Transfer Admittance dialog box (Simcenter Nastran)

Type
Type	Specifies the face pair creation method to use to define the two sides of the transfer admittance:Automatic Pairing Creation — Lets you create face pairs automatically by using the Create Automatic Face Pairs dialog box.Manual Pairing Selection — Lets you create face pairs manually by selecting a Source Region and a Target Region.
Name
Name	Sets the name of the transfer admittance.
Description	Sets a description for the transfer admittance.
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.
Automatic Face Pair Creation
Available when Type is set to Automatic Pairing Creation.
Face Pairs	Create Face Pairs — Opens the Create Automatic Face Pairs dialog box, which enables you to specify face pair generation properties, preview face pairs, and generate face pairs automatically.
Regions
Available when Type is set to Manual Pairing Selection.
Source Region	Lets you select the Region that defines the contacting surface in the transfer admittance pair.This source face defines the direction for the transfer admittance regions that get created.Select an existing region or click Create Region to create a new region, select the acoustic fluid element faces from the acoustic model, or select an existing group of acoustic fluid element faces by selecting the Group Reference check box in Region dialog box.For more information, see Group Reference options.Note: The source and the target regions must contain the same type of entity (that is, faces, element faces, and so on).
Target Region	Lets you select the Region that defines the contacting surface in the transfer admittance pair.Select an existing region or click Create Region to create a new region, select the acoustic fluid element faces from the acoustic model, or select an existing group of acoustic fluid element faces by selecting the Group Reference check box in Region dialog box.For more information, see Group Reference options.
Parameters
Search Distance	Specifies the search distance value for transfer admittance regions.For more information, see ACTRAD.
Advanced Options
Tolerance Angle	Specifies the maximum tolerance angle.The software uses this angle to determine whether the acoustic source and target region are overlapping.If the angle between the normal of the acoustic source and target region exceeds this value, they cannot be paired.For more information, see ACTRAD.
Input Method
Method	Admittance and Source Coefficients — Transfer admittance is linking the velocity values (v1, v2) and pressure values (p1, p2) on both sides of a surface or object.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 pressureRigid 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 complex field value.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 geometric parameters are given by:Plate representation with dimensionsWhere,2a = Diameter of perforations = Distance between axes = Plate thickness = Dynamic viscosity = Mass density = Correction factorThe dynamic viscosity and mass density use the default parameters corresponding to air at 250 C.You can compute the impedance by using Mechel’s formula.The above formula is evaluated for each forcing frequency, f.(Refer Sheet Parameters below for values.)You can compute the admittance (f) by inversing the impedance.Transfer Matrix — Transfer matrix is defined as 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.Its formulation is given as: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 — UnitlessFor more information, see Boundary conditions overview (FEM acoustics).
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 of the transfer admittance relation.
Imaginary	Available when Format is set to Real/ Imaginary.Sets the imaginary component of the transfer admittance relation.
Magnitude	Available when Format is set to Magnitude/Phase.Sets the magnitude of the transfer admittance relation.
Phase	Available when Format is set to Magnitude/Phase.Sets the phase angle 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.
Correction Factor (K)	Specifies correction factor value of the transfer admittance.
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 thickness (l) of the plate.
Diameter of Perforations (2a)	Specifies diameter of perforations (2a).
Distance Between Axis (d)	Specifies distance between two axes (d).
Computation Parameters
Available when Method is set to Geometric Parameters.
Dynamic Viscosity	Specifies dynamic viscosity () value of the transfer admittance.
Mass Density	Specifies mass density () value of the transfer admittance.
Correlation Factor (K)	Specifies correction factor 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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Boundary conditions overview (FEM acoustics)

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Acoustic Transfer Matrix dialog box

Transfer Admittance - Coefficients dialog box

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Transfer Admittance dialog box (Simcenter Nastran), Simcenter 3D 2021.1 Series

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