This thesis presents the results of an experimental investigation of the hydrodynamic characteristics of the Monoform hull in calm water. The forces acting on a 1.7 meter model were measured as the model was held captive and towed in calm water. The model was tested at speeds up to three meters per second. The rudders were held straight during one part of the study and were deflected during another to test both their ability to correct for pitching moment and to create yaw moments. The draft of the model was also varied during this study and included drafts of 1.90, 2.21, and 2.42 hull diameters. All three forces and all three moments were measured. The model was tested in a 31 meter towing basin located at Virginia Polytechnic Institute and State University. The results are presented in Figure form in the thesis body and in numerical form in an appendix. Recommendations for future work and improvements to the instrumentation are presented along with conclusions at the end of the thesis. / M.S.

The present work addresses the usefulness of a simple and efficient computer program (ULTSTR) for a sensitivity analysis of ship longitudinal strength, where this program was originally developed for calculating the collapse moment. Since the program is efficient it can be used to obtain ultimate strength variability for various values of parameters which affects the longitudinal strength, viz., yield. stress, Young's modulus, thickness, initial imperfections, breadth, depth, etc. The results obtained with this approach are in good agreement with those obtained by use of a more complex nonlinear finite element program USAS, developed by American Bureau of Shipping. / Master of Science

The influence of layer waviness in thick cross-ply composite cylinders subjected to hydrostatic pressure is investigated. The cylinders considered are graphite-epoxy with a 2: 1 ratio of circumferential to axial layers. All cylinders considered contain 104 total layers with a layup of [90/(90/0/90h71s, where a '0° 1 layer is taken to be in the axial direction. The influence of a single isolated group of wavy layers in an otherwise perfect cylinder is evaluated. Layer waviness in only the circumferential direction is considered, and the analysis is assumed to be valid only away from the cylinder ends. A parametric investigation is performed to determine the combined influence of wave location, wave amplitude, and cylinder geometry on hydrostatic response of the cylinder, particularly the stresses generated in and around the wave. The wave is assumed to be located either at the inner or the outer radius of the cylinder. Three wave amplitudes, 0, are considered: 1/2, 1, and 2 layer thicknesses. Only waves with a half wave length of 10 layer thicknesses are considered. Three cylinder geometries are considered, specifically ones with radius to thickness ratios of 5, 10, and 20. Finite element analysis is used to determine the stress state within the imperfect, i.e., wave included, cylinders. Based on a maximum stress failure criterion, failure pressures are determined for each of the various wave and cylinder geometries. Failure pressures for the imperfect cylinders are compared with those for a perfect cylinder to determine the failure pressure reduction ratios due to fiber waviness. It is shown that pressure capacity reductions of approximately 50% are possible for the range of parameters studied. Failure is primarily due to fiber compression, though interlaminar shear and interlaminar tension are a factor. Finite element analysis is also used to deter ine the failure pressure of the perfect cylinder due to buckling. This is done to determine whether failure due to buckling may overshadow material failure due to fiber waviness. It is shown that buckling is a factor in only one of the cylinder geometries considered, and only in the cases of mild layer waviness. In addition to results, details about the finite element model are presented. These details include geometry of the wave, changes in material properties due to local fiber rotation and local volume fraction changes, boundary conditions, and justifications for modeling simplifications that were made in an effort to reduce computational costs and analysis times. / Master of Science

Hydrodynamics and heat transfer characteristics found in fluidization were studied in a small scale laboratory fluidized bed. Experiments were designed to capture field data on multiple slit jet gas distributor systems for the validation of computational models. Localized data was quantified through the use of several novel non-intrusive experimental measurement techniques. The analyses provide a unique study that connects full field-of-view multiphase flow dynamics with transient heat transfer distributions. The gas-solid hydrodynamics were captured through three non-invasive measurement techniques, viz. Particle Image Velocimetry (PIV), Digital Image Analysis (DIA), and pressure drop spectral analysis. The effects of inlet gas flowrate, Geldart B and D classified particle types, and the number inlet gas slit jets were investigated. Frequency analysis of a differential pressure signal resulted in the classification of four difference flow regimes. The coupling of PIV with DIA captured particle velocity, solid circulation rates, average cycle times, dead zone sizes, jet merging effects, gas void fraction distributions, and maximum expanded bed heights. The heat transfer in fluidized and spouted beds containing a heated inlet gas source was studied through transient heat transfer measurements and analyses. Innovative experimental procedures were introduced to quantify bed-to-wall and gas-to-particle heat transfer characteristics. Two techniques were developed to overcome the spatial, time varying, and instrumental intrusive limitations often found in multiphase flow heat transfer studies. Infrared thermography was utilized along with derived discrete differential equations, and an inverse heat conduction analysis to solve for transient localized heat flux profiles and heat transfer coefficient distributions. As a result new data containing increased spatial resolution is presented on gas, wall, and particle temporal maps. Computations based from the thermal gradients quantified bed-to-wall heat flux profiles, gas-to-particle heat transfer coefficients, and localized rates of energy stored. / Master of Science

