The objective of the work described in this thesis is to evaluate the significance of the ambient fluid on the motion of an ice mass in the vicinity of an offshore structure and during the subsequent impact mechanism. Models for iceberg drift are first reviewed. The changes in flow field around an ice mass drifting in a current near an offshore structure are investigated by potential flow theory. The proximity effects and current interactions are generalized by introducing the added mass and convective force coefficients for the ice mass. A two-dimensional numerical model based on the boundary element method is developed to calculate these coefficients over a range of separation distances up to the point of contact. A numerical model based on ice properties and geometry is developed to simulate the impact force acting on the structure. Both the 'contact-point' added masses estimated in this thesis and the traditionally assumed far-field added masses are used in the impact model separately. The results from the two cases are compared and the crucial roles played by the ambient fluid during impact are discussed. Finally, a number of related topics is proposed for further studies. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

A series of laboratory experiments was conducted to examine the oscillatory forces" and the wave runup on a vertical, circular, surface piercing, rigid cylinder in the presence of both waves and a colinear current. It was found that a current which ran opposite to the direction of wave propagation reduced the oscillatory force and the runup on the cylinder. The results for a current running in the same direction as the waves were more scattered, with some cases indicating an increase in force while others a decrease. The runup, however, increased in all cases. An innovative numerical technique which is currently under development was applied to this problem. The loads on the cylinder were obtained by a time stepping procedure in which the flow at each time step was calculated by an integral equation method based on Green's theorem. The general results of the numerical method agreed quite well with the experimental observations, within the constraints of some simplifying assumptions. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Understanding asteroid collisions is a key part of Solar System science. To in- terpret observations of more than 100 asteroid families, various numerical sim- ulations are used. In this work, we prefer the smoothed particle hydrodynamics (SPH), which allows a detailed description of impact mechanics, shock wave propagation, fragmentation of the target, ejection, or reaccumulation controlled by self-gravity and secondary collisions. Since the respective time scale may reach the orbital time scale, the SPH is often complemented by efficient N-body integrators and collisional handlers. In the review part of the thesis, we describe details of numerical methods and their implementation in the new OpenSPH code. We also thoroughly test the code, using analytical solutions and labora- tory experiments as references, and discuss its stability and convergence with respect to spatial resolution. In the refereed papers, included in the thesis, we focus on collisions with targets of particular sizes (D = 10 and 100 km). We explore the dependence of outcomes on the target size, the projectile size, the impact speed, the impact angle, and most importantly, the initial spin rate. We demonstrate that rotation significantly decreases the effective strength of the targets and increases the ejected mass. We self-consistently...

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