With the rapid progress of computer performance, CFD made remarkable progress and became an important tool for analysis and design in both academic study and industrial engineering. Most of practical simulations had to use so-called RANS models with the restriction of computer resource. Turbulence research with more sophisticated models, on the other hand, stayed in simple geometries under relatively low Reynolds number flow conditions. The story is now changing and high fidelity simulations with LES are becoming used even in practical applications of industries. Computer progress is one of the reasons, but, more importantly, approaches that can inherently capture nonlinear and stiff nature of fluid phenomena are becoming needed.
Flow separation control has been one of the important research topics in fluid dynamics. Among many types of flow control, strong interest lies on the control of flow separation over an airfoil at high angles of attack. Recent micro and small devices such as synthetic jets or DBD plasma actuators have been shown to be very effective for the control of flow separation over an airfoil.
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After flashing back 30 years of CFD with HPC and a short discussion of aero-acoustic applications (Fig. 1), mechanism of flow separation control by DBD plasma actuators is discussed based on a series of computations of low speed flows over airfoils will be mainly discussed. The device is shown to be very effective for controlling flow separation (Figs. 2 (a), 2(b)). Strong authority of this device is strongly related to the turbulent transition but the study reveals that that is not only the factor. The study at cruise condition also shows better aerodynamic performance than that of a well-designed airfoil. Currently, experimental effort for practical applications are in progress with some industries, which may show its effectiveness for wide applications. Fluid behavior in a very small region both in time and space may totally change global flow structures and aerodynamic performance. As a part of the summary, the author would like to discuss why we need large-scale (high-order accurate) LES simulations even in the preliminary stage of future aerodynamic design process.
Bio sketch
Dr. Kozo Fujii is a Professor of Tokyo University of Science in Japan since March 2015. He was a professor of Institute of Space and Astronautical Science, (ISAS/JAXA) until he joined the university. After receiving his Ph. D. from University of Tokyo in 1980 and spending several years at NASA Ames R. C. and others, he came back to the ISAS and work there for about 30 years. He has been working on CFD for more than 40 years since early days of CFD in aerospace. His research interests include variety of studies on aerodynamics, but recently focus mainly on aero-acoustics and flow control. He lead a sub-project of “Industrial Innovation Program” on K supercomputer and now leads one of the new Challenging Issue programs for Post-K supercomputer in Japan. He gave numbers of invited keynote lectures such as ones in 7th ICCFD in 2012, 4th ICJWSF in 2013 and Parallel CFD in 2015. One typical example of many awards he received is “Daniel & Florence Guggenheim Award” from the ICAS in 2004. He has been a Fellow of AIAA since 2004. He serves as a vice chair of the HPCI committee for future policy of HPCI in Japan. He is currently a council member of Science Council of Japan.