PDF - Infolytica Engage

From Electromagnetic Forces to Acoustics:
Full Chain Analysis for Vibro-Acoustic Studies with
Electromagnetic Excitations
Fraunhofer Institute for Algorithms and
Scientific Computing SCAI
Dipl. Math.-techn. Nadja Wirth
27.10.2015
© Fraunhofer SCAI
Fraunhofer Society
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
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
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Institute for Algorithms and Scientific Computing
 High Performance Computing
 Optimization in production, logistics and design
 Data Mining and information extraction
 Network analysis
 Numerical simulation
Division Multiphysics
 MpCCI CouplingEnvironment
 Mapping tool MpCCI FSIMapper for loads and boundary conditions
 Mapping tool MetalMapper for material properties induced by forming and stamping
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Content
Motivation

Electromagnetic forces acting to the structure

Vibration and acoustics
MpCCI FSIMapper

Functionality and Features

General mapping process
Example

24-slots motor

Mapping of electromagnetic forces

Vibration and acoustic simulation using MSC.Nastran and MSC.Actran
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Motivation
General Problem Description

Electromagnetic field produces forces acting to the structure

Forces deform the structure

Periodically repeating forces excite vibrations of the structure

Periodically vibrating structure produces noise in its surrounding air
Simulation Tools
MagNet
FSIMapper
MSC.Nastran
MSC.Actran
Simulation of
electromagnetic forces
Data transfer
Simulation of structural
deformations and
vibrations
Simulation of
acoustics
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MpCCI FSIMapper
General
Purpose
 Transfer data from a simulation result (“source”) to a second simulation (“target”) as boundary
condition
Features
 Simple file-based tool

Target
Source
FSIMapper
Codes:
•
•
•
•
Fluent (.cas, .dat)
FINE/Turbo (.cgns)
Ensight .case
FloTHERM, FloEFD
Quantities:
• temperature, heat transfer
coefficient, heat flux
• pressure
Analyses:
• harmonic
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Features:
Mapping supports
• different mesh densities
and orders
• different geometries
(orphan handling)
• different unit systems
• different model positions
• Fourier transformation
• periodic models
Codes:
Analyses:
MpCCI FSIMapper
Procedure for Simulating Electro-Magnetic-Induced Vibrations
Simulate
Source
Model
Export
Surface
Force
Density
Source
Result
Perform
Mapping
Target
Mesh
Build
Target
Mesh
© Fraunhofer SCAI
Define
Mapping
Surface
Electromagnetic
Forces
Perform
Target
Simulation
Example
coils
stator
4-Pole-24-Slots-Motor
Motor Configuration
Periodic quarter model in MagNet
 Stator
• 24 slots (total)
 Rotor
• 4 poles (total)
• rotation speed 10.8 ° 𝑚𝑠 = 1800 𝑟𝑝𝑚 = 30 𝐻𝑧
• Interior permanent magnet
 Coils
• 35 turns
• odd parity
rotor
magnet
Source Analysis

Transient 3D with Motion
case
Target Analyses

Stator vibrations excited by the electromagnetic
forces

Resulting noise in surrounding air
stator
flange
© Fraunhofer SCAI
air
Structural Vibration Analyses
Description
Method

Linear Equations of Motion

Transformation to Frequency Domain
𝑀 𝑥 + 𝐷𝑥 + 𝐾 𝑥 = 𝑓
𝑥 displacement
𝑓 force
with
 consider steady state condition (without the initial phase of attack)
 Frequency Response Analysis:
Force at frequency Ω:
Response at frequency Ω:
𝑓 =𝑏∙𝑒
𝑖 Ω𝑡+𝜗
𝑥 =𝑎∙𝑒
𝑖(Ω𝑡+𝜑)
𝑖𝜗
𝑖 Ω𝑡
𝑖𝜑
𝑖 Ω𝑡
= 𝑏𝑒 ∙ 𝑒
𝑓∈ℂ
= 𝑎𝑒 ∙ 𝑒
𝑥∈ℂ
𝑀 mass matrix
𝐷 damping matrix
𝐾 stiffness matrix
𝜑
𝑎
𝒂 ∙ 𝒆𝒊(𝜴𝒕+𝝋)
1
Ω
 Linear superposition of all single oscillation responses (at each exciting frequency component Ω) leads to the full
response
Fourier Transformation (discrete)

