OpenFOAM Chapter 4 (Section 6): Mesh Refinement in ParaView — Grading Toward the Square Cylinder скачать в хорошем качестве

OpenFOAM Chapter 4 (Section 6): Mesh Refinement in ParaView — Grading Toward the Square Cylinder

In OpenFOAM Chapter 4 — Section 6, we move beyond “mesh created” and start doing what real CFD work requires: ✅ Inspect the mesh carefully — then refine and improve it. We already generated a basic mesh for the square-cylinder case. Now we open it in ParaView, identify where the mesh is too coarse, and begin refining strategically (not randomly). What you’ll do in this section 1) Inspect the mesh in ParaView Run paraFoam → click Apply Change: Surface → Surface With Edges Zoom in near the square cylinder and identify the blocks (B0, B1, B2, …) 2) Why refinement is needed (square cylinder physics) Two common CFD mesh problems: Large jumps in cell size between neighboring regions Mesh too coarse where gradients are strong In this case, we expect near the square cylinder corners: flow separation strong velocity gradients strong pressure gradients ✅ So we need smaller cells near the cylinder, especially at the corners. 3) First improvement target: Block B0 grading Goal: As Block B0 approaches the square, the last cell size should match the neighboring refined region. We compute the target cell size near the square: Square side length = 1 Cells along that length = 20 ✅ Target: Δ = 1/20 = 0.05 So we want the last cell in Block B0 to become 0.05, ideally in both: X-direction Y-direction 4) How to compute grading Two practical options: Option A — Use grading formulas Use the standard relationships between: total length (L) number of cells (N) expansion ratio (R / alpha) first/last cell sizes Option B — Use a grading calculator (faster) Search: blockMesh grading calculator A common reference is the OpenFOAM wiki script: “blockMesh grading calculation” Use it to tune simpleGrading until the last cell matches 0.05 Next steps In the next section, we’ll apply the same grading/refinement logic to other blocks and corners, step by step, until the mesh is suitable for accurate CFD around the square cylinder.