Turbulent Boundary Layers over Heterogeneous Rough Surfaces

点击翻译按钮获取中文摘要

Turbulent flows over surfaces that have roughness variation in the streamwise direction are frequently encountered in nature (e.g. interfaces between ocean and landmasses, rural and urban areas, forest and grasslands) and in various engineering applications (e.g. turbine blades and ship hull due to bio-fouling or abrasive/corrosive effects) having a direct impact on aero/hydrodynamic performance and lifespan of fluid-flow systems as well as on dispersion of air pollution and wind patterns over urban areas. However, there is limited research in this field, hence the behaviour/prediction of turbulent flows and associated skin-friction drag development remain unclear over these types of rough surfaces. This study aims to fill this gap through cutting-edge experimental research with advanced laser-based optical flow diagnostics (i.e, PIV, PTV and DIC). We are particularly interested in resolving and predicting flow dynamics and associated skin-friction drag altered by a change in surface roughness (in the streamwise direction), as well as the interaction of a newly formed internal boundary layer (a shear layer) with the free surface. The latter is also important to understand and control transport mechanisms for CO2 and O2 (considering the severe and irreversible effects of global warming and the environmental targets for the next decades).