Transient natural convection from vertically aligned horizontal fine wires in a still fluid

As a continuing study of transient natural convection from suddenly heated horizontal cylinder geometries, data is presented for single wire and two wire experiments that investigated the onset of convective motion, the approach to steady state as well as the steady state values of each arrangement. A Mach-Zehnder Interferometer was utilized in these experiments to provide optical measurements and results that when compared to the temperature responses, obtained by an unbalanced Wheatstone bridge assembly, provide the clearest physical picture yet of the development of the temperature field. The comparisons of the two wire results provide the first physical explanations for phenomena that had previously been observed but left unexplained.

Results presented here confirmed the existence of previously identified separate regimes in both experiments, and led to the identification of two new finite periods in the convective transition regime. The dependence of the temperature response on the heat input to the wire and the heat capacity ratio of the wire to the fluid was also confirmed and expanded. A physical explanation of the two wire scenario is presented and explains and correlates several previous studies that contradicted each other. Additional questions are also identified that may be answered by future experiments that have been streamlined by this study.