1、Copyright Free Field Technologies WS 9 - Acoustic Radiation with RADACT ACTRAN Training: ACOUSTICS 2 Copyright Free Field Technologies Content Introduction RADACT- Direct frequency response Building RADACT input file Pre-processing Computation Post-processing RADACT- Green analysis Editing RADACT in
2、put file Pre-processing Computation Post-processing Going further 3 Copyright Free Field Technologies Introduction Pre-requisites - before going through this presentation, the reader should have read and understood the following presentations: Theory Acoustic Simulations Theory Acoustic BC MESH The
3、objectives of this workshop are the following: Explain how to use Actran RADACT in order to generate, compute and post-process the acoustic radiation of a pre-computed vibrating structure The Actran models generated through RADACT in this workshop correspond to a Direct frequency analysis (part 1) a
4、nd a Green analysis (part 2) of a free field acoustic radiation problem using IFE approach and BC_MESH feature. 4 Copyright Free Field Technologies Modeling Process Acoustic Mesh (BDF format) NASTRAN Mesh and Nastran Results RADACT Input File Automatic Run and Post-Processing FRFs Maps Waterfall 5 C
5、opyright Free Field Technologies Workshop Description The vibration of the following gearbox has been computed using NASTRAN The vibration are available from 10Hz to 2010Hz with a step of 100Hz in the OP2 format The objective is to study the noise radiated by this gearbox in free field assuming that
6、 the excitation and radiation processes are weakly coupled Displacement at 510Hz 6 Copyright Free Field Technologies Structure The NASTRAN result file (structure.op2) contains the displacement of the gearbox from 10Hz to 2010Hz, step of 100Hz. 3 subcases: 2,3 and 4 are available in this OP2 file. Tw
7、o surfaces : PID 16 and PID 17 radiate the acoustic energy in free field. PID 17 PID 16 7 Copyright Free Field Technologies Acoustic mesh Acoustic mesh (fluid.bdf) consists of: One 3D element set to model the acoustic mesh(blue) One 2D element set to model the coupling surface(brown) One 2D element
8、set to model the infinite elements(yellow) Acoustic mesh 3D element set (id 1) Infinite elements 2D Element set (id 6) Coupling surface 2D Element set (id 2) Copyright Free Field Technologies Part 1: Direct Frequency Response Building RADACT input file 9 Copyright Free Field Technologies RADACT inpu
9、t file overview Open the input.dat file in the model_direct folder This RADACT model includes 4 data blocks: ACOUSTIC_MODEL_IMPORT STRUCTURE_MODEL_IMPORT RUN_ACTRAN The FIELD_POINT Editing this input file see the next slides BEGIN FIELD_POINT field_point_id number of field points for each field poin
10、t field point external number,. x, y and z point coordinates end for END FIELD_POINT field_point_id BEGIN ACOUSTIC_MODEL_IMPORT BEGIN FINITE_DOMAIN NASTRAN mesh_file_name PID list_of_pid SOUND_SPEED c FLUID_DENSITY rho END FINITE_DOMAIN BEGIN INFINITE_DOMAIN PID list_of_pid ORDER radial_interpolatio
