A method for calculating and reducing noise of fluid-structure coupling of bent pipe

Abstract

The application discloses a kind of elbow fluid-structure acoustic coupling calculation and noise reduction method, belong to pipeline test technical field.The application constructs the three-dimensional physical model of elbow and establishes elbow fluid-structure coupling model, accurately reflects the dynamic correlation between the internal fluid flow characteristics of elbow and solid structure response, by solving fluid velocity field, pressure field and turbulent flow characteristics, can capture the flow field disturbance caused by inertia, centrifugal force and elbow geometric change in the process of flow, quantitatively describes the dynamic load variation law that fluid exerts on pipe wall, effectively improves the understanding of complex elbow flow field behavior, extracts wall surface pressure distribution data and generates fluid disturbance data, can accurately predict the noise source distribution characteristics generated by flow-induced vibration, overall, it breaks through the problem that traditional single-field modeling method is insufficient to describe actual working condition, greatly improves the physical reality and prediction accuracy of simulation, effectively avoids the high cost and low efficiency problem caused by traditional trial-and-error method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipeline testing, in particular to a bend fluid-structure-acoustic coupling calculation and noise reduction method. BACKGROUND

[0002] Due to the complex flow state of the fluid inside the bend, strong flow disturbance, turbulent flow separation and secondary flow phenomena are easily caused, which leads to the dynamic pulsating load exerted by the fluid on the pipe wall, and further causes pipe wall vibration and structure sound radiation, forming a significant flow noise problem. There is a complex fluid-structure-acoustic coupling effect among flow excitation, structure vibration and sound wave radiation in the bend structure, making it particularly difficult to identify noise sources, predict sound pressure and optimize noise reduction.

[0003] In the prior art, the research on the fluid-structure-acoustic coupling problem in the bend is difficult to accurately reflect the complex interaction relationship of flow disturbance, structure response and sound field distribution under actual operating conditions. At the same time, the traditional noise prediction method often ignores the influence of the fluid disturbance source term on the evolution of the sound field, and cannot realize the accurate quantitative description of the noise source distribution and propagation path in the bend structure. SUMMARY

[0004] The purpose of the present application is to provide a bend fluid-structure-acoustic coupling calculation and noise reduction method to solve the problems raised in the background art.

[0005] To achieve the above purpose, the present application provides the following technical scheme: a bend fluid-structure-acoustic coupling calculation and noise reduction method, comprising:

[0006] A three-dimensional physical model of the bend is constructed and a bend fluid-structure coupling model is established, the velocity field, pressure field and turbulent flow characteristics of the fluid inside the bend are solved, the wall surface pressure distribution data is extracted, the dynamic load exerted by the fluid on the pipe wall during the flow process is quantitatively described, and the fluid disturbance data is generated;

[0007] A mathematical model of sound wave propagation inside the bend is established and an acoustic propagation model for different frequency band sound wave propagation characteristics is generated, and sound pressure distribution data is generated;

[0008] The fluid-structure-acoustic interaction is simulated by numerical simulation to generate wall vibration data;

[0009] A noise source spatial distribution model and a noise propagation path model are established, the noise source is quantitatively evaluated, and the noise level variation law and trend of the bend under typical operating conditions are predicted, the structural parameters of the bend are adjusted, the material layout is optimized, and the best structure combination is determined through repeated iterative simulation.

[0010] Further, the bend fluid-structure coupling model is established, which specifically further comprises:

[0011] determine the geometric parameters of the elbow according to the requirements of the target application, the geometric parameters including the bending radius, the pipe diameter size, the centerline length of the elbow, the wall thickness size, and the bending angle;

[0012] determine the physical property parameters of the fluid, the physical property parameters including the density, the viscosity, and the Reynolds number range, and determine the material characteristic parameters of the solid constituting the elbow, the material characteristic parameters including the elastic modulus, the Poisson's ratio, the density, the yield strength, and the internal damping characteristic of the material;

[0013] construct a three-dimensional physical model of the elbow through parameterized modeling based on the determined geometric parameters and material characteristic parameters, and distinguish the fluid region and the solid region in the modeling process, the fluid region being the internal cavity of the elbow and the solid region being the body of the pipe wall of the elbow;

[0014] set the inlet velocity boundary condition, the volume flow boundary condition, and the outlet static pressure boundary condition for the fluid region, and apply the no-slip boundary condition to the contact surface between the fluid and the solid; and set the fixed end, the simply supported, or the free boundary condition for the solid region according to the fixing mode and the working environment of the elbow;

[0015] initialize the fluid field variables including the initial velocity distribution, the initial pressure distribution, and the turbulence intensity distribution, and initialize the solid field variables including the initial displacement, the initial stress, and the initial strain;

[0016] establish the fluid-structure interaction model of the elbow according to the fluid control equation set and in combination with the solid control equation set, the fluid control equation set including the continuity equation, the momentum conservation equation, and the turbulence model equation, and the solid control equation set including the momentum conservation equation and the material constitutive relation.

