Aeroelastic flutter analysis (SOL 145)

You can perform an aeroelastic flutter analysis in Pre/Post using the Simcenter Nastran SOL 145 Aeroelastic Flutter solution sequence.

Pre/Post supports the following aeroelastic flutter analysis methods:

• K-methodThe K-method is a variation of the traditional American flutter method developed by the Air Materiel Command.

• KE-methodThe KE-method is also based on the American flutter method and is more efficient at tracking roots than the K-method. However, it cannot account for viscous damping and does not output eigenvectors.

• PK-methodThe PK-method is similar to the British flutter method, which was developed by the Royal Aircraft Establishment.

• PKNL-methodThe PKNL-method is the PK-method without looping over Mach number, density ratio, and velocity.

The aerodynamic conditions such as Mach number, density, and so on that you must define depend on the aeroelastic flutter analysis method. For example, when you select the K-method, you must specify the range of densities, Mach numbers, and reduced frequencies over which to perform the aeroelastic flutter analysis.

When you specify densities, you can define them directly, or you can specify altitudes and let Pre/Post calculate the corresponding densities from the International Standard Atmosphere (ISA).

To reduce the computational effort required to complete an aeroelastic flutter analysis, you can specify a real modal reduction. Because the number of modes that you retain may be large, in Pre/Post you can optionally limit the modes that Simcenter Nastran outputs to those with the lowest frequencies.

Simulation objects

For aeroelastic flutter analysis, you create following simulation objects:

• Aero Spline Creates the spline that interfaces the structural mesh with the aerodynamic panel mesh.

• Aero Element Correction Factor Defines the optional correction factors that adjust the force and moment so that they agree with experimental data for incidence changes.

Modeling objects

For aeroelastic flutter analysis, you create the following modeling objects:

• Aerodynamic ParametersDefines the reference chord length, reference density, and, if applicable, planes of symmetry.

• Aerodynamic Flutter DataDefines the flutter analysis method and aerodynamic conditions such as Mach number, density ratio, and so on, at which to perform the flutter analysis.

• Aerodynamic Matrix - Mach Number and Reduced Frequency TableDefines a table of Mach numbers versus reduced frequencies.When you create this table, the range of Mach numbers and reduced frequencies must encompass the full range of aerodynamic conditions.

Constraints

You can perform an aeroelastic flutter analysis on an unconstrained (free-free) model or a constrained model.

Post-processing options

Simcenter Nastran writes the flutter analysis results and model geometry to an OP2 file where Pre/Post can access it for post-processing and plotting. Customarily, a plot of damping versus velocity (V-g plot) or frequency versus velocity (V-f plot) are used to identify the speed at which aeroelastic flutter occurs.

For information on how to create a V-g or V-f plot, see Create V-g and V-f plots.

The results that Simcenter Nastran writes to the OP2 file includes:

• Aerodynamic panel geometry defined as Q4AERO and T3AERO elements is written to the GEOM2 data block.Q4AERO and T3AERO elements are elements that Simcenter Nastran generates during the aeroelastic flutter analysis solve.

• Normal modes and the corresponding mode shapes defined relative to the structural and aerodynamic meshes are written to an OUGV1 data block.

• Complex modes and the corresponding complex mode shapes defined relative to the structural and aerodynamic meshes are written to an OUGV1 data block.

• Damping, frequency, and velocity data for XY plotting are written to the OVG data block.

Additional information

For a summary of the aeroelastic flutter analysis capability in Simcenter Nastran SOL 145, see the Simcenter Nastran Advanced Dynamic Analysis User's Guide in the Aeroelastic Solutions section of the Dynamic Solution Techniques chapter.

For complete information on the aeroelastic flutter analysis capability in Simcenter Nastran SOL 145, including the underlying aeroelastic theory and sample problems, see the Simcenter Nastran Aeroelastic Analysis User's Guide.

Where do I find it?

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partSimcenter Nastran as the specified solverStructural as the specified analysis type
Command Finder	Solution

How do I

Create a mesh of aero panels

Create an aero spline

Define aerodynamic parameters

Define flutter method and aerodynamic conditions

Create M versus k table

Assign a modeling object to a solution or solution subcase

Assign an aerodynamic matrix modeling object to the solution

Create V-g and V-f plots

Learn more

Aeroelastic flutter analysis workflow (SOL 145)

Post-processing aeroelastic flutter analysis results

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Aeroelastic flutter analysis (SOL 145), Simcenter 3D 2021.1 Series

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