EAGER: Novel Instrumentation for Extracting and Modeling of Flow Structure in Turbulent Boundary Layers

University Of Florida, Gainesville FL

Investigators

Abstract

Development of new, more efficient aerodynamic vehicles is a constantly ongoing process. There are many areas of improvement that can be targeted, including reduced drag, enhanced maneuverability, and reduced noise levels. Although there is a long track record of research in aerodynamics, many of the basic properties of fluid flows are not completely understood. For instance, how forces along the surface of a body in motion relate to velocity in the surrounding air. Part of the reason is a lack of proper tools for measuring these flow interactions, which limits the experiments that can be performed. This project looks to develop new tools for the measurement of the flow-generated friction in multiple directions such that they can be combined with existing tools that estimate flow velocity with an ultimate goal of generating comprehensive experimental models of the turbulent motions. Information revealed from these efforts will enhance understanding of fundamental turbulent flows, which can be generalized to other more complex interactions. Furthermore, broad advances in sensor technology can be used by other research groups in their future endeavors, enabling increases in the next generation of aerodynamic performance. A full understanding of the interplay between wall forces and freestream fluid velocity within turbulent flow fields remains elusive and its study requires new technologies. Specifically, the temporal relationship between fluctuating wall shear stress and large scale motion of coherent turbulent structures in a boundary layer, among others. A key limitation to experimental validation of various models is insufficient measurement instrumentation, especially in multi-dimensional flows. Microelectromechanical system (MEMS) based transducers are developed to address this gap, including extending wall shear stress measurement capabilities from single-axis to time-resolved vectors. Specifically, a dual-axis, differential capacitive floating element skin friction sensor possessing a hydraulically smooth package is proposed. The novel sensor will provide the opportunity to sample the velocity field triggered by high-shear events allowing for greater insight into numerous open questions on turbulent boundary layers, including eddy formation, propagation, and the accuracy of the horseshoe vortex model. It will also provide the ability to make time-resolved vector measurements of wall shear stress at the microscale, which does not currently exist. Development of the novel MEMS sensors will continue to expand on the growing suite of transducers tailored for fluid applications, leading to instrument grade tools for aerodynamicists to utilize elsewhere.