Abstract
Density profile in a thin thermal boundary layer arising near a rapid-heated surface was measured by using an optical technique. A 2-mm diameter stainless tube in a room temperature air environment was employed as a test section. The developed switch circuit attained a constant power density of 0.4MW/m^2 after micro-risetime (8.6-μs). The local variation of density was estimated from the displacement of fringes generated by transmitting the object wave of Mach-Zehnder interferometer through thermal boundary layer. The experimental result indicates fair agreement with the unsteady thermal conductivity equation immediately after heating. However, the discrepancy responsible for the occurrence of convection was observed with increase in heating time.
