Development of miniaturized sensor array for measuring pressure and shear stress distributions in turbulent wall flows with flexible nanometer thin-film mirrors in polymer
Abstract
Accurately measuring wall (pressure & shear) stresses with sufficient spatial andtemporal resolutions (e.g. ~50um & ~10us) has ove rarching implications in fundamental research and navy-relevant applications, such as complex turbulent flow-wall interactions and a dvanced flow control strategies for drag management nologies (e.g. oil film interferometry, pressure sensitive paint) are limited to applications in air, existing MEMS stress sensors b ased on piezoelectric materials result in costly and bulky sensors with limited frequency responses and low measurement sensitivitie s that fail to resolve pressure & shear fluctuations in high Re flows, the inherent flow regimes to many naval applications. Enabled by our success in synthesizing the wrinkle-free nanometer metallic thin film encased in polymer (WiMTiP), we propose to develop a d istributed sensor technology that is capable of measuring non-intrusively and simultaneouslypressure and shear stress distributions over a submerged surface at high spatial resolutions (e.g.50) and rapid response frequency (e.g. >100 kHz) with high sensitivit y (e.g. < 40 Pa). To achieve such capabilities, we will create an array of WiMTiP composite filled uWells (e.g.5050100um, the late st being the depth) in a solid substrate with only their top surfaces open to flows. The nm-scale 3D deformations within each uWell, caused by its interactions with local stresses, is obtained by measuring directly the deformation of a flexible thin film mirror (e .g.50nm) embedded horizontally within each uWell through a reflective digital holographic microscopic interferometry (DHMI).In this project, based on our WiMTiP (patent-pending) technology we will develop themicrofabrication techniques allowing syntheses of sens ors and non-intrusive optical readout(DHMI) methodology enabling measurements of nm pressure-/shear-induced deformations. A proto type containing a mosaic of WiMTiP sensors with different sizes and shapes will be fabricated in both a Si wafer and a conformable p lastic (e.g. polyimide) substrate. The stress-strain relation of the sensor will be firstly measured microscopically by an Atomic Fo rce Microscope and quantified macroscopically in a benchtop hydrostatic testing chamber equipped with a DHMI. The relation will be f urther improved by developing a 3D Finite Element model. The developedprototypes will be applied to measure wall pressure and shear distributions in an adverse pressure gradient turbulent boundary layer. Results will be validated by pressure drop measurements and flow field assessment by Particle Image Velocimetry. Effects of uWell size, shape and viscoelasticity of bulk polymer will also be evaluated against measurement accuracy and response frequency. Prototypes of a densely packed 128128 sensor array in conjunction w ith DHMI techniques that translate nm sensor deformation to wall stresses, will be delivered in the end. Scientifically, the propose d measurement technique represents a paradigm shift technology andthe first-of-its-kind in measuring pressure and shear distributio ns. Technically, successfully synthesis of WiMTiP composite in confinement address technical challenges in fabricating polymeric fun ctional metamaterial, which may enable many naval related technologies such as distributed flexible sensor array for advanced feed-b ack flow control solutions for super-cavitating body, force-based battlefield awareness for underwater vehicles and substantially im prove war fighting capability.In this project, we will train 1 postdoc, 1 Ph.D. and 2 undergraduates, with preferences given to fem ale underrepresented minority students from south Texas.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 07, 2021
- Source ID
- N000142112834
Entities
People
- Jian Sheng
Organizations
- Office of Naval Research
- Texas A&M University–Corpus Christi
- United States Navy