ANSYS_Mechanical_APDL_Acoustic_Analysis_Guide

【实例截图】

【核心代码】

Table of Contents
1. Introduction to Acoustic Analysis ........................................................................................................... 1
1.1.The General Acoustic Equations ........................................................................................................ 1
1.2. Overview of the Acoustic Analysis Process ......................................................................................... 2
2. Using the Acoustic Analysis Tools ........................................................................................................... 5
2.1. Elements Used in an Acoustic Analysis ............................................................................................... 5
2.2. Commands Used in an Acoustic Analysis ........................................................................................... 7
2.3. Understanding Acoustic Analysis Terminology .................................................................................. 8
2.4. Acoustic Analysis Resources and Examples ........................................................................................ 9
3. Modeling for an Acoustic Analysis ........................................................................................................ 11
4. Defining the Acoustic Modeling Environment ..................................................................................... 13
4.1. Defining Element Types .................................................................................................................. 13
4.2. Specifying the System of Units ........................................................................................................ 14
5. Defining Acoustic Material Properties .................................................................................................. 17
5.1. Basic Material Parameters of Acoustic Media .................................................................................... 17
5.2. Non-Uniform Ideal Gas Material ...................................................................................................... 18
5.3. Perforated Material ......................................................................................................................... 19
5.3.1. Equivalent Fluid Model of Perforated Material ......................................................................... 19
5.3.2. Poroelastic Acoustic Material .................................................................................................. 21
5.4.Viscous-Thermal Materials ............................................................................................................... 22
5.4.1. Acoustic Propagation in the Viscous Fluid ............................................................................... 22
5.4.2. Boundary Layer Impedance (BLI) Model .................................................................................. 22
5.4.3. Low Reduced Frequency (LRF) Model ..................................................................................... 23
5.4.4. Full Linear Navier-Stokes Equations (FLNS) Model ................................................................... 23
5.5. Material Properties for Room Acoustics ........................................................................................... 24
6. Specifying Acoustic Analysis Region Attributes and Meshing ............................................................. 25
7. Applying Boundary Conditions in an Acoustic Analysis ....................................................................... 27
7.1. Applying Boundary Conditions ....................................................................................................... 27
7.1.1. Pressure Boundary ................................................................................................................. 28
7.1.2. Rigid Wall Boundary ............................................................................................................... 28
7.1.3. Surface Impedance Boundary ................................................................................................. 28
7.1.4. Free Surface (Sloshing Effect) .................................................................................................. 30
7.1.5. Symmetric Plane in Viscous-Thermal Acoustics ....................................................................... 30
7.1.6. Sliding Surface in Poroelastic Acoustics ................................................................................... 30
7.1.7. Pervious Porous Surface in Poroelastic Acoustics ..................................................................... 31
7.2. Absorbing Boundary Condition (ABC) .............................................................................................. 31
7.3. Artificially Matched Layers .............................................................................................................. 32
7.3.1. Perfectly Matched Layers (PML) .............................................................................................. 33
7.3.2. Irregular Perfectly Matched Layers (IPML) ................................................................................ 37
7.4. Floquet Periodic Boundary Condition (FPBC) ................................................................................... 39
7.4.1. Floquet Boundary Condition for Harmonic Analysis ................................................................ 40
7.4.2. Floquet Boundary Condition for Modal Analysis ...................................................................... 41
7.4.2.1. Frequency as Eigenvalue Solution .................................................................................. 41
7.4.2.2. Phase Shift as Eigenvalue Solutions ................................................................................ 41
8. Applying Excitation Sources and Loads in an Acoustic Analysis .......................................................... 43
8.1. Applying Acoustic Excitation Sources .............................................................................................. 43
8.1.1. Pressure or Energy Density Excitation ..................................................................................... 44
8.1.2. Outward Normal Velocity (Acceleration) Excitation .................................................................. 45
8.1.3. Arbitrary Velocity (Acceleration) Excitation .............................................................................. 45
8.1.4. Analytic Incident Wave Sources .............................................................................................. 47
iii
Release 2020 R2 - © ANSYS, Inc. All rights reserved. - Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.
