### 23.3.2. Advanced Options Tab

It is possible to specify some further parameters to control the adaption process, these are specified on the Advanced Options tab of the Mesh Adaption form.

#### 23.3.2.1. Node Alloc. Parameter

Setting the node allocation parameter, Node Alloc. Parameter, controls how much the mesh is refined at each adaption step. For some problems, it may be that it is better to refine a lot in the early steps, and for others it may be more appropriate to refine more in the later steps.

Node Alloc. Parameter is used as follows. On the nth adaption step, approximately Sn nodes are added to the mesh, where

M is the maximum number of nodes that can be added to the original mesh calculated from having applied the Adaption Criteria to the selected regions and c is the value of Node Alloc. Parameter. For details, see Adaption Criteria.

When Node Alloc. Parameter is set to 0, then the same number of nodes is added for each adaption step. When Node Alloc. Parameter is negative, more nodes are added in the later adaption steps. When it is positive, more nodes are added in the earlier adaption steps. The table below shows the percentage of nodes that will be added at each adaption step when Max. Num. Steps is set to a value of 3 and different values of Node Alloc. Parameter are specified.

Node Alloc. Parameter | Step 1 | Step 2 | Step 3
--- | --- | --- | ---
-2.0 | 7.14 | 28.57 | 64.28
-1.0 | 16.66 | 33.33 | 50.00
0.0 | 33.33 | 33.33 | 33.33
0.5 | 43.77 | 30.95 | 25.27
1.0 | 54.54 | 27.27 | 18.18
2.0 | 73.47 | 18.36 | 8.16

It is recommended that you set a value for Node Alloc. Parameter in the range -2 to 2.

#### 23.3.2.2. Number of Levels

The value of this parameter specifies the maximum number of times any element of the original mesh can be subdivided. It must not be greater than Max. Num. Steps.

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