Fluid-Structure Interface Modeling Parameters dialog box (Acoustics BEM)

Modeling Object
Name	Sets the name of the modeling object.
Label	Sets a unique numerical identifier for the modeling object.
Properties
View as Model Formulation	Lets you select the BEM solver formulation method as:Standard IBEMFast MultipoleH-MatrixFor more information see Solution formulation methods for indirect acoustic analysis (Acoustics BEM).
Description	Lets you specify a description for this modeling object. Enter a brief description or click to open a text editor, where you can enter a longer description.
Type of Coupling	Specifies the type of coupling for the Standard IBEM solver.**Two-way Coupling (STRONG)**Transfers the effect of structural vibration to the fluid, and then transfers the resulting acoustic pressure loads to the structure.**Effect of Structure on Fluid Only (WEAK)**Transfers the effect of structural vibration to the fluid only, and ignores the effect of the fluid pressure on the structure.Specifies the type of coupling for the Fast Multipole and H-Matrix solvers.**Effect of Structure on Fluid Only (WEAK)**Transfers the effect of structural vibration to the fluid only, and ignores the effect of the fluid pressure on the structure.
Search Units	Specifies the search unit to define which elements are to be coupled.AbsoluteUses a normal line in each integration point of the structural element; the closest acoustic element within a certain distance is searched for the outward and inward specified distances.RelativeUses relative model units based on the entire structural model, and uses a scaled distances (for example, 0.2 or 0.3 times) of the entire structural model to search for acoustic elements.If no acoustic element is found within the tolerance, the elements are not coupled. If a second acoustic element on the same side is found within that tolerance, only the closest one is coupled. If the structural mesh is to be coupled on both sides, the procedure is repeated for the other side of the structural mesh. The tolerance should be large enough to couple all structural elements with the acoustic mesh, but small enough to avoid coupling structural elements that are not directly exposed to the fluid (for example, a case with a double-walled structure where the outside wall is not acoustically coupled to a cavity inside).The acoustic element center is considered to determine which fluid element is affected by the one-way coupling. To avoid coupling instabilities, use a search distance greater than one-half of the element size for both Relative and Absolute selections.
Outward Normal Search Distance	Specifies the distance to search in the outward normal direction to detect the fluid-structure interface.
Inward Normal Search Distance	Specifies the distance to search in the inward normal direction to detect the fluid-structure interface.
Angular Tolerance	Specifies the angular tolerance for the Standard IBEM solver. Not available for Fast Multipole or H-Matrix solutions.Searches the fluid elements which normal are within the specified tolerance. For example, if the tolerance is set to 60 degrees, the fluid elements in between 0 and 60 degrees are searched.Determines whether a fluid free face and a structural face will be coupled.The combined effect of the search distances and the angular tolerance will find the desired acoustic elements.Note: The software takes the absolute value of the angle between the normal of the structure and the fluid face. Therefore, the Angular Tolerance value must be between 0 and 90.
Fluid Interface
Fluid Element Side	Specifies the fluid elements to define the fluid part of the fluid-structural interface. You can specify the side of the acoustic mesh to which the structural vibration is transferred.Top and Bottom — Transfers the vibration to the top and bottom side of the acoustic mesh.
Fluid Elements for the Interface	Specifies the fluid elements to include in the interface.All — Includes all the fluid elements for the fluid interface.Specify Included Elements — Includes a group of fluid elements for the fluid interface that you select from the fluid mesh or that you select by group reference.
Structural Interface
Structural Elements for the Interface	Specifies the structural elements or the structural entities to include in the interface.All Structural 2D Elements — Includes all the structural 2D shell elements for the structural interface.Specify Included 2D Elements or 3D Element Faces — Includes a group of structural 2D shell elements or a group of structural 3D element faces for the interface that you select from the structural mesh or that you select by group reference.

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Fluid-Structure Interface Modeling Parameters dialog box (Acoustics BEM), Simcenter 3D 2021.1 Series

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