Griffith, D. Todd
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/6193
Todd Griffith in an Associate Professor of Mechanical Engineering. Among his many research interests are:
- Structural dynamics
- Aero-elastics
- Dynamics and control
- Structural health monitoring and prognostics management
- Design
- Experimental and analytical methods
- Reduced order modeling
- Model validation
- Uncertainty Quantification.
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Recent Submissions
Item Assessment of Flutter Prediction and Trends in the Design of Large-Scale Wind Turbine Rotor Blades(Published under licence by IOP Publishing Ltd.) Griffith, D. Todd; Chetan, Mayank; Griffith, D. Todd; Chetan, MayankWith the progression of novel design, material and manufacturing technologies, the wind energy industry has successfully produced larger and larger wind turbine rotor blades while driving down the levelized cost of energy (LCOE). Though the benefits of larger turbine blades are appealing, larger blades are prone to instabilities due to their long and slender nature, and one of the concerning aero-elastic instabilities of these blades is classical flutter. In this work we assess classical flutter prediction tools for predicting flutter speeds in the design of large blades. Flutter predictions are benchmarked against predictions of previous studies. Then, we turn to the main focus of the study, which is design to mitigate flutter. Trends in flutter speeds and flutter mode shapes are examined for a series of 100-meter blade designs. Then, a sensitivity study is performed to assess the impacts of blade design choices (e.g. materials choice and material placement) on flutter speed in a redesign study of a lightweight 100-meter blade with small flutter margin. A new design is developed to demonstrate the ability to increase the flutter speed while reducing blade mass through structural design.Item Integrated System Design for a Large Wind Turbine Supported on a Moored Semi-Submersible Platform(MDPI AG, 2018-10-22) Liu, J.; Thomas, E.; Manuel, L.; Griffith, D. Todd; Ruehl, K. M.; Barone, M.; Griffith, D. ToddOver the past few decades, wind energy has emerged as an alternative to conventional power generation that is economical, environmentally friendly and, importantly, renewable. Specifically, offshore wind energy is being considered by a number of countries to harness the stronger and more consistent wind resource compared to that over land. To meet the projected “20% energy from wind by 2030” scenario that was announced in 2006, 54 GW of added wind energy capacity need to come from offshore according to a National Renewable Energy Laboratory (NREL) study. In this study, we discuss the development of a semi-submersible floating offshore platform with a catenary mooring system to support a very large 13.2-MW wind turbine with 100-m blades. An iterative design process is applied to baseline models with Froude scaling in order to achieve preliminary static stability. Structural dynamic analyses are performed to investigate the performance of the new model using a finite element method approach for the tower and a boundary integral equation (panel) method for the platform. The steady-state response of the system under uniform wind and regular waves is first studied to evaluate the performance of the integrated system. Response amplitude operators (RAOs) are computed in the time domain using white-noise wave excitation; this serves to highlight nonlinear, as well as dynamic characteristics of the system. Finally, selected design load cases (DLCs) and the stochastic dynamic response of the system are studied to assess the global performance for sea states defined by wind fields with turbulence and long-crested irregular waves.