Expansion of a Modified Transient Liquid Crystal Method for Thin Plates of Different Materials

The purpose of this research is to apply a modified transient liquid crystal method to a thin flat plate to determine the local temperature distribution and heat transfer coefficient. This research examines three different plates: 1) 1/8 inch thick Plexiglas plate, 2) 1/2 inch thick Plexiglas plate, and 3) 1/8 inch thick aluminum plate. Each plate is approximately 6 inches in length by 3 inches in width. The temperature distributions on a flat plate are viewed over time using a liquid crystal thermography (LCT) technique. The plates are coated with a wide band liquid crystal (R30C5W) and fixed in a vertically oriented wind tunnel. For any thickness plate, the speed of the tunnel was adjusted for a Reynolds number within the range of approximately 22100 and 23100. For the theoretical analysis, the thin flat plate used a convective surface boundary condition and a 2-D transient finite-differencing conduction scheme. An initial local heat transfer coefficient distribution is selected based upon flat plate theory and is used to calculate an initial streamwise temperature distribution. The local heat transfer coefficient distribution is readjusted until the theoretical temperature distribution matches the experimental temperature distribution over the center surface of the plate. This technique allows a wider application of transient LCT and for heat transfer coefficients to be mapped on thin surfaces of different materials.

USE OF RECIPROCITY THEOREM FOR COMPUTATION OF LOW‐FREQUENCY RADIATION PATTERNS

Starting with a simple word statement of the reciprocity which exists between forces and displacements in a general elastic solid, it is shown that low‐frequency radiation of shear and compressional waves from relatively complex sources can be obtained by solving relatively simple problems in static elasticity. Illustrative examples include radiation from radial and tangential pairs of forces acting on the wall of a cylinder, pressure in a finite cylinder, and a pair of radial forces in a hole in a plate. For the last case, measurements in a plexiglas plate compare favorably with computations.