MSC.Software EBEA 2012 User’s Guide

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MSC.Software

EBEA 2012 Users Guide

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Corporate Europe Asia Pacifi c

MSC.Software Corporation2 MacArthur PlaceSanta Ana, CA 92707Telephone: (800) 345-2078FAX: (714) 784-4056

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1999.

Revision 0. October 9, 2011

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Instructions for the Energy/BEA program

Introduction

The Energy Finite Element Analysis (EFEA) and Energy Boundary Element Analysis (EBEA)provides a powerful solution for high frequency acoustics. In contrast to traditional FEA solversthat use displacements as the primary variables, the EFEA methods use energy based variableswhich enables noise and vibration simulations at much higher frequencies than those attained byconventional FEA analysis. The EBEA solution provides airborne noise loads for use by the EFEAsolution. The combination of EBEA and EFEA methods can be used to predict the interior noiselevels in a vehicle due to exterior acoustic sources. These new solvers are provided throughcollaboration with Michigan Engineering Services and are provided as a pre-release in MSCNastran 2012.

The Energy/BEA (Energy Boundary Element Analysis) program can be used to calculate the

sound radiation and scattering from an arbitrary structure in free or half space at high frequency. Inthe current version, for the half space problem, the boundary of the half space is assumed to berigid, and is restricted to bez=0 plane, where z is the 3rd component of the global coordinate. Theeffect of the half space is automatically introduced in the Energy/BEA program. Users dont needto create a model for the half space boundary.

I. Running the Energy/BEA code

Syntax: EBEApname

pname is a user defined project filename, which is used to create a new project and define thenames of the input data files required by Energy/BEA program. The content of a project fileincludes three filenames (one filename on each line). The first filename (first line) defines theParameter Data File; the second filename (second line) defines the Model File which contains theboundary element model; the third filename (third line) defines the Field Point File which containsthe field point mesh. For example, a project name defined as examp1e can include the followingthere lines:

datamodel_smodel_f

In the fileexamp1e, the Parameter Data is defined in the file data; the Model is defined in the file

model_s; and the Field Points are defined in the file model_f.

I I. Energy/BEA program input data files and required input formatThe Energy/BEA program requires three input data files: Parameter Data File, Model File, andField Point File. The nodes and the elements are in NASTRAN fixed short format. All otherentries are in free format with at least one space separating two adjacent fields. The length of aninput entry in any of the input data files must not exceed 80 characters. The function and therequired input format of each file are defined as follows:

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Parameter Data FileThe name of this file is defined in the first line of the project file (see Section I). This file includesinformation about the frequencies, the speed of sound in the fluid, the density of fluid, the location& strengths of acoustic energy sources, and other control parameters forEnergy/BEA simulation.

FREQ f1 f2 f3 f4Specifies the value of the frequencies at which analysis is required. Up to four frequenciescan be specified on one line. If the number of frequencies exceeds four, repeated lines ofFREQ should be used.

fi The frequency value in Hz. [float]SPEED cSpecifies the speed of sound in the acoustic medium.

c The value of the speed (m/s). [float]

RHO rho

Specifies the density of the acoustic medium.rho The value of the density (kg/m 3). [float]

UNIT unitSpecifies the unit of length used to describe the mesh. If the meter is used as the unit oflength, this entry is not required. This card is only related to the unit of the mesh.For allother quantities, such as speed (m/s), density (kg/m 3), as well as strength (m 6/s 2) andtotal power (W) of the acoustic energy source, the units have to be specified usingInternational System of Units (SI). And the entry in the UNIT card will not affect the units ofother quantities than the length of the mesh.

unit =0, using meter (default). [int]=1, using centimeter. [int]=2, using millimeter. [int]

HALFActivates the half space analysis.

(By default, the free space formulation is used)

SUBCASE sidDefines the load case information (e.g. source information) for each frequency. This entrymust be followed by one or several SOURCE or POWER entries to define a load case foreach frequency. Number ofSUBCASE entries should be equal to the total number offrequencies defined in theFREQ entry/entries.

sid Load case ID, which refers to the sequence ID of frequency defined inFREQ entry/entries.

SOURCE xs ys zs stren did1 did2 did3 did4Specifies the location and strength of acoustic energy source and the associated diffractionplane IDs if available (up to 4 diffraction planes can be assigned to one source. If more thanone diffraction plane is assigned to one source, a corresponding diffraction plane ID should

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be specified on theGRID entry for the particular field point in Field Point File, see below).This entry should follow theSUBCASE entry. This entry can be repeated for any numberof acoustic energy sources in one SUBCASE entry (The characters of acoustic energysources can be described either by SOURCE entry which specifies the strength of thesource, or byPOWER entry which specifies the total power of the source).

xs The global x-coordinate of the acoustic energy source. [float]ys The global y-coordinate of the acoustic energy source. [float]zs The global z-coordinate of the acoustic energy source. [float]stren Strength of the acoustic energy source (m 6/s 2). [float]didi Diffraction plane ID, up to 4 diffraction planes can be specified for eachsource.

