Flow over rough surfaces, and conjugate heat transfer, in engineering applications

Abstract: This thesis focuses on two important topics in the field of fluid mechanics and heat transfer that were treated separately. On the one hand, the flow over rough surfaces, which is not yet completely understood, despite of the fact that it has an important implication in many engineering applications, especially in the naval industry for ships and boats because the friction drag caused by fouling, antifouling coatings and roughness in general impacts the fuel consumption and toxic emissions to the atmosphere. In this thesis, new ways to measure and predict the friction drag of rough surfaces are presented, using both numerical simulations and experimental techniques. On the other hand, conjugate heat transfer processes are also important in many applications, but a very relevant one is the electric generators for hydropower, since there is a current need of increasing the efficiency of these machines, which depends a lot on how they are cooled and therefore, on the rate at which the heat that is generated during their operation is dissipated (transferred to the cooling fluid). In this thesis, an experimental method for studying the heat transfer in these machines is presented and validated. Also, new correlations to improve the design phase of the electric generators are also evaluated.