A nondimensionalized model is developed for a falling, electrically conducting, spherical droplet undergoing equilibrium vaporization. Vaporization is caused by the presence of an external, alternating magnetic field. This model incorporates the influence of magnetic field parameters, phase change, convective heat transfer and radiative heat transfer. The model is used to predict the behavior of a stationary droplet under the same conditions. An experimental electromagnetic vaporization device is designed and constructed. Experimental vaporization rates obtained from the device are found to be in good agreement with numerical results from the stationary model for low power levels. A discrepancy between experimental data and the model for higher power levels is attributed to the formation of a thin metal film in the experimental device.

The flow in a helical duct is characterized by increased fluid mixing, accomplished by the inducement of a secondary flow in the plane normal to the helix centerline. Two independent phenomena interact to produce this secondary flow. First, the curvature of the duct (i.e. its torroidal nature) causes Dean's type recirculation. Second, the torsion due to the non-planarity of the helix causes additional mixing. The secondary flow alters the axial velocity profile and increases the pressure drop compared to a straight duct. Imposing a rectangular cross section on such a duct complicates the analysis compared to a circular or elliptical cross section. A series solution based on curvature is introduced. The components of the series are determined using appropriate eigenfunction expansions. However, the resulting low order solution is limited to low Dean number flows. The analytical solution is useful for flows where curvature (torroidal ducts) or curvature and torsion (helical ducts) are important.

Nanoindentation is a widely recognized method for characterizing the mechanical properties of thin films and small volumes. This dissertation reports the results of finite element analyses of elastic and elastic-plastic indentation by a rigid cone aimed at improving methods for measuring of contact area, hardness and elastic modulus by nanoindentation methods. Analytical and finite element results are presented which show that corrections to Sneddon's solution are needed to properly describe elastic indentation by a cone. Since most nanoindentation methods are based on Sneddon's solution, these corrections have important consequences for making accurate mechanical property measurements. Elastic-plastic finite element simulations are presented which show that pile-up can significantly affect the accuracy of nanoindentation measurements. It is shown that an experimentally measurable parameter, the ratio of the final depth to the total depth of indentation, is useful in determining the amount of pile-up in the material. An investigation of plastic zones and stresses in indented materials reveals important correlations between them and the nanoindentation behavior of the material. Implications of these results for indentation cracking are also discussed. A long standing problem in nanoindentation is why load-displacement data obtained during unloading fit well to a power relation with a power law exponents in the range 1.25-1.50. Finite element simulations combined with elastic contact analyses are presented which provide a simple explanation for this behavior. General recommendations are made for improving of nanoindentation methods for measuring mechanical properties.

The unsteady two-dimensional boundary layer equations are solved through the use of proper similarity variables and asymptotic techniques. The equations lend themselves to the derivation of similarity variables which ultimately transform the equations to a nonlinear partial differential equation (PDE). Asymptotic perturbation techniques reduce the PDE to a set of coupled ordinary differential equations. The zeroth order equation is solved for its behavior close to the plate and far from the plate using a Taylor Expansion and asymptotic analysis respectively. The first order equation is solved at each limit asymptotically. The resulting equations are matched to solve for the constants generated from each solution. Interestingly, comparison of well established numerical results reveals a reasonable degree of accuracy when the constants from the zeroth order equations are modified with the small corrective constants generated from the first order equations.

A method of producing, collecting, and measuring drop size distributions in liquid-liquid emulsions has been developed. The emulsion is produced in a standardized cylindrical mixing tank. Dispersed phase droplets are encapsulated with a thin polymer film through a polycondensation reaction. Once encapsulated, the droplets behave as solid particles and may be removed from the mixing tank and measured. Data collected in the laboratory is used to support a proposed second law function, which may be used to test the validity of correlations that predict drop size distributions in emulsions.

