Wall roughness effects in turbulent flows using large-eddy simulation

Topic description

Hydraulic installations can operate outside their nominal range, leading to accelerated wear and more frequent maintenance needs. It is established that the roughness of waterway surfaces in turbines and pump-turbines have a significant impact on the safety, performance, and efficiency of hydraulic machines, particularly by altering the turbulent flow structure and increasing pressure losses.

The prediction of these losses typically relies on an equivalent roughness height, which are not enough acccurate. The effects of roughness can be fully resolved using numerical simulation, but this approach requires very significant computational resources. If one wishes to avoid using a mesh adapted to surface roughness, immersed boundary methods are a promising alternative, as they can handle complex geometries derived from scanned surfaces.

This thesis aims to contribute to the analysis of hydraulic flows near rough walls by performing hi...