Recently, the doctoral dissertation of Luoqin Liu of the State Key Laboratory for Turbulence and Complex Systems (LTCS) was published in Springer.
Dr. Luoqin Liu received his bachelor's degree in Thermal Energy and Power Engineering from the Department of Thermal Science and Energy Engineering, University of Science and Technology of China in 2011. After then he was enrolled in the Department of Mechanics and Engineering Science, Peking University to pursue his doctoral degree in Fluid Mechanics. Under the guidance of Professor Jiezhi Wu, Weidong Su and Yipeng Shi, he worked on the force theories of aerodynamics, which is of significant theoretical significance and application value. The related research results have been published in top academic journals such as JFM and POF. His thesis "Unified Theoretical Foundations of Lift and Dragin Viscous and Compressible External Flows" was selected as the excellent doctoral dissertation of Peking University. After graduation in 2016, Dr. Liu joined the research group of Professor Xian-Tu He, Center for Applied Physics and Technology, Peking University, working on hydrodynamic instabilities and compressible turbulence. In the same year, he was awarded the Boya Postdoctoral Fellowship of Peking University.
Aiming at developing modern theoretical aerodynamics based on exactly the same Navier-Stokes equations as used in computational fluid dynamics (CFD) for viscous and compressible external flows, the doctoral thesis of Luoqin Liu consists of three innovative breakthroughs by both far-field and near-field approaches:
(1) A universal zonal structure of aerodynamic far field, in which all disturbance flow quantities must decay exponentially if and only if the flow is unsteady and compressible. Three commonly used simplified flow models, being inviscid, steady, or incompressible, only work in their respective true subspaces of the free space;
(2) A universal and exact total-force formula as direct extension of and with the same form as the classic lift and drag formulas, along with its far-field asymptotics in terms of physically testable variables;
(3) A general near-field theory for aerodynamic force and moment, steady or unsteady, which permits detailed complex-flow diagnosis including the Mach-number dependence of every physical constituents of flow structures. The predictions of these theories are confirmed by numerical tests. These findings fill some long-standing significant gaps of theoretical aerodynamics. Combined with CFD, they provide a unified foundation for future development of modern aerodynamics.