Random Results scenario (Simcenter Nastran FEM acoustics and Simcenter 3D Acoustics BEM)

The Random Results scenario is available for the following solution steps in the following solutions:

• Subcase - Random and Subcase - Random Distributed Acoustic Plane Waves for Nastran SOL 108 Direct Frequency Response and SOL 111 Modal Frequency Response

• Subcase Random Distributed Acoustic Plane Waves for Simcenter 3D Acoustics BEM

The Random Results scenario visualizes the following results. These scenario-based plots are available in random analyses only.

• XY plot (SORT2) for the Cross PSD functions, Auto PSD functions, and PSD functionsThe Cross PSD function gives the power shared by a given frequency for the two signals using its squared module, and the phase shift between the two signals at that frequency using its argument. The computation of PSD is done directly by Fast Fourier Transform (FFT) or computing an autocorrelation function first and then transforming it to Fourier Transform.

• 3D post view (SORT1) for the PSD Contours and RMS-Overall definitions3D post view visualization of RMS – Overall definition for Pressure RMS, Acceleration RMS, and Angular acceleration, and so on are displayed in vector format on the FE model.

To obtain Pressure, Acceleration PSD (Power Spectral Density), and CSD (Cross Power Spectral Density) XY plots, the corresponding output requests must be specified. It is available to require random samples in Distributed Acoustic Plane Waves Load.

The following XY plot displays the Pressure PSD results on fluid node ID 300473. The Pressure PSD is weak at around 16 Hz.

Power spectral density

The following XY plot displays the Acceleration X Pressure CSD result between first response (structural) node ID 80067 DOF X and second response (fluid) node ID 300849 DOF scalar. The maximum Acceleration X Pressure CSD result is at peak 87 Hz for the entire frequency range.

Cross power spectral density

The following figure displays the Overall Pressure RMS in a post view in SORT1 format.

Pressure RMS

Output definitions supported for Random results are Displacement PSD, Velocity PSD, Acceleration PSD, Pressure PSD (SORT1 or SORT2), and CSD result between all supported Random results (SORT2 only).

In Simcenter Nastran FEM in Subcase - Random Distributed Plane Waves, if you request SORT2 Acceleration and Pressure and a CSD result between them from output request, the following result output are supported by the Random Results scenario.

Definition	Visualization	Output
Cross PSD Function	XY Plot (SORT2)	Acceleration X Acceleration CSD****Acceleration X Pressure CSD
Auto PSD Function	Acceleration X Acceleration CSD
PSD Function	Pressure PSDAcceleration PSDAngular Acceleration PSD
RMS Overall	3D PostView (SORT1)	Pressure RMSAcceleration RMSAngular Acceleration RMS

In Simcenter Nastran FEM in Subcase - Random Distributed Plane Waves if you request SORT1 Acceleration and Pressure result from output request, following result output are supported by Random Results scenario.

Definition	Visualization	Output
PSD Contours	3D PostView (SORT1)	Pressure PSDAcceleration PSDAngular Acceleration PSD
RMS Overall	Pressure RMSAcceleration RMSAngular Acceleration RMS

For XY Plot (SORT2), you can switch between RMS and Peak result type formats or to display PSD and CSD results on octave bands. In the Scenario Based Data-Visualization Navigator, you can use the Convert from Cross PSD to Cross-Power check box, to convert from Cross PSD to Cross-Power.

In Simcenter Nastran, FEM for Random Subcase can be requested only one type result SORT1 or SORT2 at subcase level. If both types of random results SORT1 and SORT2 are needed, you should specify two Random subcases in the same Solution, one for SORT1 and one for SORT2.

In NX Acoustic BEM only one Subcase - Random Distributed Plane Waves is allowed per Solution and you can request both types of random results SORT1 and SORT2 in the same subcase.

Results Specific to Simcenter Nastran only.

Stress, Strain, SPC Force, Element Force are available in the CSD, PSD, and RMS formats.

Simcenter Nastran Von mises Stress (Per Ply) in Segalman and RMS SORT1 format are shown. Incident and Radiated Acoustic Power PSD and Transmission Loss results are available in SORT2 format.

Learn more

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Directivity Analysis scenario (Simcenter Nastran FEM acoustics and Acoustics BEM)

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Equivalent Radiated Power scenario

Function Plots scenario

Grid Contribution scenario (Simcenter Nastran and MSC Nastran )

Inverse Numerical Acoustics (L-Curve) scenario

Matrix Comparison Plots scenario (Simcenter 3D NVH)

Maximum Analysis Frequency scenario (Acoustics BEM)

Motion Results scenario (Simcenter 3D Motion)

Waterfall to Order-Cut scenario (Simcenter Nastran FEM acoustics and Acoustics BEM)

Peakout Frequencies Plots scenario

Plotting contribution from panels, structural modes, fluid modes, and MATVs

Quality Metrics scenario

Random VATV Forced Response Plots scenario

Ray Path Analysis scenario

Specialist Durability Function Definition scenario

Specialist Durability Plots scenario

Averaging scenario

Transmission Loss scenario (Simcenter Nastran FEM acoustics and Acoustics BEM)

Transfer Path Analysis (TPA) scenario (Simcenter Nastran FEM acoustics)

Force Transmissibility scenario (Simcenter Nastran FEM acoustics)

Point Mobility scenario (Simcenter 3D NVH)

Load Identification scenario (Simcenter Nastran FEM)

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Random Results scenario (Simcenter Nastran FEM acoustics and Simcenter 3D Acoustics BEM), Simcenter 3D 2021.1 Series

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