[0017] Further, quantitatively describe the dynamic load exerted by the fluid on the pipe wall during the flow process, which further includes:

[0018] based on the fluid-structure interaction model of the elbow, numerically solve the velocity field and the pressure field of the fluid inside the elbow through the flow control equation set, obtain the velocity distribution, the pressure distribution, and the flow direction change trend of the fluid along the path of the elbow through steady-state solving, and obtain the pressure field data;

[0019] based on the pressure field data, extract the local pressure distribution characteristics of the inner wall surface of the elbow, and identify the high-pressure area, the low-pressure area, and the area with a sharp change in pressure gradient;

[0020] calculate the total pressure change trend of the fluid exerted on the wall surface through the tangential integral and the normal integral method, quantitatively describe the dynamic load characteristics exerted by the fluid on the pipe wall during the flow process, and establish a mathematical relationship model of the change of the wall surface pressure with the change of the flow position;

[0021] The velocity field and the pressure field are combined with the results of the numerical solution to identify different flow characteristic regions in the elbow pipe, including a main flow region, a separation region, a backflow region and a reattachment region.

[0022] The turbulent flow energy, the turbulent dissipation rate and the turbulent intensity distribution are calculated based on the turbulent flow model, and the fluid disturbance data are generated in combination with the pressure field data.

[0023] Further, a description model for the sound wave propagation characteristics of different frequency bands is generated, and specifically further includes:

[0024] The flow field disturbance information is extracted, including fluid velocity disturbance, pressure disturbance and turbulent flow energy change data.

[0025] The flow field disturbance information is converted into an acoustic source term and an acoustic propagation model is constructed, the acoustic source term includes a mass source term, a momentum source term and an energy source term, a mathematical expression of the flow-induced sound source term is established as an input condition of the acoustic control equation set, the acoustic control equation set includes a sound wave equation, a pressure disturbance equation and a potential flow equation.

[0026] The control equation describing the small-amplitude disturbance sound wave propagation is established, and the control equation includes a mass conservation equation, a momentum conservation equation and an energy conservation equation; in the three-dimensional physical model of the elbow pipe, the acoustic control equation is discretely processed and the sound field is numerically solved.

[0027] Further, a description model for the sound wave propagation characteristics of different frequency bands is generated, and specifically further includes:

[0028] In the numerical solution process, reasonable boundary conditions are set, including an acoustic hard boundary condition for the solid surface of the elbow pipe, a free radiation boundary or an acoustic absorption boundary is set at the outlet end of the elbow pipe, and the sound pressure distribution diagram, the sound pressure level change curve and the sound energy spectrum density distribution diagram at different positions in the elbow pipe are obtained.

[0029] The sound pressure distribution characteristics of different regions of the elbow pipe are extracted, and the sound pressure peak value region, the sound pressure node region and the sound energy concentration region are identified.

[0030] The energy loss of the sound wave when propagating between the curved section and the straight pipe section is obtained, and the sound energy density distribution is combined to draw a sound wave energy flow path diagram, and the energy convergence region and the energy dissipation region are identified.

[0031] Further, the fluid-structure-sound interaction is simulated by numerical simulation, and specifically further includes:

[0032] Based on the fluid-structure coupling model of the elbow and the acoustic propagation model, a multi-physical field joint simulation calculation model is constructed, which simultaneously couples the fluid dynamics equation, the solid dynamics equation and the acoustic control equation; the fluid velocity field, the pressure field change, the solid displacement field, the stress field distribution and the sound pressure field distribution data at different time steps are output, and the sound pressure time history data in the joint simulation process are recorded;

[0033] The sound pressure time history data is subjected to fast Fourier transform processing to obtain a frequency domain sound pressure level spectrum;

[0034] Based on the sound pressure level spectrum, the main noise frequency components and the dominant frequency band are identified, the peak frequency, the primary and secondary frequency distribution and the energy concentration frequency band are extracted; the contribution proportion of different regions in the elbow structure to the overall sound radiation is combined with the sound source positioning to determine the main sound source position, and noise source distribution data is generated;

[0035] The sound source intensity distribution map, the dominant frequency change curve and the sound source contribution rate analysis table are output;

[0036] Based on modal analysis, the local resonance region and the sound wave amplification effect region of the structure are identified.

[0037] Further, based on modal analysis, the local resonance region and the sound wave amplification effect region of the structure are identified, which specifically further includes:

[0038] Through modal analysis, the natural frequency, mode shape and vibration energy distribution characteristics of the elbow structure are extracted, the regions prone to local resonance of the elbow wall under fluid disturbance excitation are identified, and the corresponding resonance frequency and amplitude are quantitatively given;

[0039] Combined with acoustic modal analysis, the standing wave zone and amplification zone of sound waves formed under specific structural forms in the elbow are identified, and the contribution of sound wave standing effect to the overall sound pressure level gain is quantitatively described;

[0040] Local resonance mode distribution map, sound standing wave mode diagram and sound energy gain distribution curve are generated.

[0041] Further, the noise sources are quantitatively evaluated and the noise level variation law and trend of the elbow under typical operating conditions are predicted, which specifically further includes:

[0042] Based on the fluid disturbance data, the wall vibration data and the sound pressure distribution data, the sound source intensity distribution of the elbow inside and around the space is extracted, the main noise source region, the secondary noise source region and the noise hot spot region are identified, and the contribution rate of each noise source is quantified;

[0043] Based on the sound energy flow path tracking method, the noise energy propagation path diagram is drawn, the propagation trajectory, energy attenuation law and directivity change of sound wave after being emitted from the source in the internal and external space of the elbow pipe are qualitatively and quantitatively described, and the noise source spatial distribution model and the noise propagation path model of the elbow pipe structure are generated;

[0044] The sound power, sound pressure level and radiation directivity data of each dominant sound source in the noise source distribution data are extracted, the total sound power value of the elbow pipe outlet end and the surrounding specific measuring points is calculated, the main noise frequency component is obtained through frequency spectrum analysis, the sound pressure level curve with frequency change is drawn, the peak frequency and the main frequency band range with energy concentration are identified, the main noise radiation direction and the secondary radiation direction are identified, and the sound energy distribution characteristics in different directions are quantified;

[0045] The noise level change law and the acoustic hotspot area under different working conditions are predicted.

