Simulation and Modeling of Effects of Rough Walls on Non-equilibrium Turbulent Boundary Layers
Abstract
The aim of this project is to improve fundamental understanding of non-equilibrium turbulent flows close to rough surfaces, and develop physics-based, data-driven models of these flows, based on single-point turbulence closures. An extensive roughness-resolved, direct-numerical-simulation(DNS) database was established, that contains a wide range of equilibrium and non-equilibrium turbulent flows over rough walls with many different roughness geometries. This database was used to identify the role of roughness and its topography in modifying turbulent statistics and structures in equilibrium flows and non-equilibrium ones, including transient channels and boundary layers with non-zero longitudinal pressure gradients. In particular, results revealed the similarity of the roughness sublayer velocity profile in non-equilibrium flows, and highlighted the importance of form-induced velocities in affecting turbulence evolution in these flows. Based on physics inferred from the database, new representations of roughness in turbulence models were introduced and tested in equilibrium and selected non-equilibrium flows. Compared to existing roughness treatments in RANS closures, the new models offer advantages such as preserving the near-wall stress balance and the potential for describing near-wall flow in strongly adverse-pressure-gradient boundary layers. Frameworks for structure-based modeling of rough-wall flows were explored. By leveraging the extensive DNS database, machine-learning techniques were developed and employed to determine roughness-specific model coefficient values for RANS closures for computing attached boundary-layer flows over surfaces of almost arbitrary roughness.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 12, 2022
- Accession Number
- AD1180839
Entities
People
- G. J. Brereton
- Junlin Yuan
Organizations
- Michigan State University