Answers for industry LMS Virtual.Lab Boundary Elements Acoustics [VL-VAM.35.2] 13.1 Benefits Accurate modelling of infinite domain acoustic problems Fast and efficient solvers Modeling effort is limited as only the boundary needs to be modeled Features Implements both indirect and direct BEM formulation Can perform both weakly coupled and strongly coupled vibro-acoustic response simulations Supports a wide variety of acoustic sources and properties Computation acceleration due to integrated Pade Expansion algorithms for harmonic analysis Summary Acoustic Harmonic BEM Solver is the enabling tool, which allows the user to solve acoustic radiation models using the Boundary Element Method. This method predicts the acoustic response in both enclosures and unbounded domains and requires a mesh of the surface bounding the fluid domain only, resulting in a very low number of degrees of freedom. The user specifies a frequency range and intermediate steps, with no constraints on either: different ranges and steps can be combined. A choice of solvers is included, with automatic switching between in- and outof-core methods depending on the problem size and computer resources available. Acoustic boundary element models can be excited by a set of sound sources in the domain or by imposed normal surface velocities or surface pressures on the boundary. These boundary conditions can be imported from vibration tests or from structural FEA codes or using generic values. Acoustic damping is introduced through surface impedance boundary conditions. The method yields acoustic results at any field point and features dedicated post-processing tools to get insight into the noise mechanisms. Capabilities BEM Harmonic Acoustic and Vibro- Acoustic Solver Element Properties Structural model characterized by structural modes Imported from external files
Computed using standard FE drivers Acoustic fluid, characterized by a sound velocity and fluid density Frequency-dependent sound velocity and fluid density Complex sound velocity Complex fluid density (in BEM Direct Element option) Absorbent Panels, characterized by an impedance or admittance boundary condition on elements Complex, constant or frequency dependent values Discontinuous impedance/admittance on elements in the indirect method (each element side may be assigned a different value) Rigid Transfer admittance relations between element faces (complex and frequency-dependent values). Acoustic Boundary conditions Pressure boundary conditions on elements Constant values Frequency Functions Distributed values (vector format) from solutions sets or external files Vibration boundary conditions on elements Constant values Frequency Functions Distributed values (vector format) from solutions sets or external files Discontinuous boundary conditions on elements in the indirect method (each element side may be assigned a different boundary condition) Displacement, velocity or acceleration Projection of structural vibration results from an incompatible mesh, with four different algorithms Projection matrix can be updated by the user Automatic creation of junction constraint conditions in the indirect method Automatic creation of free edges constrains in the indirect method Aeroacoustic Surface Dipoles (requires Aero-Acoustic Modeling VL-ACM.41.3) Acoustic Sources Spherical sources Plane wave sources Distributed Plane waves (for acoustic diffuse field) Cylindrical sources Constant or Frequency-dependent characteristics Distributed quadrupole sources (requires Aero-Acoustic Modeling VL- ACM.41.3) Fan source (requires Aero-Acoustic Modeling VL-ACM.41.3) Structural Modes Import from multiple data source: From external files From standard FE driver A modal editor is available on the mode set, allowing to: Editing of frequency, damping, modal mass on range of selected modes (single mode / multiple modes) Adding annotation to modes, e.g. a description. Select/de-select modes Computing global/local indicator per mode and sorting the modes.