[0046] Further, the noise level change law and the acoustic hotspot area under different working conditions are predicted, and specifically further comprising:

[0047] Based on the simulation calculation results of multiple groups of typical working conditions, the noise power, sound pressure level and frequency spectrum change data corresponding to each working condition are extracted, and the typical working conditions are set by different flow rates, pressures and vibration characteristics;

[0048] The response curve of noise level with flow rate change and geometric structure parameter change is established, and the trend law of noise change with working condition is quantitatively described;

[0049] By comparing the sound source distribution characteristics and energy aggregation conditions under different working conditions, the acoustic hotspot area formed under each working condition is identified, and the acoustic hotspot area includes the sound energy aggregation area, the sound pressure peak area and the sound wave standing enhancement area;

[0050] The sound pressure distribution cloud map, the sound source position change map and the sound power change trend table under the typical working condition are output.

[0051] Further, the best structure combination is determined through repeated iteration simulation, and specifically further comprising:

[0052] Based on the noise source spatial distribution model and the noise propagation path model, the high noise area with the most concentrated noise energy and the strongest sound radiation in the elbow pipe and the high frequency excitation area prone to high frequency local vibration in the elbow pipe are identified;

[0053] For high noise area, the ratio of bending radius and diameter of the elbow pipe is optimized, the wall thickness distribution of the elbow is adjusted, and the local curvature change is optimized; a buffer zone is added in the high flow rate change area inside the elbow pipe, the pipe diameter is locally enlarged and a slow transition section is added, and a streamline guide structure is arranged at the inlet and outlet of the elbow; composite materials, damping materials or sandwich structures are used in the high frequency excitation area, and the material thickness and structure level are arranged according to different areas;

[0054] Iterative simulation is carried out, and the iterative simulation results of the overall flow stability of the elbow pipe, the turbulence intensity, the local sound pressure peak value change, the noise radiation level, the flow field uniformity, the turbulent kinetic energy, the turbulent dissipation rate, the wall vibration amplitude, the resonance frequency, the sound energy amplification effect and the high frequency noise level are obtained;

[0055] Based on the iterative simulation results, iterative simulation is repeatedly carried out until the best structure combination is determined.

[0056] Compared with the prior art, the beneficial effects of the present application are:

[0057] 1. The present application quantitatively describes the dynamic load exerted by the fluid on the pipe wall during the flow process, deeply reveals the details of the correlation between the flow field change and the wall stress, and uses the wall pressure distribution extraction, tangential and normal integral method, which can not only identify the instantaneous load change under the action of the fluid, but also establish the mathematical relationship between the pressure change and the path change of the elbow pipe, which is helpful to find the potential local stress concentration and fatigue risk point, and further strengthen the understanding of the fluid disturbance characteristics by combining the comprehensive analysis of the turbulent kinetic energy, the turbulent dissipation rate and the turbulent intensity distribution, which makes up for the limitations of traditional static load analysis under complex flow conditions.

[0058] 2. The present application can more accurately simulate the propagation behavior of sound waves in the complex geometric conditions inside the elbow pipe by generating a description model for the sound wave propagation characteristics of different frequency bands, and the control equation set for the small amplitude disturbance sound wave propagation characteristics makes the sound field numerical solution still maintain good calculation stability and physical consistency under the condition of high frequency and low amplitude change, and the output of sound pressure distribution diagram, sound pressure level change curve and sound energy spectrum density distribution diagram provides intuitive basis for energy distribution characteristic analysis of different frequency bands, which breaks through the problem that traditional acoustic simulation is difficult to accurately describe the local sound pressure peak value and energy concentration area, and provides strong support for subsequent noise control strategy making and structure acoustic optimization.

[0059] 3.The method can realize unified modeling and linkage analysis of the behavior of multiple physical fields in the elbow through numerical simulation of fluid-structure-acoustic interaction, synchronous coupling of fluid dynamics equations, solid dynamics equations and acoustic control equations, which not only improves the physical authenticity of the simulation, but also greatly enhances the prediction ability of flow-induced vibration and acoustic radiation phenomena, and the frequency domain sound pressure spectrum obtained makes the main noise components and frequency distribution clear at a glance, combined with sound source positioning and modal analysis, the local resonance region and sound amplification effect area of the structure can be accurately identified, and the weak links in the structure design can be effectively found.

[0060] 4.The method can comprehensively master the internal and external sound energy distribution state of the elbow by quantitatively evaluating the noise source and predicting the noise level change rule and trend of the elbow under typical operating conditions, and can effectively identify the noise generation mechanism and radiation characteristics under different flow conditions, and the establishment of the sound source spatial distribution model and the propagation path model makes the sound wave energy transmission rule and attenuation behavior more clear, and through extraction of the dominant sound source sound power and radiation directivity data, the main noise radiation direction and energy distribution characteristics can be quantitatively evaluated, which can effectively support the acoustic design optimization of the elbow structure and the formulation of noise control measures under the operating state, and improve the product quiet performance and environmental adaptability. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 It is a flow-structure-acoustic coupling calculation and noise reduction method flowchart of the elbow. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0063] Please refer to Figure 1 The present application provides the following technical solutions:

