Turbulent drag reduction by fibrous permeable substrates
Abstract
This project studies coatings made up of fibers aligned in the streamwise direction as a means to reduce turbulent skin friction. The fibers would constitute an anisotropically permeable substrate, which has recently been proposed as a drag-reducing, passive flow control technology. The idea is to exploit optimally the drag-beneficial mechanisms present in existing technologies, such as riblets, while minimizing the effect of drag-adverse mechanisms, to obtain a more robust performance. Preliminary work suggests that the present technology could outperform riblets by at least a factor of two, with drag reductions of order 20–25% at laboratory Reynolds numbers. Previous work has characterized the macroscopic properties of the substrate when the pore scale is vanishingly small, providing the tools to propose optimal fibre layouts and estimate their performance. To continue this effort, this project will study such configuration in realistic flow conditions. For this we will conduct a set of direct numerical simulations of turbulent channels coated by fibrous substrates, where all the time and length scales are fully resolved. We will use these to identify and characterize the key dynamical mechanisms, with the objective of producing simplified models that allow for fast yet accurate engineering calculations.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 21, 2022
- Source ID
- FA86552217062XX0
Entities
People
- Ricardo Garcia-Mayoral
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Cambridge