Transient 𝑆𝐹𝐷 → Frequency Spectrum

Input for Vibration Analysis

Done by FSIMapper
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MpCCI FSIMapper
Create Source Simulation File
Simulate
Source
Model
Export
Surface
Force
Density
Source
Result
Perform
Mapping
Target
Mesh
Build
Target
Mesh
© Fraunhofer SCAI
Define
Mapping
Surface
Electromagnetic
Forces
Perform
Target
Simulation
Example
Source Simulation
MagNet Simulation
 Transient 3D with Motion
• ¼ turn
• 180 time steps
• Fourier transformation: constant time steps
 Flux Density 𝐵
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 Surface Force Density: 𝑆𝐹𝐷~𝐵2
Example
Export Surface Force Density
MagNet Exporter

Export Surface Force Density 𝑆𝐹𝐷

Select component „Stator“ from MagNet‘s object tree

Open exporter by
Extensions→Exporter for MpCCI
Exported File

ASCII file SFD-Stator.vtk

Contains
Source
Result

Surface mesh of the stator

𝑆𝐹𝐷 for 180 time steps:
•
First: 0 ms
•
Time step size: 0.046296296 ms
•
Last: 8.287037037 ms
•
automatically truncated for Fourier transformation
without Windowing
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MpCCI FSIMapper
Create Target Mesh File
Simulate
Source
Model
Export
Surface
Force
Density
Source
Result
Perform
Mapping
Target
Mesh
Build
Target
Mesh
© Fraunhofer SCAI
Define
Mapping
Surface
Electromagnetic
Forces
Perform
Target
Simulation
Example
Target Mesh
MSC.Nastran Mesh
 Solid model of the full stator ()
• Second order tetra elements
• Independent to MagNet mesh
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
Surface Elements ()
• Define the mapping surface
• Use the same node ID‘s

MSC.Nastran Deck
• ASCII file stator_surface.bdf
Target
Mesh
MpCCI FSIMapper
Map Surface Force Density from Source to Target
Simulate
Source
Model
Export
Surface
Force
Density
Source
Result
Perform
Mapping
Target
Mesh
Build
Target
Mesh
© Fraunhofer SCAI
Define
Mapping
Surface
Electromagnetic
Forces
Perform
Target
Simulation
Example
FSIMapper Settings
Source
Result
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Target
Mesh
Example
FSIMapper Settings
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Example
FSIMapper Settings
© Fraunhofer SCAI
Example
FSIMapper Settings
© Fraunhofer SCAI
Example
FSIMapper Settings
Electromagnetic
Forces
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Example
Mapping Results
original
Periodic Mapping
 FSIMapper creates the full MagNet surface
mesh from the quarter section
constant
 The data are copied constantly to the sections
building the full model
Transient Mapping
original
 For each time step 𝑆𝐹𝐷 is mapped
Results of Fourier Transformation

MSC.Nastran Deck:
• stator_surface-mapped_FreqRespForce.bdf
• Real and imaginary part of the force for each
frequency and node
• Frequency range: 0 to 10800 Hz in 120 Hz
steps
• Values at 0Hz represent the time-average
 Visualization:
• stator_surface-mapped_FreqRespForce.ccvx
• Complex force represented by 10 pseudo
time steps
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Electromagnetic
Forces
complex force amplitude:
𝑓 = 𝑏 ∙ 𝑒 𝑖𝜗
IFFT with 𝑛 pseudo time steps:
𝑓𝑘 = 𝑏 ∙ cos 2𝜋 ∙ 𝑘 𝑛 + 𝜗 , 𝑘 = 1, … , 𝑛
Example
Mapping Results
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Example
Mapping Results
© Fraunhofer SCAI
MpCCI FSIMapper
Vibration and Acoustic Analysis of the Stator
Simulate
Source
Model
Export
Surface
Force
Density
Source
Result
Perform
Mapping
Target
Mesh
Build
Target
Mesh
© Fraunhofer SCAI
Define
Mapping
Surface
Electromagnetic
Forces
Perform
Target
Simulation
Example
Target Simulation
$NASTRAN BUFFSIZE=65537
$
SOL 111 $ Modal Frequency Response
CEND
$
TITLE = ElectromagneticExcitation
$
METHOD = 10
SPC = 1
FREQ = 601
DLOAD = 600
DISP(PLOT) = ALL
STRESS(PLOT)=ALL
RESVEC = NO
ECHO = NONE
$-------2-------3-------4-------5-------6------BEGIN BULK
$
EIGRL
10
0.
500
$
INCLUDE 'CaseFlangeStator.bdf'
INCLUDE 'stator_surface-mapped_FreqRespForce.bdf'
$
PARAM, POST, -1
PARAM, ALPHA2, 1e-2 , 0.0
$
ENDDATA
© Fraunhofer SCAI
Model
Electromagnetic Forces
Thank you for your
attention!
contact: [email protected]
Fraunhofer Institute for Algorithms and Scientific Computing SCAI
Schloss Birlinghoven
53757 Sankt Augustin
Germany
© Fraunhofer SCAI