At the surface of the object, the flow becomes slower and the velocity distribution (boundary layer) is generated according to the distance from the surface. Layered meshes should be created on the surface of the object to reproduce the effect of this flow velocity distribution.
Set layer thickness ratio and number of layers at "Layer mesh settings" on "Mesh" page. Layer thickness ratio is a ratio to volume mesh. For example, if you want to set thickness of 5 layers to a volume mesh, set "0.2 (= 1/5)" as the layer thickness ratio.
Push
button to add a layer mesh setting. If you delete the setting, push at upper-rigt corner of the setting (blue rectangle).