11、n_order COORDINATE_SYSTEM coordinates of the local system origin for each dimension (3) components of the related local axis end for END INFINITE_DOMAIN BEGIN PROJECTION_SURFACE PID list_of_pid GAP_TOL extrude_tolerance PLANE_TOL relative_tolerance SPLITTING_METHOD NO or AUTO END PROJECTION_SURFACE
12、END ACOUSTIC_MODEL_IMPORT BEGIN RADACT BEGIN RUN_ACTRAN FREQUENCY_LIST list_of_frequencies FREQUENCY_RANGE fstart fstep fend GREEN_ANALYSIS 0 or 1 PANEL_CONTRIBUTION 0 or 1 MODE_CONTRIBUTION 0 or 1 SOLVER MUMPS PLT_FILE plt_result_file_name MAP_FILE NFF map_result_dir_name FIELD_MAP_FILE fieldmesh_f
13、ile_name NFF fieldmap_dir_name END RUN_ACTRAN BEGIN STRUCTURE_MODEL_IMPORT NASTRAN mesh_file_name NASTRAN_BC_FILE result_file_name NASTRAN_MODAL_PARTICIPATION modal_part_file PID list_of_pid LOADCASE list_of_subcases or ALL END STRUCTURE_MODEL_IMPORT END RADACT 10 Copyright Free Field Technologies A
14、COUSTIC_MODEL_IMPORT BEGIN ACOUSTIC_MODEL_IMPORT BEGIN FINITE_DOMAIN NASTRAN /fluid/fluid.bdf PID 1 SOUND_SPEED 340000 FLUID_DENSITY 1.225e-012 END FINITE_DOMAIN BEGIN INFINITE_DOMAIN PID 2 ORDER 10 COORDINATE_SYSTEM 0. 0. 0. 1000.0 0.0 0.0 0.0 1000.0 0.0 0.0 0.0 1000.0 END INFINITE_DOMAIN BEGIN PRO
15、JECTION_SURFACE PID 6 GAP_TOL 50.0 PLANE_TOL 0.1 SPLITTING_METHOD AUTO END PROJECTION_SURFACE END ACOUSTIC_MODEL_IMPORT Acoustic model contains: FINITE_DOMAIN: Mesh file: fluid.bdf Acoustic domain assigned to 3D domain PID 1 Fluid material: air (in ton/mm unit) INFINITE_DOMAIN: Assigned to 2D domain
16、 PID 2 IFE order:10 IFE center: x=0, y=0, z=0 IFE coordinates: global coordinates PROJECTION_SURFACE: Coupling surface: 2D domain PID 6 Projection tolerance: GAP_TOL 50 and PLANE_TOL 0.1 PLITTING_METHOD: AUTO automatically dividing the coupling surface into different partitions according to the proj
17、ection of the different structure PIDs on the acoustic surface PID 6. 11 Copyright Free Field Technologies STRUCTURE_MODEL_IMPORT STRUCTURE_MODEL_IMPORT data block: Structure mesh file: structure.bdf Structure vibration result file: structure.op2 Displacement are provided directly in physical coordi
18、nates for each frequency NASTRAN_MODEL_PARTICIPATION must be removed PID 16 17: only PID 16 and 17 in the structure mesh file are assumed to radiate acoustic energy in free field. Two subcases 2 and 3 are selected in this analysis (there are 3 subcases 2,3 and 4 in op2 file) BEGIN STRUCTURE_MODEL_IM
19、PORT NASTRAN /structure/structure.bdf NASTRAN_BC_FILE /structure/structure.op2 LOADCASE 2 3 PID 16 17 END STRUCTURE_MODEL_IMPORT PID 17 PID 16 12 Copyright Free Field Technologies RUN_ACTRAN RUN_ACTRAN specify the analysis parameters and the outputs: Performed frequencies: from 10Hz to 2010 Hz with
20、step of 100Hz Direct Frequency Response: Set GREEN_ANALYSIS to 0 Set MODE_CONTRUBUTION to 0 To access to the contribution of each structure PID in Post-Processing: set PANEL_CONTRIBUTION to 1 Solver: Mumps Output FRF: results computed at the field points defined in field_points.dat file are stored i
21、n res_direct.plt Output Map: store the results computed on the computational mesh in NFF database maps_direct.nff Field Map: the results computed on the field mesh field_mesh.bdf and stored in field_mesh.nff BEGIN RUN_ACTRAN FREQUENCY_RANGE 10.0 100 2010 GREEN_ANALYSIS 0 PANEL_CONTRIBUTION 1 MODE_CO