8.1.5. Mass Source, Mass Source Rate, or Power Source ..................................................................... 48
8.1.6. Random Excitation with Diffuse Sound Field ........................................................................... 49
8.1.7. Specified Mode Excitation in an Acoustic Duct ........................................................................ 52
8.1.8. Force Potential for Mean Flow Effect ....................................................................................... 53
8.1.9. Excitation Sources in Viscous-Thermal Acoustics ..................................................................... 53
8.1.9.1. Nodal Velocities ............................................................................................................. 53
8.1.9.2. Nodal Temperature ........................................................................................................ 53
8.1.9.3. Surface Pressure ............................................................................................................ 54
8.1.9.4. Surface Shear Viscous Force ........................................................................................... 54
8.1.9.5.Volumetric Force Density ............................................................................................... 54
8.1.9.6. Surface Heat Flux ........................................................................................................... 54
8.1.9.7.Volumetric Heat Source ................................................................................................. 55
8.1.10. Excitation Sources in Poroelastic Acoustics ............................................................................ 55
8.1.10.1. Imposed Pressure ........................................................................................................ 55
8.1.10.2. Imposed Displacement ................................................................................................ 55
8.1.10.3. Surface Shear Force ..................................................................................................... 56
8.2. Applying Acoustic Loads ................................................................................................................. 56
8.2.1.Trim Element with Transfer Admittance Matrix ........................................................................ 57
8.2.2. Impedance Sheet ................................................................................................................... 59
8.2.3. Equivalent Surface Source ...................................................................................................... 60
8.2.3.1. Flagging an Equivalent Source Surface ........................................................................... 60
8.2.4. Surface Port ........................................................................................................................... 61
8.2.5. Mean Flow Effect .................................................................................................................... 62
8.2.6. Ambient Temperature ............................................................................................................ 62
8.2.7. Quiescent Pressure ................................................................................................................. 62
9. Accounting for Acoustic Fluid-Structure Interaction (FSI) .................................................................... 63
9.1. Matrix-Coupled FSI Solutions .......................................................................................................... 63
9.2. One-Way Coupling FSI Solutions ..................................................................................................... 64
10. Solving an Acoustic Analysis ............................................................................................................... 65
10.1. Acoustic Analysis Solution Settings ............................................................................................... 65
10.1.1. Modal Analysis Settings ........................................................................................................ 65
10.1.2. Harmonic Analysis Settings .................................................................................................. 66
10.1.2.1. Full Harmonic Analysis ................................................................................................. 66
10.1.2.1.1. Setting the Analysis Frequencies ......................................................................... 67
10.1.2.1.2. Specifying the Analysis Solver ............................................................................. 67
10.1.2.1.3. Selecting the Scattered Formulation for Harmonic Analysis .................................. 68
10.1.2.1.4. Defining Revolutions per Minute (RPM) During a Multi-Load Solution .................. 68
10.1.2.2. Mode-Superposition Harmonic Analysis ....................................................................... 69
10.1.3.Transient Analysis Settings .................................................................................................... 70
10.1.4. Spectrum Analysis ................................................................................................................ 71
10.1.5. Steady-State Analysis Settings .............................................................................................. 71
10.2. Starting and Finishing the Solution ................................................................................................ 71
11. Using Advanced Solution Techniques in an Acoustic Analysis ........................................................... 73
11.1. One-Way Coupling from Single Physics to Acoustics ...................................................................... 73
11.1.1. One-Way Coupling from Structure to Acoustics ..................................................................... 74
11.1.2. One-Way Coupling from ANSYS Fluent to Mechanical APDL Acoustics for Cabin Noise ........... 76
11.2. Linear Perturbation in an Acoustic Application .............................................................................. 78
11.3. Solving the Convective Wave Equation for the Mean Flow Effect .................................................... 80
