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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
5、Copyright 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 tha
6、t 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. T
7、wo 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 inp
9、ut 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 poi
10、nt 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_interpolati
11、on_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_
13、file_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
14、ACOUSTIC_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 PROJECTION_SURFACE PID 6 GAP_TOL 50.0 PLANE_TOL 0.1 SP
