# Overview of Mesh Controls

Mesh controls are used to control the size and characteristics of the mesh in different areas of the model.

Controls are typically applied on geometric entities (volumes, surfaces, edges, points) but may also be applied to non-geometric entities (zone mesh attributes, extrusions, and so on).

The mesh size controls available vary by entity type. However, a number of common options are available for most types. These common options are summarized below:
• Absolute: Enter an absolute value that will be used to set the size of the elements.
• Relative: The size is computed as a function of the size of the bounding box that contains each geometric entity within the group. Note that the length scale of each entity is evaluated independently. So, using this option for a surface or volume group that contains multiple entities will result in different sized mesh on each component.
• Absolute Aniso: Enter an absolute size and a tensor that defines the orientation of the anisotropy. Note that the tensor must define three orthogonal vectors.
• Relative Aniso: Enter a relative size and a tensor that defines the orientation of the anisotropy. The size is evaluated, then multiplied by the longest edge length of the bounding box of the geometric entity to determine the final size. Note that the tensor must define three orthogonal vectors.
• Absolute Expression: Enter an expression to specify the absolute mesh size. The expression can be a function of x,y,z and must adhere to the expression syntax detailed in the appendix.
• Relative Expression: Enter an expression to specify the relative mesh size. The expression can be a function of x,y,z and must adhere to the expression syntax detailed in the appendix. The size is evaluated, then multiplied by the longest edge length of the bounding box of the geometric entity to determine the final size.
• None: This setting tells the mesher to apply no mesh controls to the entity. Note that the entity may still inherit mesh controls from a parent entity or from the global level.
• Curvature Refinement Parameters: Toggling this option on allows the mesher to automatically reduce the local mesh size to better resolve curved surfaces.
• Curvature Angle: This angle defines how many degrees of curvature a single element edge can span.
• Curvature Mesh Size Factor: This factor determines how far the mesher can reduce the mesh size that has been specified to meet the curvature angle criteria. The mesher will reduce the mesh size to a minimum limit that is equal to the mesh size specified on the entity multiplied by this factor.