Exposed to spectral and uniform light, a one-dimensional, conducting and radiatively participating medium due to embedded absorbing and scattering gold nanoshells is solved. P1 Approximation method is used to solve the radiative transfer equation and finite difference explicit method is used to find the temperature distribution having both boundaries subjected to convection. The host medium was transparent to spectral radiation and the temperature distribution is obtained when the temperature of the irradiated boundary reaches the desired temperature such that any temperature in the medium does not exceed the melting temperature of the host medium. Variation of the concentration and configuration of gold nanoshells are found to change the radiative transfer spectrum that leads to an alteration in the local heat generation spectrum and the desired temperature distribution.

Acoustic levitation permits the observation of individual oscillating liquid droplets. Droplet shape oscillation data lead to thermophysical property measurements without the contaminating effects of a solid container. For spherical droplets, analysis has shown natural frequencies are a function of droplet size, mode number, and the surface tension and density of the liquid; the damping rate of oscillations has been correlated with the viscosity of the liquid. In terrestrial levitation, however, gravity serves to deform the droplet and split the frequency spectrum. In addition, droplet evaporation causes natural frequencies to change over time. This work compares experimental data on the frequency splitting of water and ethyl alcohol with theoretical predictions. With slight refinements to the theory, good agreement is found. Surface tension and viscosity were also measured; surface tension for distilled water came within 5% of the published value, and a new approach to the measurement of viscosity via levitation is described and tested.

Simulations of complex fluid-object interactions problems in aeronautics demand robust and sophisticated numerical techniques. The proposed B-FOIST is an efficient library-lookup method for predicting the response of an object to a dominant, arbitrary flow field. B-FOIST predicts the trajectory of an object without the need for flow subcomputations, mesh-moving or remeshing. Subsequently, the path of the object can be calculated more quickly and efficiently than traditional mesh-moving methods while producing comparable results. Implementation of the proposed SSTF formulation can improve the efficiency of traditional space-time finite element computations. Many repetitive, unnecessary calculations can be eliminated by reformulating shape function derivatives and re-structuring the element-level matrix/vector calculations. There is the potential for large computational savings depending on the previous structure of the computations.

The permanent deformation of a rigid perfectly-plastic unsupported thin ring subjected to a concentrated time-dependent force acting along a diameter is calculated. The analysis is developed for a force pulse of arbitrary shape, and numerical results are obtained for the special case of a triangular force pulse. It is shown that, for sufficiently large values of the applied force, four plastic hinges develop along the ring. Two of the hinges are fixed, and the other two move along the ring as the force varies with time. The motion of the hinges is governed by a system of coupled nonlinear ordinary differential equations that are solved numerically. The parameters that describe the final plastic deformation of the ring are evaluated and shown graphically. Previous studies of this problem provided a numerical solution for the case of a rectangular pulse only.

A family of air-to-surface guidance laws designed to intercept moving targets has been developed. They include the effect of gravity, as well as constraints on the terminal flight path and heading angle, and are designed for tracking moving targets. These guidance laws yield equations for the commanded accelerations. They are based firmly on optimal control theory and meet the first and second variation necessary conditions that originate from Pontryagin's Minimum Principle. In addition, these solutions also meet the second variation sufficient conditions for a minimum. They have been evaluated in six degree of freedom simulations. The results show that they perform as designed, even for airframes which are rather sluggish.

In the future, the arsenal of the U.S. military will include Space-delivered weapons, released by reusable launch vehicles. Entry vehicles released from the launch platforms will be capable of guiding to target locations throughout the world. In order to adequately incorporate these weapons into military plans, theater commanders will require sophisticated planning algorithms to maximize the likelihood of destroying the most important targets. This thesis develops a target assignment algorithm which uses a sequence of linear auctions to optimize the assignment of entry vehicles to weighted targets. This result can be improved over time by use of a directed search method, which uses numerous sequences of linear auctions to improve on solutions by eliminating poor assignments. These methods are compared to greedy methods, showing improvement in the assignment solution.

The behavior of a nanoscale fluid system in the subcritical region is investigated using molecular simulation. The fluid used is argon and the intermolecular forces are represented by the Lennard-Jones potential. The simulations show that the phase change in a nanoscale system becomes continuous as opposed to the constant temperature and constant pressure phase change for a macroscale system. Then nonlinear curve fitting was performed using two cubic equations to obtain a representation of the simulation data. The continuous phase change behavior predicted by the molecular simulation is verified by using an approximate analytical analysis. A cubical system is defined for five different configurations based on the minimization of the interfacial surface area. These systems are then analyzed to define their thermodynamic behavior by using a technique to minimize the Helmholtz free energy. It is also shown how this continuous phase change alters the behavior of nanoscale thermal systems in subcritical thermodynamic cycles. A nanoscale vapor heat engine shows a lower efficiency than the macroscale vapor heat engine and the coefficient of performance for a nanoscale refrigeration cycle is higher than that for a macroscale refrigeration cycle.