The effect of a nearby plane boundary on vortex shedding from a circular cylinder is investigated for laminar flow. A two-dimensional finite difference numerical technique is used to solve the incompressible Navier-Stokes equations in primitive variable form on a computational mesh that is generated using a body-fitted coordinate transformation. Results are first presented for flows at Reynolds numbers of 80 and 100, based on the cylinder diameter, with the cylinder constrained against movement. Several cases of moving cylinder simulation are also presented for flow at a Reynolds number of 100. Fixed cylinder cases were run initially at both Reynolds numbers for an unbounded cylinder to confirm agreement of the simulation results with experimental evidence. The influence of a nearby plane boundary was investigated through a traverse of gap ratios beginning with a value of 3.0 and concluding with 0.5. Additional attention was focused on the behavior of the flow at gap ratios in the vicinity of the vortex shedding suppression gap ratio. Nearing the plate, a maximum Strouhal period was observed for each flow as suppression was approached. Features of the more viscous flow at the lower Reynolds number occurred at larger gap ratios than for the higher Reynolds number, as expected. The moving cylinder simulations were conducted primarily to demonstrate the capability of the simulator to accommodate the moving boundary of the cylinder. Initial gap ratios were chosen for examination based on the behavior of the fixed cylinder in the vicinity of the gap associated with vortex suppression.

A conformal grid generation scheme has been developed and is automated in a general purpose code which can be used for the generation of computational grids for complex geometries. The code uses the repetitive application of a general analytical mapping function known as the Karman-Trefftz equation. This program can generate highly orthogonal grids having virtually any internal structure desired by the user. The only input attributes required by the program are the body coordinates of the shape, the orthogonality requirement of the grid, and information concerning the physical structure of the grid. Computational grids generated by this program are especially well suited for the numerical computation of supersonic flow fields.

The nucleation and growth of zinc vapor in converging nozzles are modeled. The temperature, pressure, velocity and growth distributions along the nozzle are calculated. The size distributions of the exiting particles are plotted. The results of nozzles with different initial pressures and different lengths (different nozzle half angles) are compared. The validity of Quasi-One Dimensional Approximation related to velocity and temperature distributions is discussed. This nucleation process is also experimentally studied with the nozzle of linearly varying cross sections at different initial vapor temperatures. The produced final metallic particles are examined by SEM (Scanning Electron Microscopy) and the size distributions are obtained. It shows that the experimental results corroborate the theoretical predictions.

Beside our arms, it is our hands that help us to perform tasks. At first glance, we seems to move our arms and use our hands naturally. On closer inspection, however, we find that both our arms and hands are redundant mechanisms which explains why our arms can approach an object using different postures and our hands can grasp the object with many feasible grasp configurations. Duplicating this phenomenon has led to many innovative designs of redundant arms as well as multifingered hands, and has sparked many useful analyses of these topics. This thesis presents a new approach to intelligent multifingered grasping and redundant arm manipulation. Methods proposed in this research yield a computationally efficient and physically meaningful model for the planning of grasp positions, the determination of squeezing finger forces and the visualization of the motions of redundant arms. Principles and concepts embedded in this analysis will help researchers to gain new insights toward better designs for hands and arms. The model developed in this thesis also provides mathematical justification for some of the motions of human arms and fingers. The main thrust of this analysis of multifingered grasping is the use of mechanical equivalent force/moment systems. These systems allow us to decompose each finger force into a normal and a tangential component. Using this decomposition of finger forces, we can visualize the contribution of each finger force by the resultant force and moment required to manipulate a grasped object. Additionally, the nature of this decomposition, which is one of the unique feature of our method, will allow intelligent utilization of touch sensors. The frictional constraints and the squeezing internal finger forces are elegantly taken into account through a computationally efficient algorithm for choosing grasp points. Our methods have also been extended into the grasp of solid objects. The second part of this thesis provides an efficient method for analyzing the inverse kinematic problem of redundant manipulators. Our method is based on fully using the directional properties of the columns of the Jacobian matrix which relates the joint velocities of the arm and the end effector velocities. Motions of a redundant manipulator are analyzed through its upper arm's motion and wrist's motion and the Jacobian matrix is partitioned accordingly. It is shown that the motion of the upper arm and the wrist can be evaluated separately and in parallel though this vectorized approach.

Ballistic limit curves are determined by using experimental and theoretical results for the permanent deformation of a plate subjected to an impact load. The experiments have been performed on shielded plates of various thicknesses and materials at the Hypervelocity Impact Research Laboratory of NASA JSC. Comparison of the theoretical and experimental deformations allows one to determine the dynamic yield strength of the plate material. It is assumed that the shields can be replaced by a single equivalent shield, and that the debris cloud produced by the impact expands according to the theory of Swift. A strain criterion is imposed and ballistic limit equations describing the critical projectile radius and the critical backwall thickness are derived. The corresponding curves are plotted for the case of the most damaging impact conditions. Comparison is made with empirical limit curves that are available in the literature.