Characteristics of the oblique detonation flow field induced by a complex wave structure

In this paper, the initiation characteristics of the oblique detonation flow field induced by single- and double-wedge surfaces of finite length in a confined space are investigated. Numerical simulations with a detailed H₂/air reaction and theoretical shock polar analyses are combined to study the influence mechanism of a complex wave system structure on the characteristics of the oblique detonation. The effects of expansion waves on the oblique detonation waves (ODWs) and their flow field characteristics for different equivalent ratios and geometric sizes are analyzed in single-wedge and double-wedge structures with the same inflow parameters. The results show that the length of the induced ODW is shorter in the double-wedge structure than in the single-wedge structure. For the single-wedge structure, the strength of the expansion wave increases, the wall temperature drops, and the characteristic length of the induction zone decreases with increasing deflection angle of the second wedge. If the strength of the expansion wave is sufficiently large, the ODW is initiated. For the double-wedge structure, the ODWs interact and form a complex wave system structure, consisting of a Mach stem, two reflected detonation waves and slip lines. The length and the temperature before and after the Mach stem decrease with an increase in the strength of the expansion waves. The effects of the expansion waves on the flow field of the ODW are relatively small at a large equivalent ratio and significantly larger at a small equivalent ratio.     

Interference of spherical wave of thermal radiation emitted by a film system

This paper deals with the interference of spherical waves of thermal radiation emitted by a surface film system which consists of a metal substrate and a semi-transparent film. A spectroscopic experiment is made to reconfirm the clear interference in emission spectra of the film system. We present a theoretical model in which an electromagnetic theory for a spherical wave is combined with Planck’s theory of thermal radiation. The mechanism of interference of spherical waves is discussed, and it is suggested that thermal radiation waves emitted by a number of dipoles of the metal might be coherent among each other.