The O-grid creation capability is simply the modification of a single block or blocks to a 5 sub-block topology (7 sub-blocks in 3D) as shown below. It arranges grid lines into an “O” shape to reduce skew where a block corner lies on a continuous curve or surface. There are several variations of the basic O-grid generation technique.
As shown below, the O-grid can be created with or without face selection.
Figure 23 O-grid Creation With and Without Face Selection
a) Circular Cylinder
b) Block Inside Cylinder
c) O-grid created without face selection
d) O-grid created with face selection
O-grids can be created or removed by selecting or deselecting Blocks, Faces, Edges, and Vertices. The following options are also available.
If toggled ON, the O-grid will be created outside the block(s).
Specify the height of the O-grid layer.
If toggled ON, the value assigned for Offset is the actual length of the radial edge of an O-grid. Assigning a Offset of 7 would make all the radial edges of the O-grid 7 units in length.
When Absolute is toggled OFF, Offset behaves like a relative distance: A value of 1 causes the Hexa Mesher to place the O-grid at a location where the resulting blocks will be distorted the least. A higher value makes the inner blocks of the O-grid smaller, with the surrounding blocks larger, and a smaller value makes the inner blocks larger and the surrounding blocks smaller.