22、NTRIBUTION 0 SOLVER MUMPS PLT_FILE res_direct.plt MAP_FILE NFF maps_direct.nff FIELD_MAP_FILE field_mesh.bdf NFF field_mesh.nff END RUN_ACTRAN INCLUDE_FILE field_points.dat 13 Copyright Free Field Technologies RADACT input file Verify the RADACT input file and save it as input_direct.dat: INCLUDE_FI
23、LE field_points.dat BEGIN ACOUSTIC_MODEL_IMPORT BEGIN FINITE_DOMAIN NASTRAN /fluid/fluid.bdf PID 1 SOUND_SPEED 340000 FLUID_DENSITY 1.225e-012 END FINITE_DOMAIN BEGIN INFINITE_DOMAIN PID 2 ORDER 10 COORDINATE_SYSTEM 0. 0. 0. 1000.0 0.0 0.0 0.0 1000.0 0.0 0.0 0.0 1000.0 END INFINITE_DOMAIN BEGIN PROJ
24、ECTION_SURFACE PID 6 GAP_TOL 50.0 PLANE_TOL 0.1 SPLITTING_METHOD AUTO END PROJECTION_SURFACE END ACOUSTIC_MODEL_IMPORT BEGIN RADACT BEGIN RUN_ACTRAN FREQUENCY_RANGE 10.0 100 2010 GREEN_ANALYSIS 0 PANEL_CONTRIBUTION 1 MODE_CONTRIBUTION 0 SOLVER MUMPS PLT_FILE res_direct.plt MAP_FILE NFF maps_direct.n
25、ff FIELD_MAP_FILE field_mesh.bdf NFF field_mesh.nff END RUN_ACTRAN BEGIN STRUCTURE_MODEL_IMPORT NASTRAN /structure/structure.bdf NASTRAN_BC_FILE /structure/structure.op2 LOADCASE 2 3 PID 16 17 END STRUCTURE_MODEL_IMPORT END RADACT Copyright Free Field Technologies Part 1: Direct Frequency Response P
26、re-processing 15 Copyright Free Field Technologies Generating Actran input file During the pre-process step, RADACT generates the standard ACTRAN input file according to the various parameters set-up in the RADACT input file. Launching the command line : Actran input file input_direct_radact.dat is
27、created by RADACT in this step. actranpy u RADACT i input_direct.dat m 1000 e PREPROCESS 16 Copyright Free Field Technologies Visualizing the analysis model in Actran VI Open input_direct_radact.dat in Actran VI Check if the analysis tree is identical to the one shown 17 Copyright Free Field Technol
28、ogies RADACT Keyword Effect on Analysis Model PANEL_CONTRIBUTION 1 6 loadcases are generated Loadcase 1, 2 correspond to Nastran subcases 2 and 3 where the contribution of both PID 16 + PID 17 are considered. Loadcase 3,4: only PID 16 contributes to the acoustic radiation Loadcase 5,6: only PID 17 c
29、ontributes to the acoustic radiation Setting PANEL_CONTRIBUTION 1+SPLITTING_METHOD AUTO, the coupling surface is automatically spitted into 2 by Actran (coupling surface 1 and 2) corresponding to 2 structure PIDs 16 and 17. PID 17 PID 16 Copyright Free Field Technologies Part 1: Direct Frequency Res
30、ponse Computation 19 Copyright Free Field Technologies Running Actran computation An ACTRAN run can then be launched through RADACT with the following command: Log file of the Actran computation is located inside the local_report directory actranpy u RADACT i input_direct.dat m 1000 e RUN_ACTRAN Cop
31、yright Free Field Technologies Part 1: Direct Frequency Response Post-processing 21 Copyright Free Field Technologies POST_WATERFALL (1) POST_WATERFALL allows the plot of waterfall diagrams in WATERFALLViewer. The sound pressure level following the microphone ids (directivity) and the frequencies ca
