.flt file

An OptiStruct ASCII format results file containing the summary of aeroelastic flutter analysis.

File Creation

This file is created by default for aeroelastic flutter analysis.

File Contents

A typical .flt file containing the flutter summary is:
 Subcase =        1
                                                          FLUTTER  SUMMARY
                          CONFIGURATION = AEROSG2D     XY-SYMMETRY = ASYMMETRIC     XZ-SYMMETRY =  SYMMETRIC
       POINT =        1 MACH NUMBER =  0.9000    DENSITY RATIO =  1.0000E-01     METHOD = K   
        KFREQ            1./KFREQ         VELOCITY            DAMPING         FREQUENCY            COMPLEX   EIGENVALUE
        0.0010       1.0000000E+03     UNSTABL-SYSTEM    UNSTABL-SYSTEM    UNSTABL-SYSTEM    4.3931949E+04     2.0325712E+02
        0.0010       1.0000000E+03     STABLE-SYSTEM-    STABLE-SYSTEM-    STABLE-SYSTEM-    2.0193361E+04    -1.1860746E+02
        0.0010       1.0000000E+03     STABLE-SYSTEM-    STABLE-SYSTEM-    STABLE-SYSTEM-    3.0546665E+05    -7.2971381E+02
 *** USER INFORMATION MESSAGE
THE K OR KE METHOD OF FLUTTER ANALYSIS HAS FOUND A ROOT THAT HAS NO PHYSICAL INTERPRETATION.
        Subcase =        1
                                                          FLUTTER  SUMMARY
                          CONFIGURATION = AEROSG2D     XY-SYMMETRY = ASYMMETRIC     XZ-SYMMETRY =  SYMMETRIC
       POINT =        2 MACH NUMBER =  0.9000    DENSITY RATIO =  1.0000E-01     METHOD = K   
        KFREQ            1./KFREQ         VELOCITY            DAMPING         FREQUENCY            COMPLEX   EIGENVALUE
        0.1800       5.5555556E+00     4.1282076E+01    -5.0589764E-02     4.2403886E+00    -1.6998593E+03    -8.5995482E+01
        0.1800       5.5555556E+00     1.7230486E+02    -8.9340353E-02     1.7698711E+01    -2.9453872E+04    -2.6314194E+03
        0.1800       5.5555556E+00     4.4410222E+02    -5.0649869E-01     4.5617037E+01    -1.5696010E+05    -7.9500083E+04
The data available in the .flt file is:
Result Entity
Details
Subcase
Number of the subcase.
CONFIGURATION
Identifies the databases associated with the aerodynamics. Currently, the aerodynamic model is computed from the Bulk Data Entries of the analysis deck and the corresponding database is denoted by AEROSG2D.
XY-SYMMETRY and XY-SYMMETRY
Symmetry flags from the AESYMXY and AESYMXZ entries.
POINT
Point of the flutter analysis.
For the K method, this denotes a reduced frequency.
For the KE, PK and PKNL methods, this denotes a mode number.
MACH NUMBER
Mach number specified in FLFACT entry.
The FLACT entry is referenced in a FLUTTER entry, that is referenced in the corresponding subcase through the FMETHOD entry.
DENSITY RATIO
Density ratio specified in FLFACT entry.
The FLACT entry is referenced in a FLUTTER entry, that is referenced in the corresponding subcase through the FMETHOD entry.
METHOD
Method of flutter analysis.
KFREQ
Reduced frequency specified in the FLFACT entry.
The FLACT entry is referenced in a FLUTTER entry, that is referenced in the corresponding subcase through the FMETHOD entry.
Velocity
Velocities calculated from the complex eigenvalues.
Damping
Damping calculated from the complex eigenvalues.
Complex eigenvalue
Calculated complex eigenvalues in the flutter analysis.

Comments

  1. For more details on flutter analysis and output, refer to Dynamic Aeroelastic Analysis in the User Guide.