Block Format Keyword Defines the criteria for adaptive meshing in parts. This keyword is not available for SPMD computation.

## Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
Angle Criterion Inilev Thkerr
ID1 ID2

## Definitions

Field Contents SI Unit Example

(Integer, maximum 10 digits)

(Character, maximum 100 characters)

Angle Criterion Angle criterion for mesh refinement. 3

(Real)

$\left[\mathrm{deg}\right]$
Inilev Initial level of refinement.
>0
Elements of the corresponding parts are divided, at time 0, up to the level equal to Inilev.

(Integer)

Thkerr Criterion based upon estimated thickness error. 4

(Real)

$\left[\text{m}\right]$
ID1, ID2 IDs of parts declared for adaptive meshing within this set.

(Integer, maximum 10 per format)

1. Several sets of parts may be declared for adaptivity, each using for instance, different angle criteria.
2. A part declared for adaptivity can include 4-node shell elements or 3-node shell elements and use any shell element formulation; except DKT18 and DKT_S3 formulations for triangles.
3. The Angle Criterion (degrees) defines the maximum angle between two neighboring elements; if this angle is reached, elements will be subdivided.
The element normal is checked versus the averaged normal at nodes as:
• Element Normal is computed at the maximum level and normalized.
• Averaged normal at nodes are computed:
(1)
${N}_{i}=\sum _{e}\frac{{N}_{e}}{‖{N}_{e}‖}$
• Normal at nodes is normalized.
• For each active element that is not at maximum level, the angle between its normal and the normal at its nodes is computed; and if this angle is greater than the defined criterion, the element is divided.
4. If Thkerr > 0, a thickness error estimation is computed as follows:
Nodal thickness is computed as:(2)
$\overline{t}=\frac{\sum _{k}A\left({E}_{k}\left(n\right)\right)t\left({E}_{k}\left(n\right)\right)}{\sum _{k}A\left({E}_{k}\left(n\right)\right)}$

Where, $A\left({E}_{k}\left(n\right)\right)$ and $t\left({E}_{k}\left(n\right)\right)$ are the area and thickness of element ${E}_{k}\left(n\right)$ containing node $n$ .

Then the thickness error is evaluated for each element, $E$ using the formula:(3)
${e}_{t}=\frac{1}{{A}_{E}}\underset{{A}_{E}}{\int }|\frac{t-\overline{t}}{t}|$

If the thickness error is greater than the criterion Thkerr, the element is divided.

5. The Angle and thickness error criteria are only checked at frequency defined through "Time delay" format provided in /ADMESH/GLOBAL.
6. Criteria Angle criterion and Thkerr can be used separately or combined.
7. In Adaptive Meshing, Node ID and shell ID are limited to < 900000000.