OpenFOAM Chapter 4 (Section 7): Mesh Refinement Using a Grading Calculator (blockMesh + Reload) скачать в хорошем качестве

OpenFOAM Chapter 4 (Section 7): Mesh Refinement Using a Grading Calculator (blockMesh + Reload)

In OpenFOAM Chapter 4 — Section 7, we stop guessing and refine the mesh properly using a BlockMesh grading calculator. The goal is simple and physical: ✅ small cells near the square cylinder (Δ ≈ 0.05) ✅ larger cells far away and downstream where gradients are weaker ✅ smooth transitions between connected blocks (no sudden jumps) The grading calculator (3 inputs) The tool needs only: Total Expansion Ratio (how cell size grows along a direction) Total Length (block length in that direction) Number of Cells (cells along that direction) It outputs the key results, especially: ✅ first cell size and last cell size Step-by-step mesh upgrade 1) Fix Block B0 in the X direction For B0, length = 5H → with H = 1, length = 5 Cells: 20 Uniform mesh would give Δ = 5/20 = 0.25 (too big) Target near the square: ✅ last cell ≈ 0.05 We tune the expansion ratio until the last cell matches (example outcome: ratio ~ 0.75) Then we apply the same X grading to the connected blocks that must match near the square (e.g., B0 with its neighbors), save, and re-run: ✅ blockMesh In ParaView: right-click → Reload Files verify the cells smoothly shrink toward the square 2) Fix Block B0 in the Y direction Same method in Y: length ≈ 5 cells ≈ 20 tune the ratio so refinement matches near the square corners Apply to blocks that share Y alignment with B0 (example: B0, B1, B2), then: Save → ✅ blockMesh → Reload in ParaView Result: ✅ smooth matching cell sizes near the square corners (no abrupt jumps) 3) Fix downstream blocks (wake region) in X direction Downstream blocks: B2, B4, B7 Length from square to outlet ≈ 20H → 20 Here the priority is different: ✅ first cell near the square ≈ 0.05 Cells can grow toward the outlet. So we: increase X cell count (example: 60) tune expansion ratio to hit the first-cell target (example: ratio ~ 20) Then: Save → ✅ blockMesh → Reload 4) Fix lower blocks in Y direction Lower blocks: B5, B6, B7 Goal: ✅ refine near the bottom corners of the square (first cell ≈ 0.05) Tune Y grading (example: ratio ~ 13), then: Save → ✅ blockMesh → Reload Final result: a clean, physics-based mesh By the end, the mesh has a clear CFD logic: Far from the cylinder: larger cells Near boundaries (inlet/outlet/top/bottom): larger cells (low gradients) Near the square cylinder: smaller refined cells (separation, vortices, strong gradients) With this refined mesh ready, we’re set to continue with the remaining solver setup for square-cylinder flow. #OpenFOAM #CFD #blockMesh #MeshRefinement #simpleGrading #SquareCylinder #ParaView