Beyond The Average: Computation of Vertical Profiles in Dilute
Pyroclastic Density Currents and Their Use in Shallow-Water Models
Abstract
Dilute pyroclastic density currents (PDCs) present significant hazards
due to their high temperatures and dynamic pressures. Accurate
estimation of dynamic pressure—- vital for assessing potential damage,
requires knowledge of the vertical variations of velocity and particle
concentration within the dilute PDC, particularly in the first few
meters of the flow. Existing approaches to dynamic pressure calculations
used in hazard assessment are often based on average values for velocity
and particle concentration. These average values may misrepresent the
flow dynamics, especially near the base of the flow where the gradients
of flow variables are larger. Here, we present a new, physically based
approach that allows for the calculation of the vertical profiles of
velocity and concentration from a combination of depth-averaged values
for these properties and non-dimensional flow parameters. Finally, we
demonstrate the use of these profiles within an existing shallow-water
model and show its potential applications toward probabilistic hazard
assessment.