Turbulent flow over rough walls appears in a variety of engineering applications, for example in gas turbine engine’s blades and ice-deposited on airplane wings. While roughness deteriorates the performance of these manmade engineering machines, animals like sharks utilize their rough skin to modify the surrounding turbulent flows to their favour and thereby achieve energy efficient locomotion. In order to understand the fluid mechanics in either scenarios, it is essential to understand how the geometrical details of the roughness affects the surrounding turbulent flow. This project is focused on developing a deep understanding of the connection between roughness topography and the turbulent flow around them.
The major challenge of addressing this question is the multiscale geometrical nature of the problem: while the rough elements are of the size of micrometers, the typical size of the device is of meters. This makes it extremely difficult to perform physical experiments, while numerical simulations are prohibitively expensive. We circumvent this problem by deriving boundary conditions that contain dominant effects of rough elements on the fluid flow. Such a feature provides an efficient computational framework which helps us to simulate details of turbulent flows over rough surfaces without representing details of the roughness explicitly. This in turn opens up the possibility of studying complex roughness patterns that are encountered typically in the engineering applications and in natural surfaces.