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 Largest organization for applied and industrial Research & Development in Europe 80 R&D Institutes – Natural Sciences & Engineering More than 24000 employees Annual Budget 2.1 Billion Euro Representative offices and R&D branches in the US, Europe, Japan, Asia, … Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI Target Mesh Example FSIMapper Settings © Fraunhofer SCAI Example FSIMapper Settings © Fraunhofer SCAI Example FSIMapper Settings © Fraunhofer SCAI Example FSIMapper Settings Electromagnetic Forces © Fraunhofer SCAI 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 © Fraunhofer SCAI 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 © Fraunhofer SCAI 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: nadja.wirth@scai.fraunhofer.de Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss Birlinghoven 53757 Sankt Augustin Germany © Fraunhofer SCAI
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