Intermittent heat instabilities in an air plume

Autor: Jean-Louis Le Mouël, Pierre Morat, Frédéric Perrier, Vladimir Kossobokov
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Nonlinear Processes in Geophysics, Vol 23, Iss 4, Pp 319-330 (2016)
ISSN: 1607-7946
Popis: We report the results of heating experiments carried in an abandoned limestone quarry close to Paris, in an isolated room of a volume of about 400 m3. A heat source made of a metallic resistor of power 100 W was installed on the floor of the room, at distance from the walls. High quality temperature sensors, with a response time of 20 s, were fixed on a 2-m long bar. In a series of 24-hour heating experiments the bar had been set up horizontally at different heights or vertically along the axis of the plume to record changes in temperature distribution with a sampling time varying from 20 s to 2 min. When taken in averages over 24 hours, the temperatures present the classical shape of steady state plumes, as described by classical models. On the contrary, the temperature time series show a rich dynamic plume flow with intermittent trains of oscillations, spatially coherent, of large amplitudes and a period around 400 s, separated by intervals of relative quiescence whose duration can reach several hours. To our knowledge, no specific theory is available to explain this behavior, which appears to be chaotic interaction between a turbulent plume and a stratified environment. The observed behavior, with first order factorization of a smooth spatial function with a global temporal intermittent function, could be a universal feature of some turbulent plumes in geophysical environments.
Databáze: OpenAIRE
Externí odkaz: