Examples of cellular materials include spongy bone, plant stems and leaves, as well as aquatic corals. Natural cellular materials are often multi-functional and demonstrate unique physical properties such as low density, high strength and stiffness, and the ability to regulate fluid flow. Due to advances in additive manufacturing technology, it is now possible to create such multi-functional materials for engineering applications. This project aims to develop porous cellular materials for passive flow control. Appropriately designed porous materials have the potential to reduce flow-induced noise, decrease skin friction, regulate heat transfer, and control separated or high-speed flows. The resulting performance improvements could benefit aircraft, waterborne vessels, and ground vehicles. The research effort described below will clarify the fundamental flow physics that underpin these applications and generate scientific tools that can aid the design of cellular materials for flow control. The project also has several educational and outreach components, including sustained undergraduate research involvement, support for capstone senior design projects, and long-term collaboration with a local high-needs public school.
The research will focus on gaining a better understanding of turbulent boundary layer flow over a porous substrate. The control objective will be to suppress the near-wall turbulence to ultimately reduce skin friction (i.e. drag). This research involves three key objectives. First, reduced-complexity models will be developed to predict how porous materials with specified bulk properties (e.g., porosity and permeability) modify the near-wall turbulent flow. The models will be used to optimize the bulk properties to suppress near-wall turbulence. These results will then be used to design and fabricate (via 3D-printing) cellular materials exhibiting bulk properties identified by the models. This component will bridge macroscopic descriptions of natural cellular materials with the design of actual manufacturable cell geometries. Finally, channel and boundary layer experiments with the porous cellular-like material walls will be used to measure the statistical and structural features of the turbulent flow. In addition to providing insight into turbulent flow physics over complex anisotropic porous materials, these experiments will serve as proof-of-concept validation for the models. Together, these research activities will create a tightly coupled theoretical and experimental framework that can guide the development of cellular materials with desired macroscopic properties to control a variety of turbulent flows.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