32、n be easily accessed. Running POST_WATERFALL command: actranpy u RADACT i input_direct.dat e POST_WATERFALL 22 Copyright Free Field Technologies POST_WATERFALL (2) Choose a loadcase in RADACT result selector window Subcase 2, all panel Drag the vertical line to the desired frequency (1110Hz) at whic
33、h directivity is plotted and the horizontal line to the field point id (50) where FRF is plotted. 23 Copyright Free Field Technologies POST_WATERFALL (3) Subcase 2, panel 16 24 Copyright Free Field Technologies POST_WATERFALL (4) Subcase 2, panel 17 25 Copyright Free Field Technologies Running POST_
34、VI POST_VI allows the plot of color maps in Actran VI Launching POST_VI: actranpy u RADACT i input_direct.dat e POST_VI 26 Copyright Free Field Technologies POST_VI: panel contribution Choose a loadcase, frequency and operator in RADACT result selector window Plot dB pressure at 1110Hz, Subcase 2 PI
35、D 16 PID 17 all panel 27 Copyright Free Field Technologies POST_VI: panel contribution Plot Real part of pressure at 1110Hz, Subcase 2 Beside RADACT result selector, the maps properties can also be normally modified as for a standard model. PID 16 PID 17 all panel Copyright Free Field Technologies P
36、art 2: Green analysis 29 Copyright Free Field Technologies Pre-processing: Editting RADACT input file In this part, a new model using Green analysis sequence is created based on the one created in part 1 Since the input structure and the cavity mesh remain the same, only RUN_ACTRAN data block is mod
37、ified Green analysis will be used in this model Set GREEN_ANALYSIS to 1 Comment the FIELD_MAP_FILE command Rename the *plt file and the maps file. Remark: In Green analysis, the contribution to the computed noise level of each element of the structure can be displayed using the output map (MAP_FILE)
38、. The computation of the pressure field on a field mesh is not advised when using Green analysis. This would require the computation of the solution with as many right hand sides (excitation vectors) as points in the field mesh BEGIN RUN_ACTRAN FREQUENCY_RANGE 10.0 100 2010 GREEN_ANALYSIS 1 PANEL_CO
39、NTRIBUTION 1 MODE_CONTRIBUTION 0 SOLVER MUMPS PLT_FILE res_green.plt MAP_FILE NFF maps_green.nff / FIELD_MAP_FILE field_mesh.bdf NFF field_mesh.nff END RUN_ACTRAN INCLUDE_FILE field_points.dat 30 Copyright Free Field Technologies Pre-processing: Verifying RADACT input file Save the RADACT input file
40、 as input_green.dat and verify if it is correct as the following: INCLUDE_FILE field_points.dat BEGIN ACOUSTIC_MODEL_IMPORT BEGIN FINITE_DOMAIN NASTRAN /fluid/fluid.bdf PID 1 SOUND_SPEED 340000 FLUID_DENSITY 1.225e-012 END FINITE_DOMAIN BEGIN INFINITE_DOMAIN PID 2 ORDER 10 COORDINATE_SYSTEM 0. 0. 0.
41、 1000.0 0.0 0.0 0.0 1000.0 0.0 0.0 0.0 1000.0 END INFINITE_DOMAIN BEGIN PROJECTION_SURFACE PID 6 GAP_TOL 50.0 PLANE_TOL 0.1 SPLITTING_METHOD AUTO END PROJECTION_SURFACE END ACOUSTIC_MODEL_IMPORT BEGIN RADACT BEGIN RUN_ACTRAN FREQUENCY_RANGE 10.0 100 2010 GREEN_ANALYSIS 1 PANEL_CONTRIBUTION 1 MODE_CONTRIBUTION 0 SOLVER MUMPS PLT_FILE res_green.plt MAP_FILE NFF maps_green.nff END RUN_ACTRAN BEGIN STRUCTURE_MODEL_IMPORT NASTRAN /structure/structure.bdf NASTRAN_BC_FILE /structure/structure.op2 LOADCASE 2 3 PID 16 17 END STRUCTURE_MODEL_IMPORT END RADACT
