| The main objective of the thesis proposed herein is to develop a new 2-D ice model which is intended primarily for simulating the ice accretion process on transmission line cables. In an attempt to validate this new model, a number of experimental tests were carried out in the CIGELE icing wind tunnel, and the results obtained from these tests were then compared with those of numerical simulation.; The theoretical work is composed of two phases. In the first phase, the ice accretion process on a fixed cable was modeled, and model parameters, such as the Local Collision Efficiency (LCE) and the local Heat Transfer Coefficient (HTC), were evaluated based on time-dependent airflow and water droplet trajectory computations. For wet accumulations, the movement of a surface water film was tracked for each time step so as to obtain its direction of motion and thickness.; In the second phase, the ice accretion process on a rotating cable was specifically studied as an extension of the newly-developed ice code or model, while both gravitational and aerodynamic torques were considered in the rotation process. The aerodynamic forces were derived by integrating air pressure and air shear along the airflow boundary and were updated according to real-time airflow computations. Subsequently, this new model was applied to analyze two types of overhead transmission line cables under icing conditions, namely, the Bersimis cable and an overhead ground wire, and thereby a number of observations were made.; The conditions applied in the experimental tests in the icing wind tunnel are such that the effects of wind speed, size of test cylinder, air temperature and droplet Median Volume Diameter (MVD) may be revealed by the ice shapes, and that, furthermore, these ice shapes represent the range of the icing process from dry to wet accumulations. In particular, five sets of ice-shapes from both test results and model simulations were illustrated and compared within this thesis so as to validate the proposed ice model. It may be concluded from these comparisons that, in general, the ice shapes predicted by the proposed ice model are in satisfactory agreement with the shapes obtained from experimental tests. Nevertheless, this model tends to underestimate the ice-load to a great extent in the event that the air temperature is high, and the wet regime becomes dominant. In such a case, icicles form beneath the iced objects, and consequently if the weight of the icicles is disregarded, a considerable underestimation of the overall ice-load will occur.; In addition, this thesis examines the effects of Joule heating and water droplet size on the icing process using the new ice model. These effects, however, proved to be difficult to investigate with the experimental set-up currently available. By means of this new model, moreover, it also becomes easy to demonstrate the ice density distribution within the ice-accretion, as discussed in the latter portion of this thesis. |
