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BModes is a finite-element code that provides dynamically coupled modes for a beam.

The beam can be a rotor blade, rotating or non-rotating, or a tower. Both the blade and the tower can have a tip attachment. The tip attachment is assumed to be rigid body with mass, six moments of inertia, and a mass centroid that may be offset from the blade or tower axis. Examples of tip attachments are aerodynamic brakes for blades and rotor-nacelle assemblies for towers. In addition to the tip inertia, the tower can also have tension-wire supports. Both the tip inertias and tension support wires can substantially influence the coupled modes mentioned earlier, especially for a tower.

Wind turbine designers may use coupled modes for several applications such as modal-based modeling of blades and tower for validation of flexible-component models using experimental data, modal-based fatigue analysis, and interpretation of aeroelastic-stability behavior of turbines. BModes can be used to generate the blade and tower mode shapes used by the ElastoDyn module of FAST/OpenFAST.

BModes requires specification of rotor speed, blade geometry, precone, pitch control setting, and structural properties distribution along the blade as inputs. These properties may be obtained from experimental tests, blade manufacturer, or a properties-extractor code, such as PreComp or BPE. The current version of BModes can handle only metallic or isotropic composite blades.

The code and user's guide assume the user has basic familiarity with coupled modes. Please note that due to budgetary and time constraints, the code has not been fully commented or documented. Therefore, we will not be able to entertain any questions on the source code.

This software was developed by Gunjit Bir of NREL, based on the University of Maryland Advanced Rotorcraft Code.

Note: NREL is not furthering the development this software. The links below are provided for archival purposes only.


BModes Change Log (v1.03.01, 2 KB, 20-March-2008)

This is a list of changes made to the code. Look at this text file to see if we've made worthwhile changes since you received your previous version of BModes.

BModes User's Guide (v1.30, 178 KB, 27-September-2007)

This is a draft of the BModes User's Guide. Please refer to it when trying to understand how the program works.