Acoustic Absorber dialog box (Acoustics Transient BEM)

Type
Type	Specifies the acoustic absorber.Admittance/Impedance Coefficients — Lets you specify a constant complex excitation with real and imaginary parts, constant complex excitation with magnitude and phase angle, or a complex field value that is frequency dependent.Damping and Stiffness Coefficients — Lets you specify an equivalent structural damping and equivalent structural stiffness.
Name
Name	Specifies the name of the acoustic absorber.
Description	Specifies the description for the acoustic absorber.
Destination Folder
Simulation Object Container	Specifies the folder in the Simulation Navigator in which to store the new acoustic absorber.The list includes the root container and folders that you created using the New Folder command in the Simulation Object Container.
Folder Manager	Displays a hierarchical list of folders.To create a new folder, right-click any level of the hierarchy and choose New Folder.
Model Objects / 2D Fluid Elements
	Defines the support for the absorbent panel. You can select it by using the Faces To Create Acoustic Absorber On command for faces of solid fluid elements or by referring to an existing group that contains faces of solid fluid elements.Note: The Simcenter 3D Acoustics BEM solver environment supports only fluid 2D elements.
Group Reference	Lets you select the groups of free faces of fluid elements to apply acoustic absorber.For more information, see Group Reference options.
Select Object	Lets you select the geometry or FE entities on which to apply the acoustic absorber property.Excluded:Lets you remove individual entities from within the selected object.
Stacked Smart Selector Methods	Opens the Smart Selector Methods dialog box where you can specify a progression of smart selection filters.For more information, see Smart Selector Methods dialog box.
Magnitude	Sets the Magnitude Type as Admittance or Impedance
Admittance
Available when Type is set to Admittance.
Admittance	Specifies how the admittance value is defined.This is the boundary definition with acoustic admittance defined as a complex number. You can specify a constant value or frequency-dependent value.
Real	Available when Admittance is set to Real/Imaginary.Sets the real component.
Imaginary	Available when Admittance is set to Real/Imaginary.Sets the imaginary component.
Magnitude	Available when Admittance is set to Magnitude/Phase.Sets the magnitude value.
Phase	Available when Admittance is set to Magnitude/Phase.Sets the phase angle value.
Specify Field	Available when Admittance is set to Field.Specifies a complex field that is frequency dependent.
Impedance
Available when Type is set to Impedance.
Impedance	Specifies how the impedance value is defined.This is the boundary definition with acoustic impedance defined as a complex number. You can specify a constant value or frequency-dependent value.
Real	Available when Impedance is set to Real/Imaginary.Sets the real component.
Imaginary	Available when Impedance is set to Real/Imaginary.Sets the imaginary component.
Magnitude	Available when Impedance is set to Magnitude/Phase.Sets the magnitude value.
Phase	Available when Impedance is set to Magnitude/Phase.Sets the phase angle value.
Specify Field	Available when Impedance is set to Field.Specifies a complex field that is frequency dependent.
Coefficients
Available in the Simcenter Nastran solver environment, when Type is set to Damping and Stiffness Coefficients. It requires Damping and Stiffness coefficients from structure.
Equivalent Structural Damping	Specifies the magnitude of structural damping coefficient.
Equivalent Structural Stiffness	Specifies the magnitude of structural stiffness coefficient.
Magnitude
Type	Available in the Simcenter Nastran solver environment.Impedance — Specifies the magnitude of specific impedance (Z).The unit is kg/(s*m2) for specific impedance.Admittance — Specifies the magnitude of specific admittance (A=1/Z).The unit is s*m2 / kg for specific admittance.Note: You must use a table field of frequency-dependent complex values.
Field
Specify Field	Defines how the field is distributed over the nodes in the selected area.
Select Existing Field from List	Lets you select an existing field.
Formula Constructor	Lets you use a formula to construct a field.For more information, see Create a formula field to define the magnitude of a boundary condition.
Table Constructor	Lets you use a table to construct a field.For more information, see Create a table field to define the magnitude of a boundary condition and Create a table field to define a material property.
Link Constructor	Lets you reference an existing field. You can override the field's spatial map to use the field in another location.For more information, see Linked Field dialog box.
Plot (XY)	Plots the field as an XY graph.For more information, see: Plotting functions, Interpreting the graph, and Editing graph display options.
Overlay (XY)	Available when a plot is already displayed.Overlays a plot on an existing plot. You can overlay up to 50 plots.For more information, see Overlay plots.
Distribution
These options are available in the Simcenter Nastran solver environment.
Method	Defines how the field is distributed over the selected objects.Constant: Distributes the field as a constant value across the selected objects.A field is always mapped to global or Cartesian coordinates, even if it was defined in cylindrical or spherical coordinates.
Output	The absorbent panel is displayed on the model with small cones on the element faces of the support, for example:The software checks that all selected faces contain only fluid nodes (that is, nodes of elements that have a fluid material).The relevant CAABSF and PAABSF bulk data entries are connected through their PID field.Note: When you define specific admittance, you must invert the complex values to get the specific impedance.
These options are available in the Simcenter 3D Acoustics BEM solver environment.
Fluid Element Side Selection
Side Selection	Available for indirect BEM acoustic and vibro-acoustic solutions.Specifies the side of the fluid elements of the acoustic mesh on which to apply the acoustic absorber property.Top — Applies the acoustic absorber to the top (positive) side of the fluid elements of the acoustic mesh.Bottom — Applies the acoustic absorber to the bottom (negative) side of the fluid elements of the acoustic mesh.Top and Bottom — Applies the acoustic absorber to the top (positive) and bottom (negative) side of the fluid elements of the acoustic mesh.
Type
Type	Specifies the admittance, impedance, or evenly distributed characteristic impedance type.
Admittance Value
Available when Type is set to Admittance.
Admittance	Specifies how the admittance value is defined.This is the boundary definition with acoustic admittance defined as a complex number. You can specify a constant value or frequency-dependent value.
Real	Available when Admittance is set to Real/Imaginary.Sets the real component.
Imaginary	Available when Admittance is set to Real/Imaginary.Sets the imaginary component.
Magnitude	Available when Admittance is set to Magnitude/Phase.Sets the magnitude value.
Phase	Available when Admittance is set to Magnitude/Phase.Sets the phase angle value.
Specify Field	Available when Admittance is set to Field.Specifies a complex field that is frequency dependent.
Impedance Value
Available when Type is set to Impedance.
Impedance	Specifies how the impedance value is defined.This is the boundary definition with acoustic impedance defined as a complex number. You can specify a constant value or frequency-dependent value.
Real	Available when Impedance is set to Real/Imaginary.Sets the real component.
Imaginary	Available when Impedance is set to Real/Imaginary.Sets the imaginary component.
Magnitude	Available when Impedance is set to Magnitude/Phase.Sets the magnitude value.
Phase	Available when Impedance is set to Magnitude/Phase.Sets the phase angle value.
Specify Field	Available when Impedance is set to Field.Specifies a complex field that is frequency dependent.
Spatial Distribution (%)
Available when Type is set to Evenly Distributed Characteristic Impedance.Evenly Distributed Characteristic Impedance is available for indirect BEM acoustic and vibro-acoustic solutions.
Spatial Distribution (%)	Move the slider to the right, or type a floating precision value from 1% through 100%.

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Acoustic Absorber dialog box (Acoustics Transient BEM), Simcenter 3D 2021.1 Series

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