[0064] An elbow fluid-structure-acoustic coupling calculation and noise reduction method, comprising:

[0065] A three-dimensional physical model of the elbow is constructed, and an elbow fluid-structure coupling model is established, the velocity field, pressure field and turbulent flow characteristics of the fluid in the elbow are solved, the wall pressure distribution data is extracted, the dynamic load exerted by the fluid on the pipe wall during the flow process is quantitatively described, and the fluid disturbance data is generated;

[0066] A mathematical model of sound wave propagation in the elbow is established, and an acoustic propagation model for different frequency band sound wave propagation characteristics is generated, and sound pressure distribution data is generated;

[0067] The fluid-structure interaction is simulated by numerical simulation to generate the wall vibration data;

[0068] The noise source spatial distribution model and the noise propagation path model are established to quantitatively evaluate the noise source and predict the noise level variation law and trend of the elbow under the typical operating state, adjust the structural parameters of the elbow, optimize the material layout, and determine the optimal structure combination through repeated iteration simulation.

[0069] In the above embodiment, by constructing a three-dimensional physical model of the elbow and establishing a fluid-structure coupling model of the elbow, the dynamic correlation between the internal fluid flow characteristics of the elbow and the structure response of the solid is accurately reflected, the fluid velocity field, pressure field and turbulence characteristics are solved, the flow field disturbance caused by inertia, centrifugal force and geometric change of the elbow in the flow process is captured, and the dynamic load variation law of the fluid exerted on the pipe wall is quantitatively described, thereby effectively improving the understanding of the flow field behavior of the complex elbow. By extracting the wall pressure distribution data and generating the fluid disturbance data, the noise source distribution characteristics generated by the flow-induced vibration can be accurately predicted. Overall, the problem that the actual working condition is not fully described by the traditional single-field modeling method is broken through, and the physical authenticity and prediction accuracy of the simulation are greatly improved.

[0070] The fluid-structure coupling model of the elbow is established, and specifically further comprises:

[0071] According to the target application requirements, the geometric structure parameters of the elbow are determined, including the bending radius, the pipe diameter size, the center line length of the elbow, the wall thickness size and the bending angle;

[0072] The physical property parameters of the fluid are determined, including the density, the viscosity and the Reynolds number range, and the material characteristic parameters of the solid constituting the elbow are determined, including the elastic modulus, the Poisson's ratio, the density, the yield strength and the internal damping characteristics of the material;

[0073] Based on the determined geometric structure parameters and material characteristic parameters, a three-dimensional physical model of the elbow is constructed by parameterized modeling, and the fluid region and the solid region are distinguished in the modeling process. The fluid region is the internal cavity of the elbow, and the solid region is the pipe wall body of the elbow;

[0074] For the fluid region, the inlet velocity boundary condition, the volume flow boundary condition and the outlet static pressure boundary condition are set, and the no-slip boundary condition is applied to the contact surface between the fluid and the solid. For the solid region, the fixed end, the simply supported or free boundary condition is set according to the fixing mode and the working environment of the elbow;

[0075] The fluid field variables are initialized, including the initial velocity distribution, the initial pressure distribution and the turbulence intensity distribution, and the solid field variables are initialized, including the initial displacement, the initial stress and the initial strain;

[0076] According to the fluid control equation set and in combination with the solid control equation set, the bend fluid-structure coupling model is established, the fluid control equation set includes the continuity equation, the momentum conservation equation and the turbulent flow model equation, and the solid control equation set includes the momentum conservation equation and the material constitutive relation.

[0077] In the above embodiment, by refining the setting of the geometric structure parameters and the fluid and material attribute parameters when establishing the bend fluid-structure coupling model, the model parameterization and controllability are realized, especially in the aspects of the differentiated modeling of the fluid and solid regions, the accurate setting of the boundary conditions and the reasonable initialization of the initial variables, the stability and convergence of the subsequent numerical simulation are effectively ensured, the organic combination of the fluid continuity equation, the momentum conservation equation and the turbulent flow model makes the flow phenomenon modeling more in line with the actual working conditions, the synchronous introduction of the solid momentum equation and the material constitutive relation makes the structure response simulation have higher mechanical rationality, and the multi-parameter accurate definition and coupling control method significantly improves the comprehensiveness and prediction ability of the modeling.

[0078] The dynamic load exerted by the fluid on the pipe wall during the flow process is quantitatively described, and specifically includes:

[0079] Based on the bend fluid-structure coupling model, the velocity field and the pressure field of the fluid inside the bend are numerically solved through the flow control equation set, the velocity distribution, the pressure distribution and the flow direction change trend of the fluid along the bend path are obtained through steady-state solving, and the pressure field data are obtained;

[0080] Based on the pressure field data, the local pressure distribution characteristics of the inner wall surface of the bend are extracted, and the high-pressure area, the low-pressure area and the area with sharp pressure gradient change are identified;

[0081] The total pressure change trend exerted by the fluid on the wall is calculated through the tangential integral and the normal integral method, the dynamic load characteristics exerted by the fluid on the pipe wall during the flow process are quantitatively described, and a mathematical relationship model of the wall pressure change with the flow position change is established;

[0082] In combination with the results of the numerical solving of the velocity field and the pressure field, different flow characteristic regions inside the bend are identified, the flow characteristic regions include the main flow region, the separation region, the backflow region and the reattachment region.

[0083] Based on the turbulent flow model, the turbulent kinetic energy, the turbulent dissipation rate and the turbulent intensity distribution are calculated, and the fluid disturbance data are generated in combination with the pressure field data.

