How to retrieve nodal acceleration for all frequencies of different RPM sets in Harmonic Analysis us

Ayush Kumar
Ayush Kumar Member, Moderator, Employee Posts: 389
First Anniversary Ansys Employee Solution Developer Community of Practice Member First Answer
edited June 2023 in Structures

While trying to retrieve nodal acceleration for all frequencies of different RPM sets in Harmonic Analysis using DPF operator "AX", I get the following error:

enter image description here

Tagged:

Answers

  • Ayush Kumar
    Ayush Kumar Member, Moderator, Employee Posts: 389
    First Anniversary Ansys Employee Solution Developer Community of Practice Member First Answer
    Answer ✓

    This is a bug in 2021R1 (DPF). The workaround to this is using the displacement operator UX and do a double derivative of UX to get acceleration using cplx_derive operator.

    I have this example code which retrieves Nodal acceleration for a defined Named selection "node" (containing 1 node) in Mechanical and prints out the acceleration amplitude for that node in X for each frequency and rpm set in a Harmonic Analysis.

    Assumption: Each RPM set has same number of solution intervals. In case of different solution intervals, please adjust the code to get the correct rpm set number.

    enter image description here

    import math
    import mech_dpf
    mech_dpf.setExtAPI(ExtAPI)
    import Ans.DataProcessing as dpf
    from collections import defaultdict
    
    # Data Source
    ds = mech_dpf.GetDataSources(0)  # Adjust analysis system index
    time_provider = dpf.operators.metadata.time_freq_provider()
    time_provider.inputs.data_sources.Connect(ds)
    
    # Number of frequencies
    freqs = time_provider.outputs.time_freq_support.GetData()
    numSets = freqs.NumberSets
    ids = [index + 1 for index in range(numSets)]
    
    # Get number of RPMs
    analysis = Model.Analyses[0].AnalysisSettings  # Adjust analysis system index
    n_rpms = analysis.NumberOfRPMs
    n_freqs_per_rpm = int(len(ids) / n_rpms)
    
    node_scoping = dpf.data.Scoping()
    node_scoping.Ids = ExtAPI.DataModel.GetObjectsByName("node")[0].Ids
    
    freq_scoping = dpf.data.Scoping()
    freq_scoping.Ids = ids
    
    # Displacement X
    u_x = dpf.Operator("UX")
    u_x.Connect(0, freq_scoping)
    u_x.Connect(1, node_scoping)
    u_x.Connect(4, ds)
    
    # Velocity X - Single Derivative
    u_d_x = dpf.Operator("cplx_derive")
    u_d_x.Connect(0, u_x)
    
    # Acceleration X - Double Derivative
    u_d2_x = dpf.Operator("cplx_derive")
    u_d2_x.Connect(0, u_d_x)
    
    for freq_index in ids:
        real =  u_d2_x.GetOutputAsFieldsContainer(0).GetFieldByTimeId(freq_index).Data[0]
        imaginary = u_d2_x.GetOutputAsFieldsContainer(0).GetImaginaryField(freq_index).Data[0]
    
        amplitude = (real ** 2 + imaginary ** 2) ** 0.5
    
        rpm_set = math.ceil(freq_index / float(n_freqs_per_rpm))
        print "RPM Set - %s, Frequency - %s, Accleration X - %s" % (rpm_set, freq_index, amplitude)
    
  • Adriano Zaffora
    Adriano Zaffora Member, Employee Posts: 20
    Ansys Employee Solution Developer Community of Practice Member First Comment

    ACEL is not in the RST for harmonic response. You can calculate it by scaling displacement by (2pi()FREQ)^2