摘自Fluent Theory Guide（對RANS模型而言）：
High quality numerical results for the wall boundary layer will only be obtained if the overall resolution of the boundary layer is sufficient. This requirement is actually more important than achieving certain values. The minimum number of cells to cover a boundary layer accurately is around 10, but values of 20 are desirable. It should also be noted that an improvement of boundary layer resolution can often be achieved with moderate increase in numerical effort, as it requires only a mesh refinement in the wall-normal direction. The associated increase in accuracy is typically well worth the additional computing costs. For unstructured meshes, it is recommended that you generate prism layers near the wall with 10–20 or more layers for an accurate prediction of the wall boundary layers. The thickness of the prism layer should be designed to ensure that around 15 or more nodes are actually covering the boundary layer. This can be checked after a solution is obtained, by looking at the turbulent viscosity, which has a maximum in the middle of the boundary layer – this maximum gives an indication of the thickness of the boundary layer (twice the location of the maximum gives the boundary layer edge). It is essential that the prism layer is thicker than the boundary layer as otherwise there is a danger that the prism layer confines the growth of the boundary layer.
簡單翻譯：
想獲得高質量的邊界層數值結果，邊界層必須要有足夠的網格解析度。保證邊界層的模擬的精確性所需的邊界層網格數，需要看實際需求，而不是簡單的達到某一個特定的網格數就足夠，邊界層最少需要10層左右的網格，但通常需要20層。適當提升邊界層的網格解析度而獲得更精確的數值解是值得的，因為邊界層網格通常只在壁面法向加密，加密網格而引起的計算量的增加是適度的（moderate increase）。對非結構網格，壁面附近使用棱柱型網格時，建議在壁面生成10-20層，或者更多層的。棱柱層的厚度內要保證有15個左右甚至更多個節點（node）。
可以使用湍流黏性的分布來判斷邊界層內網格解析度是否足夠，湍流黏性通常在邊界層的“正中間”附近達到最大值，如果邊界層網格沒有覆蓋住湍流黏性最大值所在的位置的2倍厚度的地方，那么邊界層網格數是偏少的，它將會限制邊界層的發展。