[0084] In the above embodiment, by quantitatively describing the dynamic load exerted by the fluid on the pipe wall during the flow process, the detailed correlation between the flow field change and the wall force can be revealed in depth. By using the wall pressure distribution extraction, tangential and normal integral method, not only the instantaneous load change under the action of the fluid can be identified, but also the mathematical relationship between the pressure change and the change of the bend pipe path can be established, which is helpful to find the potential local stress concentration and fatigue risk point. Combined with the comprehensive analysis of the turbulent kinetic energy, turbulent dissipation rate and turbulent intensity distribution, the mastery of the fluid disturbance characteristics is further strengthened, which effectively makes up for the limitations of traditional static load analysis under complex flow conditions, and provides high-precision input for subsequent noise source identification, local vibration analysis and structure optimization design.

[0085] A description model for the propagation characteristics of sound waves of different frequency bands is generated, and specifically further includes:

[0086] Extracting flow field disturbance information, the flow field disturbance information including fluid velocity disturbance, pressure disturbance, and turbulent kinetic energy change data;

[0087] Converting the flow field disturbance information into acoustic source terms and constructing an acoustic propagation model, the acoustic source terms including mass source terms, momentum source terms, and energy source terms, establishing a mathematical expression of the flow-induced acoustic source terms as input conditions of the acoustic control equations, the acoustic control equations including acoustic wave equations, pressure disturbance equations, and potential flow equations;

[0088] Establishing a control equation describing the propagation of small-amplitude sound waves, the control equation including mass conservation equations, momentum conservation equations, and energy conservation equations; in the three-dimensional physical model of the bend pipe, the acoustic control equations are discretely processed and the sound field is numerically solved;

[0089] In the numerical solving process, reasonable boundary conditions are set, the boundary conditions including the sound hard boundary condition of the solid surface of the bend pipe, the free radiation boundary or the sound absorption boundary set at the outlet end of the bend pipe, obtaining the sound pressure distribution diagram, the sound pressure level change curve, and the sound energy spectrum density distribution diagram at different positions inside the bend pipe;

[0090] Extracting the sound pressure distribution characteristics of different regions of the bend pipe, identifying the sound pressure peak value area, the sound pressure node area, and the sound energy aggregation area;

[0091] Obtaining the energy loss of sound waves when propagating between the curved section and the straight pipe section, combining the sound energy density distribution, drawing the sound wave energy flow path diagram, and identifying the energy convergence area and the energy dissipation area.

[0092] In the above embodiment, by generating a description model for the propagation characteristics of sound waves in different frequency bands, the propagation behavior of sound waves in the complex geometric conditions inside the elbow pipe can be simulated more accurately. The introduction of the acoustic source term and the establishment of the acoustic control equation make the flow-induced noise modeling more realistic and detailed. The control equation set for the small-amplitude sound wave propagation characteristics ensures that the numerical solution of the sound field remains stable and physically consistent under high-frequency and low-amplitude conditions. By reasonably setting the boundary conditions, the influence of sound wave reflection and standing wave on the calculation accuracy can be effectively avoided. The output of sound pressure distribution, sound pressure level change curve and sound energy spectrum density distribution provides an intuitive basis for energy distribution characteristic analysis in different frequency bands, and breaks through the problem that traditional acoustic simulation cannot accurately describe local sound pressure peak and energy concentration area, providing strong support for subsequent noise control strategy formulation and structural acoustic optimization.

[0093] The fluid-structure interaction is simulated by numerical simulation, which specifically includes:

[0094] Based on the fluid-structure coupling model and the acoustic propagation model, a multi-physical field joint simulation calculation model is constructed, and the joint simulation model is coupled with the fluid dynamics equation, the solid dynamics equation and the acoustic control equation; the fluid velocity field, the pressure field change, the solid displacement field, the stress field distribution and the sound pressure field distribution data at different time steps are output, and the sound pressure time history data in the joint simulation process are recorded;

[0095] The sound pressure time history data is processed by fast Fourier transform to obtain a frequency domain sound pressure level spectrum;

[0096] Based on the sound pressure level spectrum, the main noise frequency components and the dominant frequency band are identified, the peak frequency, the primary and secondary frequency distribution and the energy concentration frequency band are extracted, the contribution proportion of different regions in the elbow structure to the overall sound radiation is determined in combination with the sound source positioning, the main sound source position is determined, and the noise source distribution data are generated;

[0097] The sound source intensity distribution, the dominant frequency change curve and the sound source contribution rate analysis table are output;

[0098] Based on modal analysis, the local resonance region and the sound wave amplification effect region of the structure are identified;

[0099] Through modal analysis, the natural frequency, mode shape and vibration energy distribution characteristics of the elbow structure are extracted, the regions prone to local resonance of the elbow wall under fluid disturbance excitation are identified, and the corresponding resonance frequency and amplitude are quantitatively given;

[0100] In combination with acoustic modal analysis, the standing wave region and the amplification region of sound waves in the elbow pipe under specific structural forms are identified, and the contribution of sound wave standing effect to the overall sound pressure level gain is quantitatively described;

[0101] A local resonance mode distribution map, a sound standing wave mode map and a sound energy gain distribution curve are generated.

