""" validate_cube.py -- dedicated phase-1 validation mesh. Goal: reproduce the paper's static-cube validation cd ~= 0.935 (bracketed by the unbounded cube-particle correlations Hoelzer 0.854 / Haider-Levenspiel 1.122). That benchmark needs a LOW-BLOCKAGE, FACE-FORWARD, axis-aligned cube -- NOT the high-blockage 45-deg diamond of the production dataset. Geometry: unit cube [-0.5,0.5]^3, face normal to the +x inflow (frontal area = c^2, matching the paper's Aref = c^2). Large box (+/-8c laterally, 8c up / 16c down) => blockage < 1%. Cube is finite in z (free stream above/below), like production. Mesh: 3x3 transfinite block grid in x-y around the central square, extruded in 3 z-bands (planes at z = +/-0.5). Axis-aligned => zero-skew pure hex. The central column's mid z-band is tagged 'cube'; subsetMesh carves it out (same pipeline as the production mesh). """ import os, gmsh # ---- domain / cube --------------------------------------------------------- X = [-8.0, -0.5, 0.5, 16.0] # x partition lines (cube faces at -0.5, 0.5) Y = [-8.0, -0.5, 0.5, 8.0] # y partition lines zc, z_far = 0.5, 8.0 # cube half-height ; outer z extent # transfinite node counts per segment (upstream, central, downstream) Nx = [22, 28, 28] Ny = [20, 28, 20] cx = [0.86, 1.0, 1.16] # progression: <1 fine at end, >1 fine at start cy = [0.86, 1.0, 1.16] nz_mid, nz_band, z_ratio = 28, 20, 1.16 gmsh.initialize() gmsh.option.setNumber("General.Terminal", 1) geo = gmsh.model.geo z0 = -z_far # 4x4 grid of points at z0 P = [[geo.addPoint(X[i], Y[j], z0) for j in range(4)] for i in range(4)] # horizontal lines H[i][j]: from P[i][j] to P[i+1][j] (x-direction, segment i) H = [[geo.addLine(P[i][j], P[i+1][j]) for j in range(4)] for i in range(3)] # vertical lines V[i][j]: from P[i][j] to P[i][j+1] (y-direction, segment j) V = [[geo.addLine(P[i][j], P[i][j+1]) for j in range(3)] for i in range(4)] # 9 surfaces S = [[0]*3 for _ in range(3)] for i in range(3): for j in range(3): cl = geo.addCurveLoop([H[i][j], V[i+1][j], -H[i][j+1], -V[i][j]]) S[i][j] = geo.addPlaneSurface([cl]) # transfinite curves for i in range(3): for j in range(4): if cx[i] == 1.0: geo.mesh.setTransfiniteCurve(H[i][j], Nx[i]) else: geo.mesh.setTransfiniteCurve(H[i][j], Nx[i], "Progression", cx[i]) for i in range(4): for j in range(3): if cy[j] == 1.0: geo.mesh.setTransfiniteCurve(V[i][j], Ny[j]) else: geo.mesh.setTransfiniteCurve(V[i][j], Ny[j], "Progression", cy[j]) for i in range(3): for j in range(3): geo.mesh.setTransfiniteSurface(S[i][j]) geo.mesh.setRecombine(2, S[i][j]) geo.synchronize() # ---- z-band extrusion (identical surface set each band -> conformal) ------- base = [(2, S[i][j]) for i in range(3) for j in range(3)] cube_base_idx = base.index((2, S[1][1])) # central square is the cube footprint def graded(n, ratio, fine_at_end): th = [ratio**k for k in range(n)] if fine_at_end: th = th[::-1] tot = sum(th); cum, acc = [], 0.0 for t in th: acc += t/tot; cum.append(acc) cum[-1] = 1.0 return [1]*n, cum def extrude_band(surfs, dz, nE, hs): out = geo.extrude(surfs, 0, 0, dz, numElements=nE, heights=hs, recombine=True) vols, tops = [], [] for k, (d, t) in enumerate(out): if d == 3: vols.append(t); tops.append(out[k-1][1]) return vols, [(2, t) for t in tops] nE, hs = graded(nz_band, z_ratio, fine_at_end=True) v1, top1 = extrude_band(base, (-zc) - (-z_far), nE, hs) # bottom band v2, top2 = extrude_band(top1, 2*zc, [nz_mid], [1.0]) # mid band (cube here) nE, hs = graded(nz_band, z_ratio, fine_at_end=False) v3, top3 = extrude_band(top2, z_far - zc, nE, hs) # top band geo.synchronize() cube_vol = v2[cube_base_idx] fluid_vol = [t for t in (v1 + v2 + v3) if t != cube_vol] gmsh.model.addPhysicalGroup(3, fluid_vol, name="fluid") gmsh.model.addPhysicalGroup(3, [cube_vol], name="cube") # exterior box faces by planar bbox tol = 1e-6 grp = {"inlet": [], "outlet": [], "sides": [], "zMin": [], "zMax": []} for (d, t) in gmsh.model.getEntities(2): x0,y0,zz0,x1,y1,zz1 = gmsh.model.getBoundingBox(2, t) if abs(x1-x0)