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Issures In Discontinuous High-Order Methods: Broadband Wave Computation And Viscous Boundary Layer Resolution, Yi Li 2010 Iowa State University

Issures In Discontinuous High-Order Methods: Broadband Wave Computation And Viscous Boundary Layer Resolution, Yi Li

Graduate Theses and Dissertations

A new discontinuous formulation named Correction Procedure via Reconstruction (CPR) was developed for conservation laws. CPR is an efficient nodal differential formulation unifying the discontinuous Galerkin (DG), spectral volume (SV) and spectral difference (SD) methods, is easy to implement. In this thesis, we deal with two issues: the efficient computation of broadband waves, and the proper resolution of a viscous boundary layer with the high-order CPR method.

A hybrid discontinuous space including polynomial and Fourier bases is employed in the CPR formulation in order to compute broad-band waves. The polynomial bases are used to achieve a certain order of accuracy ...


Focusing Aberration Corrections For Ultrasonic Inspections Of Disk Forgings When Using A Surface Compensating Mirror And Segmented Annular Phased Array, Jon Hiram Friedl 2010 Iowa State University

Focusing Aberration Corrections For Ultrasonic Inspections Of Disk Forgings When Using A Surface Compensating Mirror And Segmented Annular Phased Array, Jon Hiram Friedl

Graduate Theses and Dissertations

Phased array transducers are playing an increasing role in ultrasonic nondestructive evaluation inspection applications, and one area of their use is in the inspection of critical jet engine components such as titanium alloy turbine disk forgings. Inspection of these forging disks is performed during stages of their manufacturing, particularly at an intermediate stage when the forging disk has a deliberate "sonic shape." A forging's sonic shape, from which the final disk shape will be machined, is conducive to ultrasonic testing inspections due to its simple entry surfaces. These entry surfaces are primarily planar or conical surfaces.

In prior work ...


Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D. 2010 University of Nebraska at Lincoln

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.

Faculty Publications from the Department of Engineering Mechanics

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as ...


Quadrature-Based Moment Model For Moderately Dense Polydisperse Gas-Particle Flows, Rodney O. Fox, Prakash Vedula 2010 Iowa State University

Quadrature-Based Moment Model For Moderately Dense Polydisperse Gas-Particle Flows, Rodney O. Fox, Prakash Vedula

Chemical and Biological Engineering Publications

A quadrature-based moment model is derived for moderately dense polydisperse gas-particle flows starting from the inelastic Boltzmann-Enskog kinetic equation including terms for particle acceleration (e.g., gravity and fluid drag). The derivation is carried out for the joint number density function, f(t,x,m,u), of particle mass and velocity, and thus, the model can describe the transport of polydisperse particles with size and density differences. The transport equations for the integer moments of the velocity distribution function are derived in exact form for all values of the coefficient of restitution for particle-particle collisions. For particular limiting cases, the ...


Active Control Of Shocks And Sonic Boom Ground Signal, Bedri Yagiz 2010 Old Dominion University

Active Control Of Shocks And Sonic Boom Ground Signal, Bedri Yagiz

Mechanical & Aerospace Engineering Theses & Dissertations

The manipulation of a flow field to obtain a desired change is a much heightened subject. Active flow control has been the subject of the major research areas in fluid mechanics for the past two decades. It offers new solutions for mitigation of shock strength, sonic boom alleviation, drag minimization, reducing blade-vortex interaction noise in helicopters, stall control and the performance maximization of existing designs to meet the increasing requirements of the aircraft industries. Despite the wide variety of the potential applications of active flow control, the majority of studies have been performed at subsonic speeds. The active flow control ...


An Uncertainty Quantification Of The Variation Of Internal Heat Transfer Coefficients And The Effect On Airfoil Life, Jan H. Marsh 2010 University of Central Florida

An Uncertainty Quantification Of The Variation Of Internal Heat Transfer Coefficients And The Effect On Airfoil Life, Jan H. Marsh

Electronic Theses and Dissertations

Uncertainty in accurately knowing applied internal heat transfer coefficients inside of a cooling passage can lead to variability in predicting low cycle fatigue life of a turbine vane or blade. Under-predicting a life value for a turbine part can have disastrous effects on the engine as a whole, and can negate efforts in innovative design for advanced cooling techniques for turbine components. Quantification of this fatigue life uncertainty utilizing a computational framework is the primary objective of this thesis. Through the use of probabilistic design methodologies a process is developed to simulate uncertainties of internal heat transfer coefficient, which are ...


Thermal Performance Of Cryogenic Multilayer Insulation At Various Layer Spacings, Wesley Louis Johnson 2010 University of Central Florida

Thermal Performance Of Cryogenic Multilayer Insulation At Various Layer Spacings, Wesley Louis Johnson

Electronic Theses and Dissertations

Multilayer insulation (MLI) has been shown to be the best performing cryogenic insulation system at high vacuum (less than 10-3 torr), and is widely used on spaceflight vehicles. Over the past 50 years, many numerous investigations of MLI have yielded a general understanding of the many variables associated with MLI. MLI has been shown to be a function of variables such as warm boundary temperature, the number of reflector layers, and the spacer material in between reflectors, the interstitial gas pressure and the interstitial gas. Because conduction between reflectors increases with the thickness of the spacer material, and yet the ...


