Building MNF for Fluid-Structure Interaction Recovery
For Adams Durability to process acoustic pressures on flexible bodies, coustic mode shapes need to be present in the modal neutral file (MNF) of the flexible body. This is dones by having MSC Nastran recover a fluid mode for every mode shape computed from Component Mode Synthesis (CMS).
This is supported by the ADAMSMNF command along with the METHOD(COUPLED) or METHOD(SYMCOUP) command in Nastran's Case Control section. Refer to the MSC Nastran Quick Reference Guide and Reference Manual for information on how to use it.
MSC Nastran Fluid-Structure Interaction
MSC Nastran analyzes the dynamics of compressible fluids contained within arbitrarily shaped structures with the coupled fluid-structure method. It’s modeled as a three-dimensional fluid with conventional solid elements using acoustic property and material data and the fluid is automatically connected to the structure via the geometry. For FSI recovery on flexible bodies, the ACSETID option in the ADAMSMNF statement in case control section is required to select the acoustic grids to export the acoustic modes to be recovered in Adams Durability:
■ADAMSMNF FLEXBODY = YES ACSETID = n
where, n selects a set of acoustic grids to export the acoustic modes in MNF.
And the next statements in case control section are required to select the method to analyze FSI model:
■METHOD(COUPLED) = n
or
■METHOD(SYMCOUP) = n
where,
COUPLED | The referenced EIGR or EIGRL Bulk Data entry is applied to the structural and fluid coupled system of the model using subspace iteration method. |
SYMCOUP | The referenced EIGR or EIGRL Bulk Data entry is applied to the structural and fluid symmetrically coupled system of the model using Lanczos Method. |
n | Identification number of an EIGR or EIGRL Bulk Data entry. |