Structural Boundary Conditions Discrete Structural force Defined with Load Function Set (Function format) Support of structural excitation on an incompatible mesh Force along specific axis or normal component Import from MS Excel Import from external data source (LMS CADA-X ) Scale / add off-set / invert sign Distributed Pressure loading Defined with Load Vector Set (Vector format) Support of structural excitation on an incompatible mesh Import from other solutions or data file Methods Boundary element formulation Indirect Variational Direct Element Collocation Direct Node Collocation (for coupled problems) Acoustic Transfer Vector (ATV) Computation (requires VL- ACM.32.3) Forced frequency response Standard uncoupled or strongly coupled ATV-based (requires VL-ACM.32.3) Asymptotic approximation methods (Rayleigh Integral and Plane Wave Approximation) Multiple Symmetry and/or antisymmetry planes User-selectable boundary element integration quadrature Modal superposition, using physical acoustic model and structural modes, with viscous or structural Storage of Frequency Response Functions at a selection of nodes or field Coupled Noise Transfer Function (NTF) analysis Modal approach (modal coordinates) Modal Superposition, using the real modes, with viscous or hysteretic Storage of Frequency Response Functions at a selection of field Vibro-Acoustic Transfer Vectors (VATV) Modal approach (modal coordinates) Modal Superposition, using the real modes, with viscous or hysteretic Contains the sensitivity of sound pressure level at microphone to structural pressure loading on structural surfaces Pressure responses can be obtained by using the VATV in a VATV Response Case (VL-HEV.21.1) or VATV Random Response Case (VL- NVP.20.3) Coupled structural modes Computed from dry structural modes and acoustic cavity modes Coupled modes frequencies and mode shapes Contribution of uncoupled modes to each coupled mode. Fast solver technology Matrix assembly and solution with in-core and out-of-core solver Automatic optimal blocksize selection for out-of-core solver
Matrix or frequency level parallelization (requires VL-AMP.06.3 for more than 4 processes) Load balancing for frequency level parallelization: frequencies are dynamically assigned to the running processes (instead of an upfront assignment) High Speed BEM (PADE expansion): Conventional assembly of the acoustic system matrix is done only for a set of master frequencies. The matrices for other frequencies are found by interpolation. This increases time performance The acoustic response is approximated around a set of expansion frequencies using Padé function approximants, which allows for faster solutions in case of very high frequency resolution requested for the response Supported for IBEM uncoupled, single load case multi-threaded all acoustic boundary conditions and sources are supported Field-point post-processing Post-processing of acoustic field variables at any location in the BE domain Restart for additional field Evaluation of power radiated through a field point mesh Surface pressure evaluation (Indirect Diffracted field evaluation Faster Post-Processing via Kirchhoff- Helmholtz integral theorem using Multipole Expansion Frequency selector: Single values Frequency sweep Octave band sweep Linear or logarithmic step Frequency interpolation Import frequency list from file or function Data storage: Potentials can be saved in case of re-use. Or alternatively, they are not saved for saving disc space. Structural vibrations can be saved in case of re-use or alternatively they are not saved for saving disc space. Optimized performance and storage through user input and output filters Automatic solver log storage Post-processing Color map Boundary conditions (pressure, velocity and admittance or impedance) Acoustic potentials at all nodes Acoustic pressure at all field (total field or diffracted field only) Particle velocity vector at all field Acoustic Transfer Vectors (requires VL-ACM.32.3) Impedance/Admittance at all field and collocation nodes (Direct Pressure and Power Panel contribution Function displays Acoustic pressure at any field (total field or diffracted field only)
Particle velocity vector at any field Input power Radiated output power (active/reactive) Power through a field point mesh (active/reactive) Radiation efficiency Impedance/Admittance at all field and collocation nodes (Direct Pressure and Power Panel contribution Directivity plots Structural modal participation factors Pre-requisites One of these Desktop products: VL-HEV.21.1 (LMS Virtual.Lab TM Desktop) VL-HEV.22.1 (LMS Virtual.Lab Premium Desktop) VL-MOT.80.1 (LMS Virtual.Lab Motion Desktop). For details of supported hardware, minimum/recommended physical configurations and operating systems, please refer to one of the Desktop product information sheets: LMS Virtual.Lab Desktop (VL- HEV.21.1), LMS Virtual.Lab Premium Desktop (VL-HEV.22.1) or LMS Virtual.Lab Motion Desktop (VL-MOT.80.1). For details on specific configurations (workstation, processor and clock speed, graphics adapters), required service packs and patches, contact your local Siemens PLM Software office. Supported hardware platforms Supported platforms for GUI Windows 32 bit Windows 64 bit Supported platforms for SOLVER Windows XP 64 bit Windows 7 64 bit Linux 64 bit SUSE Linux Entreprise Server (SLES) 11 Red Hat Entreprise Linux (RHEL) 5,6 Ubuntu 12.04 Linux kernel: 2.6.16 Contact Siemens PLM Software Americas +1 248 952-5664 Europe +32 16 384 200 Asia-Pacific +852 2230 3308 2014 Siemens Product Lifecycle Management Software Inc. Siemens and the Siemens logo are registered trademarks of Siemens AG. LMS, LMS Imagine.Lab, LMS Imagine.Lab Amesim, LMS Virtual.Lab, LMS Samtech, LMS Samtech Caesam, LMS Samtech Samcef, LMS Test.Lab, LMS Soundbrush, LMS Smart, and LMS SCADAS are trademarks or registered trademarks of Siemens Industry Software NV or any of its affiliates. All other trademarks, registered trademarks or service marks belong to their respective holders.