DNS of Pressure Fluctuations Induced by Supersonic Turbulent Boundary Layers

Lian Duan, Missouri University of Science and Technology

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Understanding the physics of the pressure fluctuations induced by turbulent boundary layers are of major theoretical and practical importance. From a practical point of view, the fluctuating pressure on aerodynamic surfaces of flight vehicles plays an important role in vibrational loading and often leads to damaging effects as fatigue and flutter. An in-depth knowledge of the nature of boundary-induced pressure fluctuations is thus essential to the structural design of launch vehicles and other important applications. The proposed work aims to use the computational power of the Blue Waters to provide the basis for an in-depth understanding of the global pressure field induced by turbulent boundary layers at supersonic speeds and the dependence of the fluctuating pressure field at different flow conditions. Such an understanding will advance the state of the art knowledge of wall-bounded turbulence and contribute to the modeling and control of wall-bounded turbulence. Additionally, the broader impact of the project will be to enable valuable energy savings of transport vehicles. Overcoming turbulent friction consumes a large fraction of the United States energy budget. In 2012, vehicles that transport people/goods on ground, air or water throughout the U.S. consumed more than a quarter of the annual energy expenditure to overcome turbulent friction. The study of wall-bounded turbulent flows will contribute to better vehicle designs and the deployment of advanced flow control techniques for transport vehicles. Furthermore, the research activities of the project fully integrates with an education and outreach programs to inspire and meet the ever-increasing educational demands of next-generation engineers.

The research objective of this project is to investigate the structure of the turbulent pressure field in compressible boundary layers. This will be achieved by carrying out high-Reynolds-number direct numerical simulations (DNS) of compressible turbulent boundary layers using Blue Waters. Many existing analysis of the boundary-layer-induced pressure fluctuations is based on the Poisson equation in the context of incompressible flows, but for supersonic flows the pressure field is governed by the acoustic wave equation and is significantly less understood. In this work, the PI will generate high-Reynolds-number DNS data of compressible turbulent boundary layers to fundamentally understand the non-local pressure-related coupling between different regions of the boundary layer. In particular, this work will focus on studying pressure statistics and their scaling and developing a high-fidelity understanding of the origin of the pressure fluctuations in various frequency/wave-number ranges.