POWER xs ys zs power did1 did2 did3 did4

Specifies the location and total power of acoustic energy source and the associateddiffraction plane IDs if available (up to 4 diffraction planes can be assigned to one source. Ifmore than one diffraction plane is assigned to one source, a corresponding diffraction planeID should be specified on theGRID entry for the particular field point in Field Point File,see below). This entry should follow theSUBCASE entry. This entry can be repeated forany number of acoustic energy sources in oneSUBCASE entry (The characters of acousticenergy sources can be described either by SOURCE entry which specifies the strength ofthe source, or byPOWER entry which specifies the total power of the source).

xs The global x-coordinate of the acoustic energy source. [float]ys The global y-coordinate of the acoustic energy source. [float]zs The global z-coordinate of the acoustic energy source. [float]power Total power of the acoustic energy source (W). [float]didi Diffraction plane ID, up to 4 diffraction planes can be specified for eachsource.

LOAD loadSpecifies the method of calculating the contributions of acoustic energy sources in eachload case. Two methods can be specified: one is calculating the response of each acousticenergy source separately; another is calculating the response of all acoustic energy sourcesin one load case simultaneously and totally.

load =0, calculating all acoustic energy sources in a load case simultaneously(default). [int]

=1,calculating each acoustic energy source in a load case separately. [int]

DPLANE did n1 n2 n3 n4Defines the diffraction plane for each source if required.

did Diffraction plane ID, which refers to the sequence ID ofSOURCE.ni ID numbers of theDPOINT entries which define the connectivity of the

diffraction plane. [integers]

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DPOINT id xc yc zcDefines the corner locations which specify the diffraction plane.

id A unique (among all DPOINT entries in Parameter Data File) ID number.xc The global x-coordinate of the point. [float]yc The global y-coordinate of the point. [float]

zc The global z-coordinate of the point. [float]

ZFLOOR zfSpecifies the z-coordinate of the plane parallel to the half space boundary (ground). Thefield point responses below this plane will be calculated using 1/r terms.

zf The global z-coordinate [float]

EXP exp

Specifies the exponential index for the energy density calculation for some particular fieldpoints (GRID entry in the Field Point File should be modified as described below).exp Exponential index. [float]

EFEAIf this keyword is present in the parameter data file, then the EBEA analysis computes theacoustic loading on the surface of the boundary element model and generates automaticallyall the necessary PWAVE cards for prescribing the external acoustic excitation for an EFEAsimulation. This option should be used when the EBEA simulation is utilized for providingthe external acoustic loading due exterior acoustic sources for an EFEA analysis.

Model FileThe name of this file is defined in the second line of the project file (see Section I). It is used todefine the boundary element model for Energy/BEA analysis. The node and element informationofEnergy/BEA program is defined in NASTRAN short and fixed format. The user can create amodel in a pre-processing environment of their choice and output the model in NASTRAN format.Existence of duplicate or un-referenced elements is not allowed, while duplicate or un-referencednodes can exist in the model. It is not required to output a NASTRAN model with sequential (andcompacted) node and element numbers. For the half space analysis the boundary of the half spaceis restricted to be thez=0 plane, wherez is the 3rd component of the global coordinate. Coordinatesof the model should be consistent with this restriction. Orientations of all element normalsshould direct towards the exterior acoustic domain.

GRID id xc yc zcDefines each node in the boundary element model

id A unique (among all GRID entries in Model File) ID numberassociated with the node in the field. [integer]

xc The global x-coordinate of the node. [float]

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yc The global y-coordinate of the node. [float]zc The global z-coordinate of the node. [float]

CQUAD4 eid pid n1 n2 n3 n4Defines a linear (4-nodes) quadrilateral element.

eid A unique ID number associated with the element.[integer]pid An arbitrary integer (can be any value).[integer]ni The ID numbers of the nodes comprising the element (the

normal of the element should direct outward). [integers]CTRIA3 eid pid n1 n2 n3

Defines a linear (3-nodes) triangular element.eid A unique ID number associated with the element.[integer]pid An arbitrary integer (can be any value).[integer]ni The ID numbers of the nodes comprising the element (the

normal of the element should direct outward). [integers]Field Point File

The name of this file is defined in the third line of the project file (see Section I). It is usedto define field point information for computing the results by Energy/BEA program. The fieldpoints are defined in NASTRAN short and fixed format. Only the GRID entry is required.

GRID id iex xc yc zc idfid A unique (among all GRID entries in Field point file) ID number associated

with the node in the field. [integer]iex Specifies the exponential index used for the energy density calculation.

(Occupies the 17th ~24th fields of the line)=0 or Blank Default (=2.0) exponential index is used for calculating the

energy density at this field point.=1Using the exponential index specified inEXP entry in Parameter Data

File to calculate the energy density at this field point.xc The global x-coordinate of the node. [float]yc The global y-coordinate of the node. [float]zc The global z-coordinate of the node. [float]idf Specifies the diffraction plane ID used for this field point if theSOURCEentry has more than one diffraction planes specified in the Parameter Data File.(Occupies the 49th ~56th fields of the line)If all SOURCE entries in the Parameter Data File have only one diffraction plane orno diffraction plane at all, this parameter can be blank.

I II . Output of Energy/BEA ProgramTheEnergy/BEA program outputs the results in one result file. The name of this result file

is same as the name of project (see Section I) additional with the extension out. For example, ifthe project name is defined as exam1, the name of its result file is exam1.out. Content of theresult file includes:

Energy density at each field point.

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Magnitude and components of the intensity at each field point.

If the EFEA card is present in the data file, then the output file has the name pwave.out andcontains all the PWAVE cards which define the acoustic loading excitation for an EFEA

simulation. The content of the pwave.out must be included as part of the model-all.dat file forthe EFEA analysis.

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MSC.Software EBEA 2012 User’s Guide