Dynamic stall deeply affects the response
of helicopter rotor blades, making its modeling accuracy very important. Two commonly used dynamic stall models were implemented
in a comprehensive code, validated, and contrasted to provide improved analysis
accuracy and versatility. Next, computational fluid dynamics and computational structural dynamics loose coupling methodologies are reviewed, and a general tight coupling approach was implemented and tested. The tightly coupled
computational fluid dynamics and computational structural dynamics methodology is then used to assess the stability characteristics of complex rotorcraft problems. An aeroelastic analysis of rotors must include an assessment of
potential instabilities and the determination of damping ratios for all modes of interest. If
the governing equations of motion of a system can be formulated as linear, ordinary
differential equations with constant coefficients, classical stability evaluation
methodologies based on the characteristic exponents of the system can rapidly and
accurately provide the system's stability characteristics. For systems described by linear,
ordinary differential equations with periodic coefficients, Floquet's theory is the preferred
approach. While these methods provide excellent results for simplified linear models with
a moderate number of degrees of freedom, they become quickly unwieldy as the number
of degrees of freedom increases. Therefore, to accurately analyze rotorcraft aeroelastic
periodic systems, a fully nonlinear, coupled simulation tool is used to determine the
response of the system to perturbations about an equilibrium configuration and determine
the presence of instabilities and damping ratios. The stability analysis is undertaken using
an algorithm based on a Partial Floquet approach that has been successfully applied with
computational structural dynamics tools on rotors and wind turbines. The stability analysis approach is computationally
inexpensive and consists of post processing aeroelastic data, which can be used with any
aeroelastic rotorcraft code or with experimental data.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/43579 |
| Date | 17 January 2012 |
| Creators | Zaki, Afifa Adel |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Detected Language | English |
| Type | Dissertation |
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