Fluid Mechanics of Rough-wall Bounded Turbulent Flows

Real surfaces in engineering applications often deviate from the perfectly smooth surface in theoretical formulations. This has a sizeable impact on the performance outcomes, especially in extreme environments such as flow within a high-pressure compressor or turbine in a jet engine, or that over an aircraft wing, where the surface in contact with the fluid is subject to degradation in service. The effect of the 'roughening' of the surface on measures such as aerodynamic drag is poorly predicted by existing correlations, and the physical relationship not well understood. This project aims to shed light on the physics of flow perturbed by a rough surface, by finding a consistently measurable quantity that parameterises the roughness topography and its functional relationship to the resulting aerodynamic penalty. This will be achieved through scale-resolving Direct Numerical Simulations (DNS) to view the flow behaviour within the roughness cavities, the scale of these calculations made possible through GPU-parallelized code. The insights from these low levels of abstraction may be used to build new mathematical frameworks to describe the highly nonlinear system of turbulent flows with nondeterministic roughness. The ultimate goal is the ability to generate robust predictions of engineering relevance based on a generalized description of roughness.