When solving a fluid flow problem using computational fluid dynamics (CFD), high-resolution mesh is required near the wall boundaries to capture the flow behavior and property gradients in the boundary layer region. The Add Boundary Layers task in the Ansys Fluent Meshing Watertight Geometry Workflow allows you to define the boundary layer mesh in the computational model through a set of user inputs. In this lesson, we will discuss the ‘Add In’ and ‘Grow On’ user inputs, which are used to specify the regions and the surfaces (respectively) on which the user wants to create the boundary layer mesh. We will explore the influence of different ‘Grow On’ options on the boundary layer mesh generation. Finally, we will learn about the additional options under ‘Add In’, which provide the flexibility to select specific regions, including solid regions, to generate the boundary layer mesh.