Transfer Admittance dialog box (Acoustics Transient BEM)

Name
Name	Sets the name of the transfer admittance simulation object.
Description	Sets a description for the transfer admittance simulation object.
Destination Folder
Simulation Object Container	Specifies the folder in the Simulation Navigator in which to store the transfer admittance boundary condition.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.
Surface on 2D Fluid Elements
Select Object	Defines the support for the transfer admittance. You can select it using the 2D Fluid Elements to Create Transfer Admittance On command (for surface of 2D fluid elements) or by referring to an existing group that contains surface of 2D fluid elements.Note: The Simcenter 3D Acoustics BEM solver environment supports only 2D fluid elements.
Group Reference	Lets you select the groups of free surface of 2D fluid elements to apply transfer admittance.For more information, see Group Reference options.
Select Object	Lets you select the geometry or FE entities on which to apply the transfer admittance 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.
Input Method
Method	Admittance and Source Coefficients — The transfer relation admittance defines a relationship between the acoustic velocities and pressures on one side of a surface, and the acoustic velocities and the pressures on the other side.The formulation matrix equation that links pressures with velocities is given by:where:, , , and = Admittance coefficients, = Source coefficients = Inlet velocity = Outlet velocity = Inlet pressure = Outlet pressureNote: = - Rigid Transfer Admittance — You can specifyA constant complex excitation with real and imaginary parts.A constant complex excitation with magnitude and phase angle.A frequency dependent field for the complex values.The rigid transfer admittance formulation is given by:where: = Admittance value = Correction factor = Inlet velocity = Outlet velocity = Inlet pressure = Outlet pressureGeometric Parameters — Mechel’s formula is used to calculate the admittance value. The dynamic viscosity and mass density use the default parameters corresponding to air at 250C.The geometric parameters are given by:Plate representation with dimensionswhere:2a = Diameter of perforations = Distance between axes = Plate thickness = Dynamic viscosity = Mass density = Correction factorYou can compute the impedance using Mechel’s formula.The above formula is evaluated for each forcing frequency, f.You can compute the admittance by inversing the impedance.Transfer Matrix — The transfer matrix formulation is given by:where: = Inlet velocity = Outlet velocity = Inlet pressure = Outlet pressureYou can define the following transfer matrix parameters: — Unitless — Unit is pressure per velocity — Unit is velocity per pressure — UnitlessYou can compute the alpha values from the transfer matrix using the equations:For more information, see Defining acoustic boundary conditions and simulation objects (Acoustics BEM).
Coefficients
Available when Method is set to Admittance and Source Coefficients.
Alpha Parameters	Specifies the transfer admittance coefficients and source coefficients.Create Modeling Object — Opens the Transfer Admittance - Coefficients dialog box, which lets you specify transfer admittance coefficients (, , , and ) and internal source coefficients ( and ).
Beta
Available when Method is set to Rigid Transfer Admittance.
Format	Specifies how the transfer admittance relationship is defined.
Real	Available when Format is set to Real/ Imaginary.Sets the real component values of the transfer admittance relation.
Imaginary	Available when Format is set to Real/ Imaginary.Sets the imaginary component values of the transfer admittance relation.
Magnitude	Available when Format is set to Magnitude/Phase.Sets the magnitude values of the transfer admittance relation.
Phase	Available when Format is set to Magnitude/Phase.Sets the phase angle values of the transfer admittance relation.
Specify Field	Available when Format is set to Field.Specifies the frequency dependent complex field values.Options include:Select Existing Field from List opens the Fields dialog box, where you can select a field.A field can define a magnitude that varies with independent variables such as frequency, temperature, or time. For more information about fields, see Fields.Formula Constructor opens the Formula Field dialog box, where you can define a formula to construct a field.For more information, see Define a boundary condition using a formula field.Table Constructor opens the Table Field dialog box, where you can define tabular data to construct a field.For more information, see Define a boundary condition using a table field and Define a material property using a table field.Plot (XY) plots the field as an XY graph.For more information, see Graph overview.Overlay (XY) overlays a plot on an existing plot. You can overlay up to 50 plots.For more information, see Overlay plots.Scale Factor — Sets the scaling of values present in the Field.
Sheet Parameters
Available when Method is set to Geometric Parameters.
Perforation Pattern	Specifies a hexagonal grid or square grid pattern of holes in the plate.Hexagonal Grid:Following are the perforation patterns for hexagonal grid:Hexagonal Grid****Square Grid:Following are the perforation patterns for square grid:Square Grid
Plate Thickness (I)	Specifies the thickness (l) of the plate.
Diameter of Perforations (2a)	Specifies the diameter of the perforations (2a).
Distance Between Axis (d)	Specifies the distance between the two axes (d).
Computation Parameters
Available when Method is set to Geometric Parameters.
Dynamic Viscosity	Specifies the dynamic viscosity () value of the transfer admittance.
Mass Density	Specifies the mass density () value of the transfer admittance.
Transfer Matrix
Available when Method is set to Transfer Matrix.
Parameters	Specifies acoustic transfer matrix coefficients.Create Modeling Object — Opens the Acoustic Transfer Matrix dialog box, which lets you specify acoustic transfer matrix coefficients (, , , ).

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Transfer Admittance dialog box (Acoustics Transient BEM), Simcenter 3D 2021.1 Series

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