Abstract:
The frequency of
plume formation in fully-developed thermal convection
is determined experimentally.
Because the fluid has a temperature-dependent viscosity,
the cold and hot thermal boundary layers
have different thicknesses and viscosities. As a result,
plumes are released from these layers with different frequencies.
There appears to be a direct temporal
interaction between the cold
and hot boundary layers. In particular, whereas there is a single frequency
for cold plume formation, hot plumes form with multiple
frequencies, one of which is the
frequency of cold plumes.
The measurements thus suggest that
cold sinking ``plumes'' in the mantle can induce hot rising plumes.