In fluid mechanics theory, we recognize the presence of fluid flow conditions that tend to adhere to solid walls, also known as the no-slip condition.
This condition causes the velocity gradient around the surface to have specific patterns determining several parameters like shear stress, convection coefficients, and others, forming a layer with a specific thickness known as the boundary layer.
Typically, this layer is very thin, requiring a significant amount of mesh if we were to create mesh sizes around this layer equivalent to the boundary layer’s thickness.
One method to accommodate this boundary layer thickness without altering the entire mesh size in detail is inflation. It involves creating layered mesh along the normal direction to the wall surface, as illustrated in Figure 3.7.
Figure 3.7. Mesh inflation layer around an object
Since this mesh only extends in the normal direction from the surface (in mathematical terms, upwards from a coordinate system, typically the Y-axis), it’s commonly referred to as the positive Y-direction or the inflation direction, or y+.
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