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Full-Text Articles in Engineering
Least-Squares Finite Element Formulation For Fluid-Structure Interaction, Cody C. Rasmussen
Least-Squares Finite Element Formulation For Fluid-Structure Interaction, Cody C. Rasmussen
Theses and Dissertations
Fluid-structure interaction problems prove difficult due to the coupling between fluid and solid behavior. Typically, different theoretical formulations and numerical methods are used to solve fluid and structural problems separately. The least-squares finite element method is capable of accurately solving both fluid and structural problems. This capability allows for a simultaneously coupled fluid structure interaction formulation using a single variational approach to solve complex and nonlinear aeroelasticity problems. The least-squares finite element method was compared to commonly used methods for both structures and fluids individually. The fluid analysis was compared to finite differencing methods and the structural analysis type compared …
Dynamic Aeroelastic Analysis Of Wing/Store Configurations, Gregory H. Parker
Dynamic Aeroelastic Analysis Of Wing/Store Configurations, Gregory H. Parker
Theses and Dissertations
Limit-cycle oscillation, or LCO, is an aeroelastic phenomenon characterized by limited amplitude, self-sustaining oscillations produced by fluid-structure interactions. In order to study this phenomenon, code was developed to interface a modal structural model with a commercial computational fluid dynamics program. LCO was simulated for a rectangular wing, referred to as the Goland+ wing. It was determined that the aerodynamic nonlinearity responsible for LCO in the Goland+ wing was the combination of strong trailing-edge and lambda shocks which periodically appear and disappear. This mechanism limited the flow of energy into the structure which quenched the growth of the flutter, resulting …
Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman
Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman
Theses and Dissertations
There is a growing interest in understanding how uncertainties in flight conditions and structural parameters affect the character of a limit cycle oscillation (LCO) response, leading to failure of an aeroelastic system. Uncertainty quantification of a stochastic system (parametric uncertainty) with stochastic inputs (initial condition uncertainty) has traditionally been analyzed with Monte Carlo simulations (MCS). Probability density functions (PDF) of the LCO response are obtained from the MCS to estimate the probability of failure. A candidate approach to efficiently estimate the PDF of an LCO response is the stochastic projection method. The objective of this research is to extend the …
Nonlinear, Transonic Flutter Prediction For F-16 Stores Configuration Clearance, Raymond G. Toth
Nonlinear, Transonic Flutter Prediction For F-16 Stores Configuration Clearance, Raymond G. Toth
Theses and Dissertations
Wing flutter, or more accurately limit cycle oscillation (LCO), has been an issue for the F-16 since its operational deployment. Different store configurations and the permutations of those configurations after weapons are released will cause LCO to either disappear or appear. Unfortunately, the current method used by engineers for predicting LCO onset is based on linear, subsonic aerodynamic theory with no corrections for transonic effects. Predictions using this method are often good in frequency, but can be far off in predicting onset speed, forcing flutter engineers to rely more on experience and interpolation from similar configurations to design flight test …
Techniques For Reduced Order Modeling Of Aeroelastic Structures With Deforming Grids, John S. R. Anttonen
Techniques For Reduced Order Modeling Of Aeroelastic Structures With Deforming Grids, John S. R. Anttonen
Theses and Dissertations
Reduced order modeling (ROM) seeks to make the modeling of aeroelastic behavior practical by reducing computation time for design codes. Deforming grids are often used in aeroelastic problems to account for the deformation of the structure. Proper Orthogonal Decomposition (POD/ROM) is a ROM technique that operates in an index-space for computations, not accounting for changes in grid dynamics, and must be modified to reflect grid deformation properly. To investigate and account for the effects of grid deformation on POD/ROM, a new algorithm is developed that incorporates modifications to the usual formulation. Evaluation of the new algorithm is accomplished through application …