[0102] In the above embodiment, the fluid-structure-acoustic interaction is simulated by numerical simulation, the unified modeling and linkage analysis of the multi-physical field behavior in the elbow pipe can be realized, the synchronous coupling of the fluid dynamics equation, the solid dynamics equation and the acoustic control equation not only improves the physical authenticity of the simulation, but also greatly enhances the prediction ability of the flow-induced vibration and the acoustic radiation phenomenon. After the time history data of the sound pressure is processed by the Fourier transform, the frequency domain sound pressure spectrum obtained makes the main noise component and the frequency distribution clear at a glance. Combined with the sound source positioning and the modal analysis, the local resonance region of the structure and the sound wave amplification effect region can be accurately identified, and the weak links in the structure design can be effectively found. The comprehensive simulation strategy of multiple scales and multiple frequency bands significantly improves the accuracy of the noise source identification and the sound radiation path tracking.

[0103] The noise source is quantitatively evaluated, and the noise level variation law and trend of the elbow pipe under typical operating conditions are predicted, which specifically includes:

[0104] Based on the fluid disturbance data, the wall vibration data and the sound pressure distribution data, the sound source intensity distribution in the elbow pipe and the surrounding space is extracted, the main noise source region, the secondary noise source region and the noise hotspot region are identified, and the contribution rate of each noise source is quantified;

[0105] Based on the sound energy flow path tracking method, a noise energy propagation path diagram is drawn, the propagation trajectory, energy attenuation law and directivity change of the sound wave after being emitted from the source in the elbow pipe and the external space are qualitatively and quantitatively described, and a noise source spatial distribution model and a noise propagation path model of the elbow pipe structure are generated;

[0106] The sound power, sound pressure level and radiation directivity data of each dominant sound source in the noise source distribution data are extracted, the total sound power value of the elbow pipe outlet end and the surrounding specific measuring points is calculated, the main noise frequency component is obtained through spectrum analysis, the sound pressure level curve with frequency change is drawn, the peak frequency and the main frequency band range with energy concentration are identified; the main noise radiation direction and the secondary radiation direction are identified, and the sound energy distribution characteristics in different directions are quantified;

[0107] The noise level variation law and the acoustic hotspot region under different working conditions are predicted;

[0108] Based on the simulation calculation results under multiple typical working conditions, the noise power, sound pressure level and spectrum change data corresponding to each working condition are extracted, and the typical working conditions are parameterized by different flow rates, pressures and vibration characteristics;

[0109] The response curve of the noise level with the flow rate change and the geometric structure parameter change is established, and the trend law of the noise with the working condition change is quantitatively described;

[0110] By comparing the sound source distribution characteristics and energy aggregation under different working conditions, the acoustic hot spot area under each working condition is identified, including the sound energy aggregation area, the sound pressure peak area and the sound wave standing enhancement area;

[0111] Output the sound pressure distribution cloud map, sound source position change graph and sound power change trend table under typical working conditions.

[0112] In the above embodiment, by quantitatively evaluating the noise source and predicting the noise level change rule and trend of the elbow under typical operating state, not only the internal and external sound energy distribution state of the elbow can be comprehensively mastered, but also the noise generation mechanism and radiation characteristics under different flow conditions can be effectively identified. The establishment of the sound source spatial distribution model and the propagation path model makes the sound wave energy transmission rule and the attenuation behavior more clear. By extracting the dominant sound source sound power and radiation directivity data, the main noise radiation direction and energy distribution characteristics can be quantitatively evaluated, the sound pressure level change curve can be drawn, and the noise level under different flow rates, pressures and vibration conditions can be predicted. This noise change trend analysis based on multi-condition simulation can effectively support the acoustic design optimization of the elbow structure and the formulation of noise control measures under operating conditions, and improve the product quietness performance and environmental adaptability.

[0113] The optimal structure combination is determined through repeated iteration simulation, which further includes:

[0114] Based on the noise source spatial distribution model and the noise propagation path model, the high noise area with the most concentrated noise energy and the strongest sound radiation in the elbow, and the high frequency excitation area prone to high frequency local vibration in the elbow are identified;

[0115] For the high noise area, the ratio of the bending radius to the diameter of the elbow is optimized, the wall thickness distribution at the elbow is adjusted, and the local curvature change is optimized. A buffer zone is added in the high flow rate change area inside the elbow, the pipe diameter is locally enlarged and a slow transition section is added, and a flow line guiding structure is arranged at the inlet and outlet of the elbow. In the high frequency excitation area, composite materials, damping materials or sandwich structures are used, and the material thickness and structure level are arranged according to different areas;

[0116] The iteration simulation results of the overall flow stability of the elbow, the local sound pressure peak change, the noise radiation level, the flow field uniformity, the turbulent kinetic energy, the turbulent dissipation rate, the wall vibration amplitude, the resonance frequency, the sound energy amplification effect and the high frequency noise level are obtained through iteration simulation;

[0117] Based on the iteration simulation results, repeated iteration simulation is carried out until the optimal structure combination is determined.

[0118] In the above embodiment, the optimal structure combination is determined through repeated iterative simulation, the bending pipe flow characteristics, noise source distribution characteristics and acoustic response law can be systematically optimized, according to the simulation results, the bending pipe geometry and material layout are adjusted for high noise area and high frequency excitation area, the local vibration amplitude and sound energy amplification effect can be significantly reduced, the local optimization measures include adjusting the bending radius and diameter ratio, optimizing the wall thickness distribution, increasing the streamline guide structure and applying high damping composite material, the overall flow stability and acoustic performance of the bending pipe are effectively improved, through multiple iterative simulation, the optimal structure combination is gradually converged, the noise level is significantly reduced, the turbulence intensity is weakened, the wall vibration amplitude is reduced and the acoustic standing wave effect is inhibited, the simulation analysis results are used to guide the structure design optimization, the high cost and low efficiency problems caused by the traditional trial and error method are effectively avoided.

