research: reuse quadrature and clarify snapshot and VIV coordinates

research/duetsch_re100_kc5/protocol.py

@@ -8,6 +8,7 @@ s/T in [0.25 + (k-1), 0.25 + k); cycle 0 is the startup quarter.
 from __future__ import annotations
 
 import math
+from functools import lru_cache
 
 import numpy as np
 
@@ -53,10 +54,16 @@ def bin_phase(s, T):
     return None
 
 
+@lru_cache(maxsize=8)
+def _quadrature_rule(points):
+    """Reuse the nodes and weights, which depend only on quadrature order."""
+    return np.polynomial.legendre.leggauss(points)
+
+
 def interval_bases(n, T, points=16):
     """Single-step interval averages over [n, n + 1] of cos phi |cos phi| and sin phi
     (phi in radians = 2 pi s / T - pi / 2), Gauss-Legendre quadrature."""
-    x, w = np.polynomial.legendre.leggauss(points)
+    x, w = _quadrature_rule(points)
     s = int(n) % T + 0.5 * (x + 1.0)  # periodic: identical bases in every cycle
     phi = 2.0 * np.pi * s / T - 0.5 * np.pi
     c = np.cos(phi)

research/viv_re150/run.py

@@ -1,8 +1,9 @@
 """One-shot predeclared VIV run (docs/validation/viv_re150_predeclare.md).
 
-Re 150, U* = 5, m/(rho D^2) = 2, zeta = 0, D = 40 on a 75 D x 60 D native
-channel (uniform inlet, NEQ outlet, free-slip y walls), cylinder at
-(30 D, 30 D). Structural RHS = CME + Wen (diagnostics: raw CME, node terms).
+Re 150, U* = 5, m/(rho D^2) = 2, zeta = 0, D = 40 on a nominal 75 D x 60 D
+lattice (uniform inlet, NEQ outlet, free-slip y walls). The cylinder is at
+(30 D, (ny - 1)/2); y-wall planes are .5 and ny - 1.5 in lattice coordinates.
+Structural RHS = CME + Wen (diagnostics: raw CME, node terms).
 Research driver only: Simulation API, no production change.
 
     PYTHONPATH=src python research/viv_re150/run.py --out /path/outside/checkout