The thesis consists of two parts. The first part discusses the initial value problem of a fifth-order Korteweg-de Vries type of equation w_t + w_xxx - w_xxxxx - ⁿ&#8721;_j=1 a_jw^jw_x = 0, w(x, 0) = w₀(x) posed on a periodic domain x &#8712; [0, 2&#960;] with boundary conditions w_ix(0, t) = w_ix(2&#960;, t), i = 0, 2, 3, 4 and an L²-stabilizing feedback control law w_x(2&#960;, t) = &#945;w_x(0, t) + (1 - &#945;)w_xxx(0; t) where n is a fixed positive integer, a_j, j = 1, 2, ... n, &#945; are real constants, and |&#945;| < 1. It is shown that for w₀(x) &#8712; H¹_&#945;(0, 2&#960;) with the boundary conditions described above, the problem is locally well-posed for w &#8712; C([0, T]; H¹_&#945;(0, 2&#960;)) with a conserved volume of w, [w] = &#8747;^2&#960;₀ w(x, t)dx. Moreover, the solution with small initial condition exists globally and approaches to [w₀(x)]/(2&#960;) as t &#8594; + &#8734;. The second part concerns wave motions on water in a rectangular basin with a wave generator mounted on a side wall. The linear governing equations are used and it is assumed that the surface tension on the free surface is not zero. Two types of generators are considered, flexible and rigid. For the flexible case, it is shown that the system is exactly controllable. For the rigid case, the system is not exactly controllable in a finite-time interval. However, it is approximately controllable. The stability problem of the system with the rigid generator controlled by a static feedback is also studied and it is proved that the system is strongly stable for this case. / Ph. D.

This work presents a partitioned approach to simulating free-surface flow interaction with hyper-elastic structures in which a smoothed particle hydrodynamics (SPH) solver is coupled with a finite-element (FEM) solver. SPH is a mesh-free, Lagrangian numerical technique frequently employed to study physical phenomena involving large deformations, such as fragmentation or breaking waves. As a mesh-free Lagrangian method, SPH makes an attractive alternative to traditional grid-based methods for modeling free-surface flows and/or problems with rapid deformations where frequent re-meshing and additional free-surface tracking algorithms are non-trivial. This work continues and extends the earlier coupled 2D SPH-FEM approach of Yang et al. [1,2] by linking a double-precision GPU implementation of a 3D weakly compressible SPH formulation [3] with the open source finite element software Code_Aster [4]. Using this approach, the fluid domain is evolved on the GPU, while the CPU updates the structural domain. Finally, the partitioned solutions are coupled using a traditional staggered algorithm. / Ph. D.

A mathematical model was developed for the rapid filling of an initially dry pipe. The pipe was assumed to be horizontal and to contain an orifice at the downstream end. The key elements of the model were the momentum equation governing the flow of the water, the thermodynamic equations for the compression and discharge of the entrapped air, and the equations for waterhammer resulting from the impact of the water with the orifice. A computer program of this model was then developed and tested. After initial testing, the model was used to examine the magnitudes of the pressures that could be produced from waterhammer and air compression for various lengths of pipe. The effects that different orifice diameters had on the flow were also analyzed. The results indicated that extremely high pressures can be generated from both waterhammer and air compression during the filling process. These pressures tend to increase as the orifice diameter is reduced. However, below a certain size the orifice constricts the air discharge enough to stop the water prior to its reaching the orifice. This results in an oscillatory behavior of the flow, and the relation between waterhammer and orifice diameter becomes much more difficult to predict. The results also demonstrated that these pressures are significantly reduced for longer pipe lengths, and for pipes with smaller diameters or otherwise offering greater frictional resistance to the flow. / M.S.

A theoretical model and associated computer program are developed to compute hydrodynamic interaction forces and moments on passing ships in a shallow asymmetric canal, by applying generalized Lagally's theorem. Steady lift force on the ships are estimated following standard slenderbody approach. Passing ships are assumed to travel at constant speeds, parallel to the canal walls. Ships are assumed to be slender, the fluid is ideal and wave making effects are ignored. Numerical calculations for several passing cases show good agreement with existing model test results. / M.S.

Yes

Yes / An incompressible Smoothed Particle Hydrodynamics (SPH) method is put forward to simulate non-linear and dispersive solitary wave reflection and transmission characteristics after interacting with a partially immersed curtain-type breakwater. The Naviers¿Stokes equations in Lagrangian form are solved using a two-step split method. The method first integrates the velocity field in time without enforcing incompressibility. Then the resulting deviation of particle density is projected into a divergence-free space to satisfy incompressibility by solving a pressure Poisson equation. Basic SPH formulations are employed for the discretization of relevant gradient and divergence operators in the governing equations. The curtainwall and horizontal bottom are also numerically treated by fixed wall particles and the free surface of wave is tracked by particles with a lower density as compared with inner particles. The proposed SPH model is first verified by the test of a solitary wave with different amplitudes running against a vertical wall without opening underneath. Then it is applied to simulate solitary wave interacting with a partially immersed curtain wall with different immersion depths. The characteristics ofwave reflection, transmission, dissipation and impacting forces on the curtain breakwater are discussed based on computational results