[0119] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art in the technical range disclosed by the present application, according to the technical scheme and the inventive concept of the present application, equivalent replacement or change, should be covered within the protection scope of the present application.

Claims

1. A method for fluid-structure acoustic coupling computation and noise reduction of a bent pipe, characterized in that, The method comprises the following steps: a three-dimensional physical model of the elbow pipe is constructed, and an elbow pipe fluid-structure coupling model is established, the velocity field, pressure field and turbulent flow characteristics of the fluid in the elbow pipe are solved, the wall surface pressure distribution data is extracted, the dynamic load exerted by the fluid on the pipe wall during the flow process is quantitatively described, and fluid disturbance data is generated; a mathematical model of sound wave propagation in the elbow pipe is established, and an acoustic propagation model for the sound wave propagation characteristics of different frequency bands is generated, and sound pressure distribution data is generated; the fluid-structure interaction is simulated by numerical simulation, and wall vibration data is generated; a noise source spatial distribution model and a noise propagation path model are established, the noise source is quantitatively evaluated, and the noise level variation law and trend of the elbow pipe under typical operating conditions are predicted, the structural parameters of the elbow pipe are adjusted, the material layout is optimized, and the optimal structure combination is determined through repeated iterative simulation; the dynamic load exerted by the fluid on the pipe wall during the flow process is quantitatively described, and the method further comprises the following steps: based on the elbow pipe fluid-structure coupling model, the velocity field and pressure field of the fluid in the elbow pipe are numerically solved by solving the flow control equation set, the velocity distribution, pressure distribution and flow direction change trend of the fluid along the elbow pipe path are obtained by steady-state solving, and pressure field data is obtained; based on the pressure field data, the local pressure distribution characteristics of the inner wall surface of the elbow pipe are extracted, and high-pressure areas, low-pressure areas and areas with large pressure gradient changes are identified; the total pressure change trend exerted by the fluid on the wall is calculated by tangential integration and normal integration method, the dynamic load characteristics of the fluid on the pipe wall during the flow process are quantitatively described, and a mathematical relationship model of the wall pressure change with the flow position change is established; combined with the results of the velocity field and pressure field numerical solving, different flow characteristic regions in the elbow pipe are identified, and the flow characteristic regions include a main flow region, a separation region, a backflow region and a reattachment region; based on the turbulent flow model, the turbulent kinetic energy, turbulent dissipation rate and turbulent intensity distribution are calculated, and the fluid disturbance data is generated in combination with the pressure field data; the noise source is quantitatively evaluated, and the noise level variation law and trend of the elbow pipe under typical operating conditions are predicted, and the method further comprises the following steps: based on the fluid disturbance data, wall vibration data and sound pressure distribution data, the sound source intensity distribution in the elbow pipe and the surrounding space is extracted, the main noise source region, secondary noise source region and noise hotspot region are identified, and the contribution rate of each noise source is quantified; based on the sound energy flow path tracking method, a noise energy propagation path diagram is drawn, the propagation trajectory, energy attenuation law and directivity change of the sound wave after being emitted from the source in the elbow pipe and the external space are qualitatively and quantitatively described, and a noise source spatial distribution model and a noise propagation path model of the elbow pipe structure are generated; the sound power, sound pressure level and radiation directivity data of each dominant sound source in the noise source distribution data are extracted, the total sound power value of the elbow pipe outlet end and the surrounding specific measurement points is calculated, the main noise frequency component is obtained through frequency spectrum analysis, a sound pressure level-frequency variation curve is drawn, the peak frequency and the main frequency band range with energy concentration are identified, the main noise radiation direction and the secondary radiation direction are identified, and the sound energy distribution characteristics in different directions are quantified; the noise level variation law and acoustic hotspot region under different working conditions are predicted.

2. The method of claim 1, wherein, the elbow pipe fluid-structure coupling model is established, and the method further comprises the following steps: Determine the geometric parameters of the elbow according to the requirements of the target application, including the bend radius, pipe diameter size, centerline length of the elbow, wall thickness size and bend angle; Determine the physical property parameters of the fluid, including density, viscosity and Reynolds number range, and determine the material characteristic parameters of the solid constituting the elbow, including the elastic modulus, Poisson's ratio, density, yield strength and internal damping characteristics of the material; Based on the determined geometric parameters and material characteristic parameters, a three-dimensional physical model of the elbow is constructed through parameterized modeling, and the fluid region and the solid region are distinguished during the modeling process, the fluid region is the internal cavity of the elbow, and the solid region is the elbow wall body; For the fluid region, set the inlet velocity boundary condition, volume flow boundary condition, outlet static pressure boundary condition, and no-slip boundary condition on the fluid-solid contact surface; for the solid region, set the fixed end, simply supported or free boundary condition according to the fixing mode and working environment of the elbow; Initialize the fluid field variables, including the initial velocity distribution, initial pressure distribution and turbulence intensity distribution, and initialize the solid field variables, including the initial displacement, initial stress and initial strain; According to the fluid control equation set and combined with the solid control equation set, an elbow fluid-structure interaction model is established, the fluid control equation set includes continuity equation, momentum conservation equation and turbulence model equation, and the solid control equation set includes momentum conservation equation and material constitutive relation.

