Recent Research Progress on the Mechanism, Modelling, and Algorithm of Two-phase Interfacial Flow and Reacting Flow under Extreme Conditions

The Spray Combustion and Propulsion (SCP) Laboratory, which is affiliated with Tsinghua University, is dedicated to the cutting-edge research of two-phase flow and chemically reactive flow under ultra-speed, strongly compressible, and high transient conditions, and the SCP Laboratory applies fundamental research conclusions to solve key technique issues in aerospace power and propulsion area. Recent research progress of SCP Laboratory on fluid mechanism, modelling, and algorithm of two-phase interfacial flow and chemically reactive flow under extreme conditions was summarized. At first, the analytical model and high-precision numerical method of the strongly compressible two-phase interfacial flow with a high transient phase transition process were introduced. Then the unsteady shock wave propagation theory for the relationship of wave angle, wave intensity, and other physical quantities during the shock wave transmission and reflection processes with constraints of the two-phase planar/curved interface was introduced. Based on above model and method, a series of basic flow problems such as shock wave/droplet, high speed droplet/wall collision were studied, and the spatiotemporal evolutions of complex wave and interface system in high transient process were analysed. Taking the cavitation in the shocked droplet as an example, the mechanism of cavitation induced by convergent expansion waves at the curved interface was revealed and the theoretical formula was put forward to predict location of the cavitation core. Furthermore, the strongly compressible two-phase spray reactive flow in combustion chambers was introduced. The SCP Laboratory develops high performance numerical simulation software TURFsim, which is based on the Euler-Lagrange framework, and this software has been successfully applied in the simulation of aeroengine and supersonic combustion chamber with complex geometry. Taking a typical supersonic mixing layer simulation as an example, the physical mechanism of the oblique shock wave enhanced mixing was summarized. The propagation mode and mechanism of fire nuclei and flame propagation under extreme conditions were put forward. The spatiotemporal evolutions of sprays, wavelets, and local detonation waves were demonstrated. A quantitative combustion characterization method with the third Damköhler number Da_Ⅲ was proposed and this nondimensional parameter was applied on the identification and evolution analysis of local quasi-isochoric combustion process. The above research results play an important role on the understanding of complex physical processes and engineering design of aerospace engines.