The Eighth International Symposium on Physics of Fluids (ISPF8) was held in Xi’an, China, from June 10, 2019, to June 13, 2019. It attracted more than 200 researchers from around the world to present their research progress in the area of computational and experimental fluid mechanics and their applications. Many advances in the fundamental research of computational and experimental fluid mechanics and practical applications in the industry have been reported in the symposium. Specifically, the topics included turbulent flow, flow stability, flow visualization and measurement, fluid–structure interaction, aeroelastic analysis, supersonic and hypersonic flow analysis and experiments, multiphase flow, the lattice Boltzmann method and its applications, the immersed boundary method and its applications, and so on.
This special topic represents a selection of the papers presented in the symposium. It covers advances in the theoretical, experimental, and numerical studies of fluid mechanics. In their theoretical study, Kanso et al.1 explored the zero-shear and complex viscosities of different axisymmetric polymer configurations. They compared and contrasted the elastic and viscous components of the complex viscosities of macromolecular chains that are straight, branched, ringed, or star-branched. Tian et al.2 developed a vortex identification method by analyzing the physical meaning of the local rotation of fluid elements. Zheng et al.3 constructed an optimization framework based on the data-informed self-adaptive quasi-steady model. The framework aims to achieve a specific aerodynamic force coefficient by optimizing the kinematic parameters of the flapping motion of an ellipsoid wing. In their experimental study, Zou and Lee4 investigated the flow environment around rotor blades in a two-stage compressor via examining wake–blade and wake–wake interactions using particle image velocimetry. Their results provide striking examples of the complex flow and turbulence structures. On the topic of computational fluid dynamics, many new numerical approaches are developed, which provide efficient tools for the study of fluids physics. Chen et al.5 proposed an immersed boundary-simplified lattice Boltzmann method for the simulation of incompressible thermal flows with immersed objects. Liu et al.6 established a parallel fluid–structure interaction solver based on an immersed boundary-lattice Boltzmann flux solver and absolute nodal coordinate formula. Zhang et al.7 adopted an improved diffuse interface method to investigate the dynamics of bubbles and droplets moving in quiescent flows. Su et al.8 conducted high-resolution numerical simulations of the multi-component inert and reactive highly underexpanded jets to quantify the influences of the injected gas mixture properties on the flow structure. Tian et al.9 performed improved delayed detached eddy simulations to investigate aero-optical distortions induced by flow over a cylindrical turret with a flat window. Zhang et al.10 presented a numerical investigation of space–time correlations at two-point and two-time streamwise fluctuating velocities along the nozzle lipline. Yuan et al.11 investigated the skin-friction drag reduction of turbulent channel flow subjected to spanwise wall oscillation.
On behalf of the organizing committee, we wish to take this opportunity to thank each of the authors for their contribution to this special topic. We would like to thank Northwestern Polytechnical University, the Nanjing University of Aeronautics and Astronautics, Peking University, the National University of Singapore, the National Natural Science Foundation, and American Institute of Physics (AIP) for their sponsorship of this symposium. In particular, we wish to thank Professor Jeffrey Giacomin for his support of the symposium and this special topic in Physics of Fluids.