Analysis Of Wake Vortices Of A Medium Range Twin-Propeller Military Cargo Aircraft Using Statistically Designed Experiments, Burhan Sahin 2010 Old Dominion University

Analysis Of Wake Vortices Of A Medium Range Twin-Propeller Military Cargo Aircraft Using Statistically Designed Experiments, Burhan Sahin

Mechanical & Aerospace Engineering Theses & Dissertations

An experimental study was initiated to analyze the trajectories of the streamwise vortices behind the wing tip and flap of a medium range and propeller driven twin-engine military cargo aircraft. The model used for the experimental study was a generic, high wing and half model of a propeller driven aircraft and mounted within Old Dominion University's Low Speed Wind Tunnel where the wind tunnel flow speed was set to constant value of 9 m/sec. The main purpose of the study was to reach regression models for the motion and vorticity strength of both vortices under varying factors such ...


Constrained Optimal Orbit Design For Earth Observation, Sharon D. Vtipil 2010 Old Dominion University

Constrained Optimal Orbit Design For Earth Observation, Sharon D. Vtipil

Mechanical & Aerospace Engineering Theses & Dissertations

The purpose of this dissertation is to demonstrate use requirements for a satellite observation mission can be used to determine a constrained optimal orbit based on observation site requirements, observation condition restraints, and sensor characteristics. The typical Earth observation satellite is first designed according to an appropriate orbit; then the observation requirements are used to develop a target schedule. The new design process outlines the development of the appropriate orbit by incorporating user requirements at the forefront of mission planning, not after an orbit has been selected. This research shows how to map the user requirements into constraints for the ...


Solution Approximation For Atmospheric Flight Dynamics Using Volterra Theory, Ashraf Mohammed Kandeel Omran 2010 Old Dominion University

Solution Approximation For Atmospheric Flight Dynamics Using Volterra Theory, Ashraf Mohammed Kandeel Omran

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation introduces a set of novel approaches in order to facilitate and enrich Volterra theory as a nonlinear approximation technique for constructing mathematical solutions from the governing relationships describing aircraft dynamic behavior. These approaches reconnect Volterra theory and flight mechanics research, which has not been addressed in the technical literature for over twenty years. Volterra theory is known to be viable in modeling weak nonlinearities, but is not particularly well suited for directly describing high performance aircraft dynamics. In order to overcome these obstacles and restrictions of Volterra theory, the global Piecewise Volterra Approach has been developed. This new ...


Multiscale Modeling Of Tio2 Nanoparticle Production In Flame Reactors: Effect Of Chemical Mechanism, Maulik Mehta, Yonduck Sung, Venkatramanan Raman, Rodney O. Fox 2010 Iowa State University

Multiscale Modeling Of Tio2 Nanoparticle Production In Flame Reactors: Effect Of Chemical Mechanism, Maulik Mehta, Yonduck Sung, Venkatramanan Raman, Rodney O. Fox

Chemical and Biological Engineering Publications

For titanium dioxide (TiO2) nanoparticles manufactured in flame reactors, the precursor is injected into a pre-existing flame, exposing it to a high-temperature gas phase, leading to nucleation and particle growth. Predictive modeling of this chemical process requires simultaneous development of detailed chemical mechanisms describing gas-phase combustion and particle evolution, as well as advanced computational tools for describing the turbulent flow field and its interactions with the chemical processes. Here, a multiscale computational tool for flame-based TiO2 nanoparticle synthesis is developed and a flamelet model representing detailed chemistry for particle nucleation is proposed. The effect of different chemical mechanisms ...


Flight Attendant/Pilot Communication, In A Post 9/11 Environment: Viewed From Both Sides Of The Fortress Door"., Lori Brown 2009 Western Michigan University

Flight Attendant/Pilot Communication, In A Post 9/11 Environment: Viewed From Both Sides Of The Fortress Door"., Lori Brown

Lori J. Brown

Reports and a recent global survey (Brown, et al., 2010) reported that out of 271 pilots and flight attendants, 13% indicated a discrete wireless communication device would not enhance safety, 18% indicate a slight effect, 33% indicated a device may somewhat enhance safety, and 21% indicated the device would greatly enhance safety. ...


Erau Aviation Wildlife Hazard Newsletter, Paul F. Eschenfelder 2009 Embry Riddle Aeronautical University - Daytona Beach

Erau Aviation Wildlife Hazard Newsletter, Paul F. Eschenfelder

Paul F. Eschenfelder

No abstract provided.


Chemistry Model For Ablating Carbon-Phenolic Material During Atmospheric Re-Entry, Alexandre Martin, Iain D. Boyd, Ioana Cozmuta, Michael J. Wright 2009 University of Michigan - Ann Arbor

Chemistry Model For Ablating Carbon-Phenolic Material During Atmospheric Re-Entry, Alexandre Martin, Iain D. Boyd, Ioana Cozmuta, Michael J. Wright

Alexandre Martin

Recent and future re-entry vehicle designs, such as the CEV, use ablative material as the main component of the heat shield of their thermal protection system. In order to properly predict the behavior of the vehicle, it is imperative to take into account the gases produced by the ablation process when modeling the reacting flow environment. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled in the boundary layer is complex and might lead to thermal chemical reactions that cannot be captured with simple flow chemistry ...


Airport Wildlife Hazard Control, Paul F. Eschenfelder 2009 Embry Riddle Aeronautical University - Daytona Beach

Airport Wildlife Hazard Control, Paul F. Eschenfelder

Paul F. Eschenfelder

No abstract provided.


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