Temperature Spectra from a Turbulent Free Thermal Plume and in Interaction with its Material Environment

In this work we study the interaction of an axysymmetric thermal plume with a thermosiphon flow that surrounds it. The thermal plume is created by a circular disk heated by joule effect at constant temperature. The disk is placed at an open ended vertical cylinder on a quiet constant temperature. The internal wall of the cylinder heats up under the effect of thermal radiation emitted by the hot source. The confinement of the fluid causes, in the bottom part of the cylinder, an aspiration of the fresh air. It is a thermosiphon flow that comes to interact with the plume. By studying the average and fluctuating thermal fields it was found that the flow of the plume is strongly influenced by the presence of nearby walls. It was noted that the vertical transport becomes more intense and the structure of the flow becomes more turbulent. On the other hand, we attend a fast homogenization of the flow in the upper cylinder. To obtain more detailed information of this flow, we develops, during this study, a spectral analysis of the fluctuating thermal fields for the case of a plume evolving in unlimited and in an enclosed environment. The energy spectra study shows an important shift of the energy peaks toward the high frequencies under the effect of the thermosiphon. As destroying structures them on a big scale generated by the plume, the thermosiphon provokes a fast mixture of the fluid thus while leading to vortex of weaker size.

کلیدواژه ها:

Axysymmetric thermal plume ، Confinement ، Turbulent structure ، Power spectral density ، Cascade concept of Kolmogorov