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ANSYS FLUENT 12.0 Theory Guide - 15.8 Particle Erosion and Accretion Theory
15.8 Particle Erosion and Accretion Theory
Particle erosion and accretion rates can be monitored at wall boundaries. The erosion rate is defined as
(15.8-1)
where
is a function of particle diameter,
is a function of impact angle,
velocity, and
is the impact angle of the particle path with the wall face,
is the relative particle velocity,
is a function of relative particle
is the area of the cell face at the wall. Default values are
,
, and
.
Since
,
, and
are defined as boundary conditions at a wall, rather than properties of a material, the default
values are not updated to reflect the material being used. You will need to specify appropriate values at all walls.
Values of these functions for sand eroding both carbon steel and aluminum are given by Edwards et al. [ 86].
The erosion rate as calculated above is displayed in units of removed material/(area-time), i.e., mass flux, and
can therefore be changed accordingly to the defined units in ANSYS FLUENT. The functions
and have to
be specified in consistent units to build a dimensionless group with the relative particle velocity and its
exponent. To compute an erosion rate in terms of length/time (mm/year, for example) you can either define a
custom field function to divide the erosion rate by the density of the wall material or include this division in the
units for
and/or . Note that the units given by ANSYS FLUENT when displaying the erosion rate are no
longer valid in the latter case.
A variety of erosion models [ 97, 221, 85, 249, 126, 299] containing model constants [ 126, 85] and angle
functions can be easily implemented into ANSYS FLUENT. The equations describing some of the erosion
models can be modified to appear in the form of the general equation describing the erosion rate, Equation 15.81. For example, the Tulsa Angle Dependent Model [ 85] described by Equation 15.8-2
(15.8-2)
can be rewritten in the form of Equation 15.8-1 with the following substitutions:
=
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ANSYS FLUENT 12.0 Theory Guide - 15.8 Particle Erosion and Accretion Theory
=
where
is the erosion rate,
is the Brinell hardness, and
is a particle shape coefficient.
User-defined functions can be used to describe erosion models of any form. For more complex models, such as
those models with varying function angles,
, the default Erosion Model in the Wall boundary condition
dialog box cannot be used. Hence, a user-defined function should be used instead. For information on how to
apply user-defined functions for DPM erosion models, see this section in the separate UDF Manual , or contact
your support engineer for further assistance.
Note that the particle erosion and accretion rates can be displayed only when coupled calculations are enabled.
The accretion rate is defined as
(15.8-3)
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Up: 15. Discrete Phase
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