Published online by Cambridge University Press: 26 April 2007
We consider the exchange flow of relatively dense, viscous fluid in a container connected by a vertical pipe to a container beneath it, initially full of relatively light fluid. A non-dimensional value for the flux of dense fluid down the tube is determined experimentally as a function of the ratio of the two viscosities and the Reynolds number. The experimental data are satisfactorily collapsed using dimensional analysis and balancing buoyancy, inertial and viscous forces as appropriate. A theoretical analysis, assuming steady, axisymmetric motion, captures a considerable part, but not all of the processes involved. The paper discusses quantitative applications of the results to the movement of magma in volcanic conduits. The concepts indicate how bi-directional convection in the conduit between a lava lake and a magma reservoir deep in the crust is the essential ingredient in the explanation of the long-standing problem that the amount of degassing of sulphur dioxide from a lava lake in a volcanic crater can exceed by many orders of magnitude that consistent with the amount of lava solidified in the crater. Movies are available with the online version of the paper.
Movie 1. Water draining from a sealed cylinder of height 16.9cm and radius 7.9cm, through a tube of internal radius 0.55cm and length 100cm (not all in view). The emptying of the chamber passes through three distinct regimes, characterised by their accoustic signature as popping, glugging and slugging.
Movie 1. Water draining from a sealed cylinder of height 16.9cm and radius 7.9cm, through a tube of internal radius 0.55cm and length 100cm (not all in view). The emptying of the chamber passes through three distinct regimes, characterised by their accoustic signature as popping, glugging and slugging.
Movie 2. Bi-directional flow between an upper reservoir containing pure glycerine and a lower reservoir containg 65 wt.% glycerine, connected by a tube of internal radius 0.55cm and length 20cm, (gamma = 83, Re = 0.45).
Movie 2. Bi-directional flow between an upper reservoir containing pure glycerine and a lower reservoir containg 65 wt.% glycerine, connected by a tube of internal radius 0.55cm and length 20cm, (gamma = 83, Re = 0.45).
Movie 3. Bi-directional flow between an upper reservoir containing pure water and a lower reservoir containing corn oil, connected by a tube of internal radius 1.5cm and length 20cm, (gamma = 0.015, Re = 1700).
Movie 3. Bi-directional flow between an upper reservoir containing pure water and a lower reservoir containing corn oil, connected by a tube of internal radius 1.5cm and length 20cm, (gamma = 0.015, Re = 1700).
Movie 4. Bi-directional flow between an upper reservoir containing pure glycerine and a lower reservoir containing pure water, connected by a tube of internal radius 1.5cm and length 20cm, (gamma = 1000, Re = 3.7).
Movie 4. Bi-directional flow between an upper reservoir containing pure glycerine and a lower reservoir containing pure water, connected by a tube of internal radius 1.5cm and length 20cm, (gamma = 1000, Re = 3.7).