Basics of lava-lamp convection

Abstract

Laboratory experiments are reported in an immiscible two-fluid system, where thermal convection is initiated by heating at the bottom and cooling at the top. The lava-lamp regime is characterized by a robust periodic exchange process where warm blobs rise from the bottom, attach to the top surface for a while, then cold blobs sink down again. Immiscibility allows to reach real steady (dynamical equilibrium) states which can be sustained for several days. Two modes of lava-lamp convection could be identified by recording and evaluating temperature time series at the bottom and at the top of the container: a "slow" mode is determined by an effective heat transport speed at a given temperature gradient, while a second mode of constant periodicity is viscosity limited. Contrasting of laboratory and geophysical observations yields the conclusion that the frequently suggested lava-lamp analogy fails for the accepted models of mantle convection.

An ∼60-Million-Year Periodicity Is Common to Marine87Sr/86Sr, Fossil Biodiversity, and Large-Scale Sedimentation: What Does the Periodicity Reflect?

“…Since the 87 Sr/ 86 Sr signal is a global one, presumably a globally synchronized periodicity in mantle convection would be required-an idea which finds some support in the observations of Mjelde and Faleide (2009) that there has been a synchronization between Iceland and Hawaii. Gyüre and Jánosi (2009) show that whole-mantle convection (rather than isolated up-and downwellings) with a period of a few tens of millions of years is the expected behavior.…”

Gravitational instabilities in binary granular materials

“…The Rayleigh-Taylor (RT) instability (13) is a classic fluid mechanical phenomenon in which lighter fluid pushes into denser fluid above it due to buoyancy, producing "fingers" and "bubbles" of lighter fluid. This instability manifests itself in a broad range of systems, from the formation of mushroom-shaped clouds in nuclear explosions (14) to fingering patterns in supernova explosions (14) to structures in lava lamps (15). A variety of fingering patterns (16)(17)(18) have been observed in grains, including densitydriven, RT-like phenomena when a closed cell containing liquid (19) or gas (20) and particles is quickly inverted and the fluid pushes upward on the falling particles.…”