So how to calculate the First Cell Height for a desired Y+ value?įirstly, we should calculate the Reynolds number for our model based on the characteristic scales of our geometry such that: In some cases, we may need to locally refine our mesh to achieve the desired value in all regions. The computed flow-field will dictate the actual value which in reality will vary along the wall. Shear Stress Transport or k-epsilon with scalable wall functions)ĭuring the pre-processing stage, we need to estimate the first cell height ( ) so that our falls within the desired range. All turbulence models are applicable (e.g.Wall adjacent grid height should ideally reside in the log-law region where.This approach is suitable for cases where wall-bounded effects are secondary, or the flow undergoes geometry-induced separation (such as many bluff bodies and in modern automotive vehicle design). Involves modelling the boundary layer using a log-law wall function.Must use an appropriate low-Re number turbulence model (i.e.Wall adjacent grid height must be order.Involves the full resolution of the boundary layer and is required where wall-bounded effects are of high priority (adverse pressure gradients, aerodynamic drag, pressure drop, heat transfer, etc.).Let's review the two main choices we have in choosing a near-wall modelling strategy: This is an important first step as the global mesh resolution parameters will also be influenced by this near-wall mesh as well as the Reynolds number. Today we will help you calculate the correct first cell height ( ) based on your desired value. In previous posts we have stressed the importance of using an appropriate value in combination with a given turbulence modelling approach. Part 3 – Understanding impact of Y+ and number of prism layers on flow resolution.Part 2 – Resolving each region of the boundary layer.Part 1 – Understanding the physics of boundary layer s.The updated post series from 2020 is LEAP's 3-Part Series on "What y+ should I use in my simulations?" which is available here:
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |