1Geomagnetism, Institut de Physique du Globe de Paris, 1 rue Jussieu,
75238 Paris, CEDEX 05, France
2Institute of Earthquake Prediction Theory and Mathematical Geophysics,
Russian Academy of Sciences, 84/32 Profsoyuznaya Street, 117997 Moscow,
Received: 18 Mar 2016 – Discussion started: 30 Mar 2016
Abstract. We report the results of heating experiments carried out 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 h 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 to 120 s. When taken in averages over 24 h, 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 amplitude 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 a 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.
Revised: 06 Jul 2016 – Accepted: 18 Jul 2016 – Published: 30 Aug 2016
Le Mouël, J.-L., Kossobokov, V. G., Perrier, F., and Morat, P.: Intermittent heat instabilities in an air plume, Nonlin. Processes Geophys., 23, 319-330, doi:10.5194/npg-23-319-2016, 2016.