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Articles 1  9 of 9
FullText Articles in Engineering
Buckling Analysis And Optimum Design Of Multidirectionally Stiffened Composite Curved Panel, Navin R. R. Jaunky
Buckling Analysis And Optimum Design Of Multidirectionally Stiffened Composite Curved Panel, Navin R. R. Jaunky
Mechanical & Aerospace Engineering Theses & Dissertations
Continuous filament gridstiffened structure is a stiffening concept that combines structural efficiency and damage tolerance. However, buckle resistant design optimization of such structures using a finite element method is expensive and time consuming due to the number of design parameters that can be varied. An analytical optimization procedure which is simple, efficient and supports the preliminary design of gridstiffened structures for application to combined loading cases is needed.
An analytical model for a general gridstiffened curved panel is developed using an improved smeared theory with a firstorder, sheardeformation theory to account for transverse shear flexibilities and local skinstiffener interaction effects ...
An Experimental Investigation Of Wall Cooling Effects On Hypersonic Boundary Layer Stability In A Quiet Wind Tunnel, Alan E. Blanchard
An Experimental Investigation Of Wall Cooling Effects On Hypersonic Boundary Layer Stability In A Quiet Wind Tunnel, Alan E. Blanchard
Mechanical & Aerospace Engineering Theses & Dissertations
One of the primary reasons for developing quiet tunnels is for the investigation of highspeed boundarylayer stability and transition phenomena without the transitionpromoting effects of acoustic radiation from tunnel walls. In this experiment, a flaredcone model under adiabatic and cooledwall conditions was placed in a calibrated, 'quiet' Mach 6 flow and the stability of the boundary layer was investigated using a prototype constantvoltage anemometer. The results were compared with linearstability theory predictions and good agreement was found in the prediction of secondmode frequencies and growth. In addition, the same 'N=10' criterion used to predict boundarylayer transition in subsonic, transonic ...
Nonlinear Transient Thermal Analysis By The ForceDerivative Method, Narayani V. Balakrishnan
Nonlinear Transient Thermal Analysis By The ForceDerivative Method, Narayani V. Balakrishnan
Mechanical & Aerospace Engineering Theses & Dissertations
The forcederivative method (FDM) represents a series of higherorder modal methods which offer an increasingly improved approximation of the higher modes neglected in the basic modedisplacement method (MDM). The FDM includes additional terms which involve the forcing function and derivatives of the forcing function with respect to time. The modeacceleration method (MAM), extensively used in structural analysis, is a firstorder form of the FDM which includes only one correction term that depends on the forcing function itself. The success of the FDM in many structural dynamic applications has prompted its application for solving transient thermal problems. The superior convergence of ...
Numerical Investigation Of ShockInduced Combustion Past Blunt Projectiles, Jagjit K. Ahuja
Numerical Investigation Of ShockInduced Combustion Past Blunt Projectiles, Jagjit K. Ahuja
Mechanical & Aerospace Engineering Theses & Dissertations
A numerical study is conducted to simulate shockinduced combustion in premixed hydrogenair mixtures at various freestream conditions and parameters. Twodimensional axisymmetric, reacting viscous flow over blunt projectiles is computed to study shockinduced combustion at Mach 5.11 and Mach 6.46 in hydrogenair mixture. A sevenspecies, seven reactions finite rate hydrogenair chemical reaction mechanism is used combined with a finitedifference, shockfitting method to solve the complete set of NavierStokes and species conservation equations. In this approach, the bow shock represents a boundary of the computational domain and is treated as a discontinuity across which RankineHugoniot conditions are applied. All interior ...
Dynamic Unstructured Method For Prescribed And Aerodynamically Determined Relative Moving Boundary Problems, Kamakhya Prasad Singh
Dynamic Unstructured Method For Prescribed And Aerodynamically Determined Relative Moving Boundary Problems, Kamakhya Prasad Singh
Mechanical & Aerospace Engineering Theses & Dissertations
A new methodology is developed to simulate unsteady flows about prescribed and aerodynamically determined moving boundary problems. The method couples the fluid dynamics and rigidbody dynamics equations to capture the timedependent interference between stationary and moving boundaries. The unsteady, compressible, inviscid (Euler) equations are solved on dynamic, unstructured grids by an explicit, finitevolume, upwind method. For efficiency, the grid adaptation is performed within a window around the moving object. The Eulerian equations of the rigidbody dynamics are solved by a RungeKutta method in a noninertial frame of reference. The twodimensional flow solver is validated by computing the flow past a ...
ClosedLoop Identification Of Unstable Systems In Time And Frequency Domains, Hyun Chang Lee
ClosedLoop Identification Of Unstable Systems In Time And Frequency Domains, Hyun Chang Lee
Mechanical & Aerospace Engineering Theses & Dissertations
This dissertation presents closedloop identification algorithms of an unstable system in the time and frequency domains. In the time domain, the projection filter, which is a linear transformation which projects (transforms) a finite number of inputoutput data of a system into its current space, is used to relate the statespace model with a finite difference model. The method developed can take into account the effects of process noise as well as measurement noise and identify openloop systems with unknown feedback dynamics in the closedloop operation. Then the recursive relations between Markov parameters and the ARX model are derived to identify ...
Finite Element Nonlinear Random Response Of Composite Panels Of Arbitrary Shape To Acoustic And Thermal Loads Applied Simultaneously, Roger R. Chen
Finite Element Nonlinear Random Response Of Composite Panels Of Arbitrary Shape To Acoustic And Thermal Loads Applied Simultaneously, Roger R. Chen
Mechanical & Aerospace Engineering Theses & Dissertations
The nonlinear random response of composite plates to the simultaneously applied, combined acoustic/thermal loads are investigated in this dissertation. A finite element formulation for the nonlinear random response is developed. The threenode Mindlin plate element with improved transverse shear is extended and employed. The extension includes the development of the thermal geometric matrix, the mass matrix, the first order and secondorder nonlinear stiffness matrices, and the thermal and mechanical load vectors. An innovative solution procedure has been created which is believed to be the first attempt to analyze nonlinear random response of complex composite panels subjected to simultaneous acoustic ...
Aerodynamic Design Optimization With Consistently Discrete Sensitivity Derivatives Via The Incremental Iterative Method, Vamshi M. Korivi
Aerodynamic Design Optimization With Consistently Discrete Sensitivity Derivatives Via The Incremental Iterative Method, Vamshi M. Korivi
Mechanical & Aerospace Engineering Theses & Dissertations
In this study which involves advanced fluidflow codes, an incremental iterative formulation (also known as the "delta" or "correction" form), together with the wellknown spatially split approximatefactorization algorithm, is presented for solving the large, sparse systems of linear equations that are associated with aerodynamic sensitivity analysis. For the smaller two dimensional problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. However, iterative methods are needed for larger twodimensional and three dimensional applications because direct methods require more computer memory than is currently ...
Component Mode SynthesisBased Design Methodology For Structural Modification And Synthesis, Venkateshwarlu Maroju
Component Mode SynthesisBased Design Methodology For Structural Modification And Synthesis, Venkateshwarlu Maroju
Mechanical & Aerospace Engineering Theses & Dissertations
In this work, structural modification and synthesis techniques based on component mode synthesis are presented. The component mode synthesis method formulates the eigenvalue equation of an entire structure in terms of the vibration characteristics of individual components in the assembly. Through this functional relationship, the individual components are successfully treated as the design entities in the proposed methodology. Unlike conventional design modification techniques that can only treat the properties of the finite elements as the design variables, this technique uses the vibration and static responses of the individual components as the design entities. The sensitivity derivatives of the global responses ...