BibTeX
@ARTICLE{
Charpentier2005Aso,
doi = "10.1111/j.1365246X.2005.02541.x",
ad_area = "Geophysics",
ad_tools = "Odyssee",
ad_theotech = "Tangent",
author = "Charpentier, I. and Espindola, J.M.",
title = "A study of the entrainment function in models of {P}linian columns: characteristics
and calibration",
journal = "Geophysical Journal International",
year = "2005",
volume = "160",
number = "3",
pages = "11231130",
month = "mar",
abstract = "Many of the processes involved in volcanic eruptive columns may be described
through physical models based on conservation laws in which a physical parametrization called the
entrainment function plays an important role. The solution of inverse problems and the estimation of
the characteristics of ancient eruptions are among the purposes of these models that require a
better knowledge of the characteristics and properties of this function. The first part of the study
shows that the three usual shapes chosen for this function yield apparently the same behaviour of
the column. However, we prove that a piecewise constant shape may be unsuitable in optimization
processes based on gradient methods. It also turns out that the parameters defining the entrainment
function cannot be considered constant. In the second part of the paper, the unique parameter of the
remaining two functions is viewed as dependent on the boundary conditions and specified with respect
to them. A calibration of the entrainment function with respect to real data is achieved through a
power law established between column height and discharge, the latter being related to velocity,
radius and bulk density at the vent. According to a discussion on eruptive data, the construction of
a mathematical parametrization for epsilon, with respect to boundary conditions and the heights of
the vent and the tropopause, appears to be an unwarranted and difficult task since any new addition
to the observed data will definitely modify the power law. A 4D database covering the range of
boundary conditions usually found in Plinian eruptions, together with an interpolation operator, are
constructed in order to provide an approximated parameter for any set of boundary conditions in the
range considered. Numerical results with a database of dimension 9(4) show that the approximated
parameter allows one to recover column height very accurately.",
issn = "0956540X",
id = "Charpentier2005Aso"
}
