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$               RIGID FORMAT No. 10 (APP AERO), Aeroelastic Analysis
$          Aeroelastic Flutter Analysis of a 15 Degree Swept Wing (10-2-1)
$ 
$ A. Description
$ 
$ This problem illustrates the use of the aeroelastic analysis to determine
$ flutter frequencies and mode shapes for an untapered wing having 15 degree
$ sweep and an aspect ratio of 5.34.
$ 
$ B. Input
$ 
$ Bulk data cards used include CAERO1, PAERO1, SPLINE2, SET1, AERO, MKAERO1,
$ FLUTTER, and FLFACT as illustrated in User's Manual Section 1.11.
$ 
$ C. Theory
$ 
$ Reference 22 specifies the reduced frequency k = .1314 (p.17) frequency
$ ratio w/w      = 0.51 (p.35) and torsion frequency w      = 1488 (p.17).
$          alpha                                      alpha
$ 
$ The flutter velocity is found from
$ 
$                 REFC              w
$                 ---- x w      x ------
$                  2      alpha   w
$          bw                      alpha
$    V  =  --  =  -----------------------  =  5980 in/sec.                   (1)
$          k                 k
$ 
$ where REFC is the reference length input on the AERO bulk data card.
$ 
$ The flutter frequency is found from
$ 
$                     w
$          w      x ------
$           alpha   w
$                    alpha
$    f  =  ----------------  =  121 Hz                                       (2)
$              2 pi
$ 
$ D. Results
$ 
$ The results obtained are compared with both theoretical results using the
$ modified strip analysis method and with experimental results. The flutter
$ velocity is in good agreement.
$ 
$ Frequencies are automatically output while mode shapes used in the modal
$ formulation are obtained using an ALTER to the Rigid Format following the Real
$ Eigenvalue Analysis Module.
$ 
$ Mode shapes for all points in the model may be obtained by checkpointing the
$ problem using the Normal Mode Analysis (Rigid Format 3) and subsequently
$ restarting using the Aeroelastic Analysis.
$ 
$ APPLICABLE REFERENCES
$ 
$ 22. Yates. E. C. and R. M. Bennett, "Use of Aerodynamic Parameters From
$     Nonlinear Theory in Modified-Strip-Analysis Flutter Calculations for
$     Finite-Span Wings at Supersonic Speeds"; NASA TN D-l824, July 1963.
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