Actran Analysis Submission, Frequency Domain
Acoustics → Frequency Domain → Actran Analysis Submission, Frequency Domain
Exports an .mdf (Modal Deformation File) file that is referenced in a NASTRAN analysis followed by an Actran acoustic analysis of the selected flexible component. All files created during this process are written in the same directory as the mnf file is located.
Common Setup
For the option: | Do the following: |
|---|---|
Flexible Body | A flexible body within the Adams model must be chosen; the vibrational results of this flexible body from an Adams simulation will be used as the basis for the acoustics analysis. |
Output File Prefix | Specifies the name of the files written to disk by the acoustics analysis |
Actran Analysis | Specifies the name of the acoustics analysis job |
MDF File Name | Specifies the name of the modal deformation file containing the participation factors |
Analysis | Select the Adams analysis whose results for the selected flexible body should be the basis of the acoustics simulation |
Output Time Start/End | Defines the start of the time range from the Adams analysis for which the acoustics analysis should be run |
Skip | Adams time steps can be skipped to reduce the computational time of the acoustics analysis. |
Advanced Setup | Opens the advanced setup tabs, available tabs are Mesh, Results Content, DFT, Environment, Far Field, and Analysis Setup. |
Export FE Data | selecting this directs Adams to copy the following files in the analysis directory: ■Structural mesh ■Modes in MNF format |
OK | Starts the acoustic simulation and closes the dialog |
Apply | Starts the acoustic simulation and keeps the dialog open |
Cancel | Closes the dialog |
Advanced Setup
Mesh Tab
The Mesh Tab allows creation of the acoustic mesh utilized for the acoustic radiation of the vibrating structure. The inputs are described below. See the Mesh section of the Appendix for more details.
Mesh | Create or use the mesh files for Actran Analysis |
|---|---|
Mesh Type | Select the mesh type dependent on your needs. ■Mesh already provided: Choose this option if the acoustic mesh is already created and available. ■Automatic Mesh: This option can be chosen to automatically generate the acoustic mesh. In most of the cases mesh creating will be successful. In case that the Automatic mesh is not successful, one should manually create the shrinkwrap mesh and supply that here. |
Mesh File | Browse for and specify the mesh file if either "Mesh already provided" or "Automatic Mesh" are chosen for Mesh Type. |
Elements per Wavelength | Defines how many elements will be generated per minimal wavelength. The minimal wavelength is defined by the Maximum Frequency. The process is using quadratic mesh. Default value: 4 |
Distance from Structure | Defines the distance of the shrinkwrap to the structure. 0.0 to 1 cm are good choices depending on the size and complexity of the structure. Default value is 0.0 |
Fill hole size (% of structure size) | Defines which holes will be filled by the automatic mesh generation algorithm. Please note that if all holes are not filled, the shrinkwrap might enter inside the structure. This should be absolutely avoided. See Edit button for checking the shrinkwrap. |
Select | This button opens an additional dialog box (see below) to select acoustic mesh files individually. Dialog to select the acoustic mesh files individually, for: ■Header dat file ■Shrinkwrap Mesh |
Create | This button will create the acoustic mesh if the "Mesh already provided" or “Automatic Mesh” options are chosen for Mesh Type. |
Show | This button displays the acoustic mesh in Adams View. |
Edit | This Button opens the shrinkwrap mesh in Actran VI. Please note that for mesh modifications, an Actran VI license is necessary, the "Actran Entry for Adams" license is not sufficient for this option. |
Status | This button displays the current status of the meshes in the info window. Note: Actran Frequency Domain analysis cannot be submitted if no mesh is available for the analysis. |
Results Content Tab
In the results content tab, the post-processing content is defined.
Results Content | |
|---|---|
Output Format | Defines the output format of the results. Images, ascii-format and both can be chosen. |
SPL over time at microphone(s) | Creates the Sound Pressure Level (SPL) per time period in a time dependent plot. |
SPL output in dBA | Applies the A weighting function to acoustic results expressed in dB. |
Analysis parameters Tab
The Discrete Fourier Transformation (DFT) tab contains the properties for the transformation of time domain signals into frequency domain results. The inputs are described below. See the Discrete Fourier Transform (DFT) section of the Appendix for more details.
