterized in that: The continuity equation and kinetic equation in the LES model are expressed as: where u i represents the velocity component associated with x i , is the filtered mean flow velocity component, ρ is the fluid density, is the subgrid-scale stress that describes the action of small-scale vortices on large-scale vortices; According to the Boussinesq eddy viscosity hypothesis, It is expressed as: where, μ t is the turbulent viscosity; τ kk represents the isotropic part of the sub-grid stress; δ ij is the Dirac function; S ij represents the tensor of the Reynolds-scale strain, expressed as: The turbulent viscosity is solved using the subgrid stress model, the WALE model, and its turbulent viscosity μ t The calculation formula is as follows: Among them, the turbulent length scale L s and are defined as follows: L s = min(κd, C w V 1 / 3 ) where κ is the non-Karman constant; d is the distance to the adjacent wall; C w is the WALE constant, with a value of 0.325; V 1 / 3 is the grid length dimension.

7. An apparatus for analyzing the flow noise at the inlet and outlet of a gravity cooling system, comprising: At least one processor; and At least one memory including computer program code Among them, The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to perform the method according to any one of claims 1-6.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores one or more programs which, when executed by a processor, implement the method according to any one of claims 1-7.

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