11.4. Solving the Diffusion Equation for Room Acoustics ........................................................................ 82
11.5. Using Cyclic Symmetry with Fluid-Structure Interaction ................................................................. 84
11.5.1. Acoustic Boundary Conditions and Loads ............................................................................. 84
Release 2020 R2 - © ANSYS, Inc. All rights reserved. - Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates. iv
Acoustic Analysis Guide
11.5.2. Cyclic Fluid-Structure Interaction Example ............................................................................ 85
11.6. Full Linear Navier-Stokes Equations Model (FLNS) .......................................................................... 86
11.7. Poroelastic Acoustics ..................................................................................................................... 88
11.8. Using Contact Elements in Acoustic Analysis .................................................................................. 90
11.9. Acoustic Equivalent Circuit Analogous to Electrical Circuit .............................................................. 91
12. Postprocessing Acoustic Analysis Results .......................................................................................... 93
12.1. Helpful Postprocessing Commands ............................................................................................... 93
12.2. Postprocessing a Harmonic Acoustic Analysis ................................................................................ 94
12.2.1. Reviewing Analysis Results ................................................................................................... 94
12.2.2. Calculating Near Fields, Far Fields, and Far-Field Parameters ................................................... 95
12.2.2.1. Accounting for Model Symmetry .................................................................................. 96
12.2.2.2. Radiation Solid Angle .................................................................................................. 96
12.2.2.3. Near Sound Pressure Field ............................................................................................ 97
12.2.2.4. Far Sound Pressure Field and Far-Field Parameters ........................................................ 97
12.2.2.5. Far-Field Microphone ................................................................................................... 97
12.2.2.6. Radiated Far-Field of a Vibrating Panel .......................................................................... 98
12.2.3. Calculating Acoustic Propagation Parameters ....................................................................... 98
12.2.4. Calculating Acoustic Surface Quantities ................................................................................ 99
12.2.5. Calculating Acoustic Volumetric Quantities ......................................................................... 100
12.3. Postprocessing a Modal Acoustic Analysis .................................................................................... 101
12.4. Postprocessing a Transient Acoustic Analysis ............................................................................... 101
13. Acoustic Analysis Examples .............................................................................................................. 103
13.1. Example: Acoustic-Structural Coupled Modal Resonance of an Annular Ring Submerged in Water
with a Harmonic Analysis .................................................................................................................... 103
13.2. Example: Resonant Frequencies in a Pipe with Ideal Gas ............................................................... 105
13.3. Example: Acoustic Harmonic Response in a Room ........................................................................ 106
13.4. Example:Transmission Loss of a Muffler ....................................................................................... 108
13.5. Example: Johnson-Champoux-Allard Model of a Perforated Material ............................................ 109
13.6. Example:Transfer Admittance Matrix in Fluid ............................................................................... 111
13.7. Example: Boundary Layer Impedance Model of a Rigid Walled Waveguide with Viscous-Thermal
Fluid ................................................................................................................................................... 113
13.8. Example: Radiation from Two Waveguides ................................................................................... 114
13.9. Example: Radiation from a Dipole ................................................................................................ 116
13.10. Example: Monopole Incident Wave Scattering of a Rigid Sphere ................................................. 118
13.11. Example: Planar Incident Wave FSI Scattering of an Infinite Cylindrical Shell ................................ 119
13.12. Example: One-Way Coupling from Structure to Acoustics ........................................................... 122
13.13. Example: Modal Analysis of an Acoustic-Structural Coupled Structure with Nonlinear Static Prestress
Using Linear Perturbation ................................................................................................................... 124
13.14. Example: Spectrum Analysis of a Cylindrical Tank Filled with Water ............................................. 125
13.15. Example: Structural Panel Subject to Excitation From a Diffuse Sound Field ................................. 127
13.16. Example:Transmission Loss of a Structural Panel under an Obliquely Incident Plane Wave .......... 130
13.17. Example: Sound Far Field from a Piston Using Rayleigh Integral .................................................. 132
13.18. Example: Acoustic Propagation in a Lined Guide with an Impedance Boundary and Mean Flow ... 133
13.19. Example: Sound Transmission Between Coupled Rooms Through a Partition Wall ....................... 137
13.20. Example: Full Linear Navier-Stokes (FLNS) Model for a Thin Gap .................................................. 139
13.21. Example: Surface Impedance for a Multilayer Poroelastic Material ............................................... 142