Experimental Study of Turbulent Flow over Permeable Rough Surfaces
Abstract
A variety of turbulent flows are over surface that are rough and permeable. Evolution, engineering design, manufacturing constraints and natural phenomena lead to rough and permeable boundaries in these porous surfaces (e.g. flow in heat exchangers, forest and urban canopies, bird feathers and river beds). The permeability and the roughness of a porous surface alters the turbulent boundary layer that develops over it and consequently the wake past an object with surface porosity. This entirely depends on the interaction between the external flow in the boundary layer over the roughness or the wake and the flow field within the porous media. Despite the wide-ranging impact and relevance, there is a clear lack of fundamental understanding and the scaling laws that relate the properties of porous media to the features of external flow. In this project, we carried out a systematic study where we explored the coupling between roughness and porosity and their effects on turbulent boundary layer flows. We performed systematic wind tunnel experiments over permeable and rough surfaces in order to examine if the flow over such surfaces can be considered in the same framework as flow over rough surfaces. Data indicates that this is indeed possible and that we might be able to define a sand grain roughness associated with permeability and another that is associated with roughness. Together, these two definitions can be combined to make predictions on the drag incurred by preamble rough surfaces. We also examined the influence of permeability and roughness on the flow structure within the boundary layer. The combination of permeability and roughness have very counter inuititive effects on the flow structure.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 13, 2022
- Accession Number
- AD1192155
Entities
People
- Bharathram Ganapathisubramani
Organizations
- University of Southampton