Invite Speaker I:
"Title:Acoustic metasurfaces for hypersonic boundary layer stabilization: mathematical modeling, design strategy, and mechanism"
Abstract
Hypersonic boundary layer (BL) transition generates a significant increase in viscous drag and heat flux, which leads to severe restrictions on the performance and thermal protection systems of hypersonic vehicles. Among various passive/active transition control strategies, acoustic metasurfaces demonstrate minimal effects on the mean flow but significantly suppress the Mack second mode. Therefore, it can be considered one of the most promising transition control technologies. Acoustic metasurfaces are planar metamaterial structures that comprise monolayer or multilayer stacks of subwavelength microstructures, which affect unstable modes via acoustic wave manipulations. This paper presents a review of the research progress made on acoustic metasurfaces for hypersonic BL stabilization. Acoustic characteristics and their corresponding stabilization effects on the first and second modes are compared and discussed. Recent improvements in the mathematical modeling of acoustic metasurfaces have been highlighted. The broadband design strategies and possible mechanisms are proposed and discussed.
Bio-Sketch
Dr. Rui Zhao is currently the Associate Professor of School of Aerospace Engineering, Beijing Institute of Technology. He received his Bachelor (2008) and Ph.D (2013) degrees in fluid dynamics from Beihang University. He was appointed as a visiting Assistant Professor at Hong Kong Polytechnic University in 2017. His research interests include hypersonic boundary-layer transition and control, ablation effect, thermal-chemical nonequilibrium, etc. He is now the Fellow of China Aerodynamics Society, and the youth editorial board member of Space: Science & Technology, Aerospace Technology, and Aerodynamic Research & Experiment. He has published two monographs and more than 40 academic papers in international journals. In 2023, he was awarded the Excellent Individual Awards of the First Exploration of Mars Mission of China.
Rui Zhao
Associate Professor of Beijing Institute of Technology, China
Invite Speaker II:
"Title:Designing of Supersonic Split Line Nozzles: Optimization, Mechanism, and Modeling"
Abstract
Thrust vector control systems are essential to modern rocket motors. They are widely used to ensure that rockets travel on their correct trajectories. The supersonic split line (SSSL) nozzle is one of the thrust vector nozzles. Because of the complex internal flow, designing a high-performance SSSL nozzle, especially with a large swing angle, could be quite challenging. In this talk, an SSSL nozzle design procedure is presented first. The multi-objective optimization method is utilized to determine the nozzle configurations that provide the best thrust vector performance. The influence of key geometric parameters on the nozzle thrust performance is uncovered. By monitoring the nozzle internal flow during the multi-objective optimization procedure, the significant roles played by shock waves on the nozzle thrust performance are demonstrated. Finally, a mathematical model is proposed to predict the thrust vector performance of the SSSL nozzles based on the resultant optimized nozzle configurations.
Bio-Sketch
Dr. Ben GUAN is now an Associate Professor at the College of Aerospace and Civil Engineering, Harbin Engineering University. He received his bachelor’s degree from Harbin Shangye University in 2008, master’s degree from Harbin Engineering University in 2012, PhD degree from the University of Science and Technology of China in 2016, and then acted as a Research Associate at the Hong Kong Polytechnic University until March 2019. His research covers solid rocket motor operational stability, advanced rocket nozzle, shock waves, Richtmyer-Meshkov instability, and droplet secondary breakup. He serves as a member of the Chinese Aerodynamics Research Society, and a member of the youth editorial board of Propulsion and Energy. He has published more than 20 academic journal papers
Ben Guan
Associate Professor of Harbin Engineering University, China
Invite Speaker III:
"Title:On the Low-Frequency Unsteadiness in Shock-Induced Separated Flow "
Abstract
Shock-wave/turbulent boundary-layer interactions feature a low-frequency, back-and-forth shock motion and large-scale flow structures. The physical mechanisms of these flow phenomena are revealed using linear stability analysis based on a separation of scales. For the first time, an intrinsic three-dimensional instability is identified, which manifests itself as corrugated separation and reattachment lines and pairs of counterrotating streamwise vortices downstream of reattachment. Shock-induced separated flow also responds actively to both two-dimensional and three-dimensional upstream disturbances as a consequence of modal resonance. For the former, the frequency-premultiplied optimal energy amplification peaks at a universal low frequency nondimensionalized using the length of the separation region and the freestream velocity. The response is in the form of a back-and-forth shock motion. For the latter, counterrotating streamwise vortices are excited and wander in the spanwise direction with a range of frequencies and spanwise wavelengths.
Bio-Sketch
Dr. Jiaao Hao is an Assistant Professor in the Department of Aeronautical and Aviation Engineering, the Hong Kong Polytechnic University. He received his PhD in Fluid Mechanics and BEng in Aircraft Design and Engineering from Beihang University in 2018 and 2013, respectively. His research interests include hypersonic aerodynamics, aerothermodynamics, and flow stability. He has published more than 40 papers in peer-reviewed journals, such as Journal of Fluid Mechanics, Physics of Fluids, Physical Review Fluids, etc.
Speakers in 2024 will be anounced soon.
Jiaao Hao
Assistant Professor of The Hong Kong Polytechnic University, China
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