Particle dynamics in a shock layer produced by a supersonic jet impinging on a plate

Abstract

Particle laden supersonic flows impinging on obstacles are important for both, erosion and deposition processes. In order to obtain an understanding of important mechanisms of such processes the present study aims to investigate the dynamics of individual particles in the shock layer formed by a supersonic two-phase jet impinging normally onto a plate. For this purpose the method of high-speed multiexposure visualization of flow fields was applied. The free jet studied was characterized by Mach numbers of 2.6-2.8 and stagnation temperatures of 300-500 K. The disperse phase consisted of solid particles of different densities (2700-7900 kg/m3) and sizes (10-100 ƒÝm). The particles were injected into the flow ahead of the nozzle throat. In the optical diagnostics a series of light pulses was produced by a semiconductor laser. The duration of single pulses was very short (100 ns-10 ƒÝs) and the interval between different pulses lies in the range of 100 ns ¡V 1 ms. Particles impinging on the plate can be reflected. Results relating to the influence of reflected particles on the characteristics of the shock structure formed ahead of the plate will be addressed. Furthermore, particle dynamics, in particular, the formation of a cloud of particles within the shock layer will be discussed and related to a particular deposition mode observed in a coating process.