Adaptive Mesh Refinement (Transient)
Solver Start Simulation Adaptive mesh refinement, Properties
The adaptive mesh refinement properties dialog box allows you to change
the parameters used for the three-dimensional adaptive mesh refinement.
Please note that the adaptive mesh refinement is only active when the
corresponding button is checked in the transient solver control dialog
box.
The adaptive mesh refinement is an automatic scheme to create a mesh
better suited for the given problem. With the refined mesh a new calculation
pass will be started. Here, the initial mesh is automatically generated
by the expert system and is used for the first pass calculation. Afterwards,
the adaptive mesh refinement improves the mesh until the stop criteria
are satisfied.
As stop criteria, either the change in the S-parameters or the change
of a user defined 0D result template from one pass to the next are available.
For the refinement of the meshes, two different strategies are available:
The energy based mesh refinement stores the energy density distribution
within the structure during a calculation. Based on these data, the mesh
is refined afterwards in regions with high energy density. In contrast
to this, the strategy based on the expert system successively changes
the settings of the mesh expert system, so that finally an appropriate
mesh is obtained that can be used afterwards for further parameter studies
without activating the adaptive meshing again.
Number of passes frame
Minimum: This
is the minimum number of passes that will be performed. The mesh adaptation
will run for this minimum number of passes, even if the stop criteria
are already met. The minimum setting is 2 passes.
Maximum: This
setting determines the maximum number of passes to be performed for the
mesh adaptation. The mesh adaptation will stop after this maximum number
of passes, even if the stop criteria for the mesh adaptation have not
been met. This setting is useful to limit the total calculation time to
reasonable amounts. The minimum setting is 2 passes.
Adaptation stop criteria frame
Adapt to S-parameters:
Use the change in the S-parameters as stop criterion. The change in
the S-parameters has to be below a set threshold (Maximum
delta) for a number of consecutive passes (Number
of checks) for the stop criterion to be met.
The change in the S-parameters is determined
as the maximal deviation of the absolute value of the complex difference
of the S-parameters between two subsequent passes.
Keep in mind that a small shift in a pole location
may result in a strong change of the S-parameters at the pole’s
frequency and thus a large maximal deviation, especially in strongly resonant
structures.
This feature is only available if S-parameters
will be calculated.
Use full frequency
range: If activated, the full frequency range is used for the calculation
of the change in the S-parameters. If not activated, you can limit the
frequency range by setting the values in the Fmin / Fmax edit fields.
Fmin
/ Fmax: You can limit the frequency range used for the calculation
of the change in the S-parameters here.
Maximum delta:
This sets the threshold for the change in the S-parameters.
Number of checks:
This sets the number of consecutive passes for which the threshold for
the change in the S-parameters has to be below the set threshold for the
stop criterion to be met.
Adapt to 0D
result template: Use the relative change in a user defined 0D result
template as stop criterion. The relative change in the 0D result has to
be below a set threshold (Maximum relative delta) for a number of consecutive
passes (Number of checks) for the stop criterion to be met.
0D
result template name: Here you can select the 0D result template
to use as stop criterion. Only 0D result templates previously defined
in the template
based postprocessing dialog are available for selection.
Maximum
relative delta: This sets the threshold for the relative change
in the 0D result template.
Number
of checks: This sets the number of consecutive passes for which
the relative change in 0D result template has to be below the set threshold
for the stop criterion to be met.
Refinement settings frame
Refinement strategy
Determine here the strategy used for the adaptive
mesh refinement. Two different possibilities are available, either based
on the modification of the mesh expert system or determined by regions
of high field energy in the calculation domain.
Expert system based
Choosing this strategy, the mesh refinement
is performed by successively changing the settings of the mesh expert
system. This offers the possibility of running the mesh adaptation only
once to generate an appropriate mesh line distribution for the current
simulation model. This optimized mesh can be used afterwards for further
calculation runs with modified parameters (e.g., parameter sweeps or optimization
cycles) without activating the refinement process again.
Mesh
increment: This parameter determines the changing of the mesh expert
system by increasing the settings of Lines per wavelength and Lower
mesh limit in the Mesh
Properties dialog box.
Energy based
Choosing this strategy the mesh refinement is
based on the given energy distribution of the electromagnetic fields inside
the calculation domain.
Factor for mesh cell increase: This
factor determines how many new cells are introduced between two subsequent
passes of the mesh refinement. A setting of 0.5 means that 0.5 times more
mesh cells are used for the next calculation than have been used for the
previous one. In other words, the number of mesh cells increases about
50% from pass to pass.
Number of pulse widths to skip: The
behavior of a narrow bandwidth structure is often investigated within
a broader frequency band to keep the pulse lengths reasonably short. However,
in these cases a big part of the energy fed into the structure is reflected
almost immediately inside the device. Only a small part of the energy
remains in the structure and is used to investigate the device’s
behavior. However, because this small part is the actually important one,
it may be misleading if this energy is summed up with the large (but reflected)
part to determine the locations for the mesh refinement. In these cases,
the mesh refinement would lead to strange refinements in the feeding lines
without refining the critical parts inside the device. In such cases,
it is often useful to start the energy calculation after the reflected
energy has left the structure. Therefore, the number of pulse widths can
be specified after which the investigation of the energy will be started.
For narrow band structures, it is common to set this value up to 1-3.
On the other hand, the value should remain at zero for wide band structures.
Weight
for electric field energy: The electromagnetic field energy is
stored during the calculation and the mesh refinement is based upon the
energy density within the structure. However, sometimes a structure’s
behavior is more critically coupled to changes of the electric field than
to changes of the magnetic field. If this behavior is previously known,
it is useful to increase the weight of the electric energy compared to
the magnetic energy. By default, both electric and magnetic energies have
the same weights.
Weight
for magnetic field energy: As described above for the electric
energy weight, it is sometimes useful to increase or decrease the weight
for the magnetic field energy when it is previously known that the electric
or the magnetic field energy is more critical to the device’s performance.
Refinement
directions: If a button is checked, the mesh will be refined along
the corresponding coordinate direction. This option is useful to avoid
refining a mesh along coordinate directions in which the structure’s
fields have no dependency (e.g., some quasi-2D structures).
OK
Accepts
the changes and closes the dialog.
Defaults
Resets
all dialog parameters to the their default settings.
Cancel
Closes
this dialog box without performing any further action.
Help
Shows
this help text.
See also
Transient
Solver Properties
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