Laser Doppler velocimeter measurements of boundary layer velocity and turbulent intensities in Mach 2.5 flow
In recent years, the interest in developing a high-speed civil transport has increased. This has led to an increase in research activity on compressible supersonic flows, in particular the boundary layer. The structure of subsonic boundary layers has been extensively documented using conditional sampling techniques which exploit the knowledge of both u and v velocities. Researchers using these techniques have been able to explore some of the complex three-dimensional motions which are responsible for Reynolds stress production and transport in the boundary layer. As interest in turbulent structure has grown to include supersonic flows, a need for simultaneous multicomponent velocity measurements in these flows has developed. The success of conditional analysis in determining the characteristics of coherent motions and structures in the boundary layer relies on accurate, simultaneous measurement of two instantaneous velocity components.
Prediction and control of transition in supersonic and hypersonic boundary layers
Computations for sharp cones, using the e N method with N=10, show that the first oblique Tollmien-Schlichting mode is responsible for transition at adiabatic wall conditions for freestream Mach numbers up to about 7. For cold walls, the two-dimensional second mode dominates the transition process at lower hypersonic Mach numbers due to the well-known destabilizing effect of cooling on the second mode
Concentrated solar energy in materials processing
Solar energy, which is available in abundant in nature, is least utilised. As per primary energy product, solar energy conversion can be of three different ways: solar fuels, solar electricity, and solar thermal systems. These three approaches are presently not being fully utilised. Concentrated solar energy (CSE) is an alternative to other types of energy for modifying the surfaces of metallic materials. Attempt has been made to overview the current status of CSE in materials processing technology. In this paper, applications of CSE through solar furnace and Fresnel lens for hardening, coatings, sintering, nitriding, synthesis and welding are discussed.