We present here for the first time a successful 3D implementation of the Edge-Tracked Interface Locator Technique (ETILT) over the Deforming Spatial-Domain/Stabilized Space-Time (DSD/SST) formulation thus allowing the simulation of moving objects in multiple fluid flows. While the DSD/SST technique allows us to track solid-fluid interfaces, ETILT lets us capture fluid-fluid interfaces accurately, forming one approach to Mixed Interface-Tracking/Interface-Capturing Technique (MITICT). Based on the well-known Volume-of-Fluid (VOF) method where the interface location is captured with an interface function governed by the advection equation, in ETILT an edge representation is formed over the nodal representation to increase accuracy. Several different approaches are discussed to project from the nodal level to the edge level and vice versa accurately and efficiently. The reverse projection from the edge to the node level is established through a penalty formulation which ensures that the accuracy obtained in the edge level is passed correctly to the node level. A 3D volume conservation scheme based on tetrahedral elements that uses accuracy gained in the edge representation is introduced to prevent the volume errors present in the standard Volume of Fluid (VOF) method. The different projection strategies, the 3D tetrahedral volume conservation scheme, and the MITICT formulation is tested through several numerical problems. The numerical scheme is evaluated using the well-known broken dam problem. The results not only agree very well with the literature, but prove to be insightful. The collapse of a cylindrical water column is computed to add the literature an easy to reproduce 3D benchmark problem in free surface flows. In order to deal with sharp corners and flows where the interface hits a wall, improvements are suggested and presented by the filling of a step mold problem. Lastly, the method's capability to model moving objects in multiple fluid environments is presented by the simulation of an oscillating cylinder through the interface between water and air.

While some engineers use computers as a first line of attack on design problems, others are persistently making computers and their software faster and more capable of solving realistic problems. The technology used to build the microscale electronic components that makes computers fast is also used to construct micron-scale electromechanical (MEMS) actuators ideal for use in control schemes to reduce drag in industrial flows, promising millions of dollars in cost savings. The Immersed Boundary Condition (IBC) developed here augments a common fractional step, pseudospectral method used with Large Eddy Simulation to inexpensively and more realistically simulate turbulent flow over MEMS-like actuators. This is done by augmenting the numerical method to simulate flow over unsteady, irregular boundaries with static, structured rectilinear grids. The method is validated and applied to evaluate actuator characteristics and simulate open and closed loop flow control with continuous and discrete, MEMS-like actuators.

A new means of heat transfer known as the piston effect was identified in 1989. The piston effect is where the expanding thermal boundary layer acts like a piston which compresses the bulk fluid. An examination of the equations for the conservation of mass, momentum, and energy identified the significant thermophysical properties as the thermal conductivity, the volume expansivity, and the isothermal compressibility. The thermal conductivity and the volume expansivity determine the thickness of the thermal boundary layer. The isothermal compressibility of the bulk fluid determines the pressure response of the bulk fluid to a given volume change. Previous researchers used only the van der Waals equation of state at conditions within mK of the critical point. The research described herein focuses on the pressure response of a fluid near the critical point to a sudden change in the boundary temperature. The use of the van der Waals equation of state for numerical simulation of the piston effect results in underpredicting the magnitude of the pressure wave by approximately 30 percent while overpredicting the acoustic heating by approximately 15 percent compared to using all fluid properties from a real gas equation of state. When evaluating the piston effect at conditions typical of cryogenic storage systems the pressure response of the fluid was observed to be six orders of magnitude larger than had been previously reported. The extent of the acoustic heating resulted in temperature increases in the bulk fluid that were four orders of magnitude larger. The real gas equation of state was used to compare the pressure and temperature response of oxygen and hydrogen due to a thermal disturbance at the boundary. The pressure rise in hydrogen after five acoustic time periods was only 17% of the pressure rise in oxygen. The temperature increase in hydrogen was only 30% of the temperature rise in oxygen. On the diffusion time scale the pressure rise in the oxygen is an order of magnitude larger than the pressure rise in hydrogen for the same thermal penetration depth. The temperature rise in oxygen is four times greater than the temperature rise in hydrogen.