hello and welcome
this lesson is part two of the two-part
series on performing shared topology in
ansys flow and meshing watertight
geometric workflow and will focus on the
interface connect method
we will dig into the final details of
the method and understand how and when
to use it
let's get started
[Music]
the alternative to the joint intersect
share topology method discussed in part
one of this lesson
is the interface connect method
this method can be used to achieve
increased robustness and speed of share
topology operation
when there are matching overlapped
surfaces between bodies
matching here refers to the overlapping
surfaces having similar shape and
dimensions
the reason for this is that the method
is based on first stitching the edges of
the surfaces that overlap with each
other
and then removing one of the overlapping
surfaces
note that the method can also be used
for fixing non-matching overlapped
surfaces
in order to use this method efficiently
it is recommended to create labels or
named selections or the overlapping
surfaces at the cad creation level
though the method also works when no
labels are defined
when using ansys spaceclaim to prepare
the cad
labels can be defined on surfaces in
multiple ways
let's quickly look at how this can be
done
we will be using the geometry shown here
for our demo
the standard way of creating labels is
to select the appropriate geometrical
feature and selecting create an s from
the group step
when the cad is loaded into ansys flow
and meshing
these name selections are imported as
labels
notice that the two cylinders are
connected to two rectangular surfaces on
both sides
as discussed earlier
the interface connect method works best
when overlapping surfaces are of similar
shape and dimension
we need to split the rectangular surface
to create two circular regions where the
cylinders are connected
for this
we can use the imprint feature from the
prepared tab
when this option is selected
space line automatically detects
coincident faces edges or vertices
and imprints them onto the connected
geometry
here
we see that the four circular edges of
the cylinders are highlighted when the
imprint option is selected
click on the green arrow to implement
the imprint operation
we can now see that the rectangular
surfaces have been split into circular
surfaces
where the cylinders are connected to it
now
create the named selections for the
overlapping faces
once these are created
let us now load this model into ansys
fluent in machine
here is ansys fluent in meshing mode
with watertight geometry workflow
selected
in the import geometry task
leave all other options to default and
read the geometry file
we will not be adding any local sizing
and will create the surface mesh default
settings for this demo
if we now look at one of the overlapping
pairs
we can clearly see the overlapping mesh
which needs to be fixed
ansys fluent automatically adds the
apply share topology task to the
workflow after the surface mesh is
created
if it detects that a multi-body part has
been imported without any shared
topology
before moving to the apply share
topology task the describe geometry task
needs to be executed
here
since we have only the solid regions
we will select the first option for the
geometry tab
we will leave all the other options to
default and click describe geometry
in the apply share topology task
let us now select the interface connect
method for the share topology method
there are three ways to select surfaces
to implement this share topology method
which can be chosen from the interface
labels selection method setting under
advanced options
when named selections have been defined
for the overlapping surfaces at the cad
level
the default label selection method is
the manual method
here
simply select all the surfaces in this
case eight surfaces that overlap with
each other and hit apply share topology
the meshing algorithm will first stitch
the overlapping surfaces
and then remove one of the surfaces and
remesh locally to create a conformal
mesh in the interface as we see here if
the labels need to be maintained for the
boundary condition specification or for
post-processing purposes
it is recommended to set
rename internals based on body names
setting to no
for details on other advanced options
please refer to the user guide
for most cases
the default values for these settings
are sufficient
the other method that can be used to
select the overlap surfaces is the
automatic method
as the name suggests the overlapping
surfaces are automatically identified by
the meshing algorithm and hence no
manual user selection is required
this is helpful when no labels are
defined
however
because the algorithm has to brute force
identify the overlapping surfaces
there is virtually no speed up that is
attained when using this method
when compared to the default join
intersect share topology method
let us now go back to spaceclaim to
discuss another method of creating named
selections
here we have the same model as before
with imprint operation already performed
but with no name selections defined
now
we will use the force share option from
the workbench tab to automatically
define the named selections
when this option is selected
spaceline performs a contact check
between the bodies
and highlights them in the graphics
window
if we turn on the only create contact
groups option in the options for the
four share operation
and select the green tick mark to
complete the operation
spaceclaim will only create named
selections for overlapping surfaces
but does not perform share topology
the name selections will have a naming
convention that starts with connect
topology
followed by a number
the number of named selections created
depends on the number of contacts in the
model
in our case we have four contacts
and hence four named selections
note that each named selection contains
both the overlapping surfaces
let's now import this geometry into
watertight workflow and perform the same
steps as earlier till describe geometry
task
in the apply share topology task
the default share topology method is
automatically set to interface connect
this is because the meshing algorithm
automatically identified overlapping
surfaces
based on the labels created when the
force share operation was performed in
space lane
if we now look at label selection method
under advanced options it is set to
automatic using connect topology
no manual label selection is required
leave rename internals based on body
names option to yes to rename the
surfaces based on body weights
select apply share topology to perform
the shared topology operation
and create a conformal mesh between the
connected bodies
when using the interface connect share
topology method it is recommended to set
the ignore proximity across objects
option to yes while generating the
surface
this forces fluent meshing to ignore any
small gaps between adjacent bodies
typically applicable in cases where
there are duplicate faces or edges
between different bodies
turning on this option improves the
performance of the interface connect
method
let's summarize what we learnt in this
lesson
in cases where shared topology cannot be
performed at the cal creation phase
it is possible to do this operation at
the meshing phase when using the
watertight geometry workflow through the
apply share topology task
in this lesson we looked at the
interface connect method to perform
share topology between different bodies
we learnt about the functioning of the
method and the requirement of labeling
the overlapping or connected surfaces at
the cad creation level to improve the
robustness and speed of the interface
connect share topology operation
with that let's wrap up this video
you