DFT | Discrete Fourier Transformation |
|---|---|
Time Windowing | Defines the form of the window. While Rectangular windows will apply a constant factor of 1 (thus no window) to the sampled time signal, other window types will apply factors from [0,1] to the sampled time signal. Options are Triangular, Hamming, Hanning, Blackman and Blackman Harris. For example, the Hanning windowing is defined by the formula with n the number or the  sample points, M the quantity of sample points in the window and w the window function |
Time Interval | Defines the length of each time interval where the DFT is applied |
Overlap of Time Interval | Defines the percentage of the overlap of the subsequent time interval. |
Frequency range (Start/Step/End) | Defines the frequencies of the Frequency domain calculation: ■Start/Step: These frequencies define the first computed frequency and the frequency step. Default values are defined by the period of the time interval (see the Discrete Fourier Transform (DFT) section in the Appendix). ■End: This frequency defines the last frequency to be computed. Note that the time step length influences the maximal frequency that can be computed, through the Nyquist criterion. |
Number of Radiation frequencies for Green analysis | Defines the number of frequencies used for the first step (Radiation) of the Green analysis. Default value is 4. More frequencies may be required for better accuracy when dealing with complex geometries. |
Number of bands for adaptive volume mesh | Defines the number of frequency ranges used for the adaptive mesh. Default value: 6 |
Use Hexa mesh | Activates the usage of hexahedral elements in the volume mesh. If the volume mesh generation fails, try de-activating this option. Default: activated. |
Relative thickness for adaptive PML | Defines the thickness of the PML for each frequency band. The value provided corresponds to the number of acoustic wavelengths at the lower limit of each frequency band. Default value: 1 |
Environment Tab
The Environment tab defines the properties of ambient fluid surrounding the structure.
Environment | |
|---|---|
Acoustic Environment | Allows to automatically define the properties of the Air at a given temperature. Following properties are influenced by the temperature defined. |
Speed of Sound | The speed of sound is the distance travelled per unit of time by a sound wave propagating through an elastic medium (m/sec) |
Fluid Density | The mass of the fluid per unit volume (kg/m*3) |
Far Field Tab
The Far Field Tab defines the position of the microphones and the properties of the infinite elements. The inputs are described below. See the Far Field section of the Appendix for more details.
Far Field | |
|---|---|
Order of Infinite Elements | Defines the number of interpolation points for each infinite element, which is used to model nonreflecting boundary conditions and the acoustic radiation outside of the finite element mesh. Default value is 10. |
Microphone Table File | Defines the position of the microphones; the default position is based on the ISO3744 and can be found in the installation folder "<top_dir>\acoustics\examples\ISO3744_meter.mic" |
Translation Center of Microphones | Defines the center location of the microphones. Default value: center of gravity of the flexible body. |
Scale Factor Microphones | Scales the coordinates of the microphone positions. |
Microphone for post | Select the microphones used for additional post-processing output; the button "All" will select all microphones. |
Show Microphones | This button is enabled after the acoustic mesh is generated and displays all the microphones available as yellow or red spheres (the red ones indicate microphones selected for extra post-processing results). |
Overwrite defaultss | Radius of Infinite Elements, Center of Infinite Elements and Scale Factor for Microphones all have automatic defaults. This "Overwrite defaults" button allows users to change those inputs. For instance the, user can change the distance of the microphones from structure by modifying the scaling factor for microphones. |
Analysis Setup Tab
In the Analysis Setup tab, the following parameters are defined. See the Analysis set-up section of the Appendix for more details.
Analysis Setup | |
|---|---|
Gap Tolerance | Defines the tolerance parameter to couple the shrinkwrap with the structural acoustic surfaces. Default value is twice the distance specified in Mesh tab, which can be used in other cases as well. If distance is 0.0, Gap Tolerance is set to 0.01 m. |
Output Map | Allows the user to create an acoustic 3D map in time domain. Please note that to open the map in Actran VI the license for Actran VI is needed, the "Actran Entry for Adams" license is not sufficient. Note that asking for maps may increase computational time significantly. Default value is 'No'. |
Output Map Steps | Specifies the time steps of the output map. Please note that an output map can demand a lot of hard drive space thus removing steps from the output could be important. Maps are output at each time step for value=1, every two steps for value=2 and so on. |
Memory | Memory dedicated to the calculation. Quantity depends on the size of the acoustic mesh. Unit is MB. |
Acoustics, What Happens?
1. In the field Flexible Body it is checked if every input is there and valid Prerequisites are: MASTER, DABALL and IFPDAT from previous SOL103 solution
2. The modal coordinates are exported
3. Session file for Actran is written to setup the Actran model
4. Import file for Adams to import Actran results is written
5. Batch file is written to execute Actran run