3. The method of claim 1, wherein, Generate a description model for the propagation characteristics of sound waves in different frequency bands, which further includes: Extract flow field disturbance information, including fluid velocity disturbance, pressure disturbance and turbulent kinetic energy change data; Convert the flow field disturbance information into acoustic source terms and construct an acoustic propagation model, the acoustic source terms include mass source terms, momentum source terms and energy source terms, establish the mathematical expression of the flow-induced acoustic source terms as the input conditions of the acoustic control equation set, the acoustic control equation set includes acoustic wave equation, pressure disturbance equation and potential flow equation; Establish a control equation describing the propagation of small-amplitude sound waves, which includes mass conservation equation, momentum conservation equation and energy conservation equation; in the three-dimensional physical model of the elbow, the acoustic control equation is discretized and the acoustic field is numerically solved.

4. The method of claim 3, wherein, Generate a description model for the propagation characteristics of sound waves in different frequency bands, which further includes: In the numerical solution process, set reasonable boundary conditions, including the acoustic hard boundary condition of the solid surface of the elbow, the free radiation boundary or the sound absorption boundary at the outlet end of the elbow, and obtain the sound pressure distribution diagram, sound pressure level change curve and sound energy spectrum density distribution diagram at different positions inside the elbow; Extract the sound pressure distribution characteristics of different regions of the elbow, identify the sound pressure peak value area, sound pressure node area and sound energy aggregation area; Obtain the energy loss of sound waves when propagating between the curved section and the straight pipe section, combine the sound energy density distribution, draw the sound wave energy flow path diagram, and identify the energy convergence area and the energy dissipation area.

5. The method of claim 1, wherein, Simulate fluid-structure interaction through numerical simulation, which further includes: Based on the fluid-structure coupling model of the elbow and the acoustic propagation model, a multi-physical field joint simulation calculation model is constructed, which is coupled with the fluid dynamics equation, the solid dynamics equation and the acoustic control equation; the fluid velocity field, the pressure field change, the solid displacement field, the stress field distribution and the sound pressure field distribution data at different time steps are output, and the sound pressure time history data in the joint simulation process are recorded; The sound pressure time history data is processed by fast Fourier transform to obtain the frequency domain sound pressure level spectrum; Based on the sound pressure level spectrum, the main noise frequency components and the dominant frequency band are identified, the peak frequency, the primary and secondary frequency distribution and the energy concentration band are extracted; the contribution proportion of different regions in the elbow structure to the overall sound radiation is identified by combining the sound source positioning, the main sound source position is determined, and the noise source distribution data are generated; The sound source intensity distribution map, the dominant frequency change curve and the sound source contribution rate analysis table are output; Based on modal analysis, the local resonance region and the sound wave amplification effect region of the structure are identified.

6. The method of claim 5, wherein, Based on modal analysis, the local resonance region and the sound wave amplification effect region of the structure are identified, which further includes: Through modal analysis, the natural frequency, mode shape and vibration energy distribution characteristics of the elbow structure are extracted, the regions prone to local resonance of the elbow wall under fluid disturbance excitation are identified, and the corresponding resonance frequency and amplitude are quantitatively given; Combined with acoustic modal analysis, the standing wave zone and amplification zone of sound wave formed in the specific structure form of the elbow are identified, and the contribution of sound wave standing effect to the overall sound pressure level gain is quantitatively described; The local resonance mode distribution map, the sound standing wave mode diagram and the sound energy gain distribution curve are generated.

7. The method of claim 1, wherein, Predicting the noise level variation law and the acoustic hot spot region under different working conditions, which further includes: Based on the simulation calculation results of multiple groups of typical working conditions, the noise power, sound pressure level and frequency spectrum change data corresponding to each working condition are extracted, and the typical working conditions are set by different flow rates, pressures and vibration characteristics; The response curve of noise level with flow rate change and geometric structure parameter change is established, and the trend of noise change with working condition is quantitatively described; By comparing the sound source distribution characteristics and energy aggregation under different working conditions, the acoustic hot spot region formed under each working condition is identified, which includes the sound energy aggregation zone, the sound pressure peak zone and the sound wave standing enhancement zone; The sound pressure distribution cloud map, the sound source position change map and the sound power change trend table under the typical working condition are output.

8. The method of claim 1, wherein, Determine the best structure combination through repeated iteration simulation, which further includes: Based on the noise source spatial distribution model and the noise propagation path model, the high noise region with the most concentrated noise energy and the strongest sound radiation in the elbow, and the high frequency excitation region prone to high frequency local vibration in the elbow are identified; For the high noise region, the ratio of the bending radius to the diameter of the elbow is optimized, the wall thickness distribution at the elbow is adjusted, and the local curvature change is optimized; a buffer zone is added in the high flow rate change region inside the elbow, the pipe diameter is locally enlarged and the slow transition section is increased, and the flow line guiding structure is arranged at the inlet and outlet of the elbow; composite materials, damping materials or sandwich structures are used in the high frequency excitation region, and the material thickness and structure level are arranged according to different regions; Iterative simulation is performed to obtain the overall flow stability of the elbow, the turbulence intensity, the local sound pressure peak variation, the noise radiation level, the flow field uniformity, the turbulent kinetic energy, the turbulent dissipation rate, the wall vibration amplitude, the resonance frequency, the sound energy amplification effect and the high-frequency noise level; Based on the iterative simulation results, iterative simulation is repeatedly performed until the optimal structure combination is determined.

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