It is well known that elastic or compliant boundaries can have a stabilizing effect on boundary layer flow leading to a reduction in turbulence and frictional drag. This phenomenon has wide-ranging interdisciplinary applications from the study of energy-efficient propulsion to the study of blood flow through the cardiovascular system. While a substantial body of work exists on the theory of turbulent boundary layers and the transition of laminar to turbulent flow, it is equally important to measure in detail the flow near rigid and compliant boundaries to better understand the dynamics underlying the stabilizing effect and the reduction of turbulence. Recent advances in technology and computational resources have allowed the measurement and numerical simulation of boundary layer instabilities in unprecedented detail. We employ particle image velocimetry as well as high-frequency fiber-optics sensors to visualize and measure velocity and temperature fluctuations under various flow conditions: a laminar flow tank to study the development of Tollmien-Schlichting waves and the laboratory tank of the Simulated Turbulence and Turbidity Environment (SiTTE) to identify boundary layers streaks. The laboratory environments are complemented by computational fluid dynamics representations of the respective setups, implemented as high-resolution large-eddy simulation. The simulations provide spatial and temporal scales of boundary layer instabilities, allow the calculation of turbulence characteristics and add prediction capabilities. The combined approach allows the detailed characterization of boundary layer instabilities for a range of flow conditions, which is critical to improve our understanding of the impact of elastic boundaries, both active and passive, on boundary layer drag.
Silvia Matt, Weilin Hou, and Wesley Goode, "Characterizing instabilities in the developed and transitional boundary layer," Proc. SPIE 10631, Ocean Sensing and Monitoring X, 106310I (Presented at SPIE Defense + Security: April 18, 2018; Published: 25 May 2018); https://doi.org/10.1117/12.2304377.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon