docs: VIV predeclare — (30D,30D) centre, conditional .01D seed, 150-cycle budget incl. scoring

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/validation/leontini_viv_predeclare.md

@@ -27,8 +27,10 @@ this page is jointly agreed.
 
 - D = 40, MRT, dense double buffer; U_lat = .04, nu = U D / 150 = .010667,
   tau = .532.
-- Box 75 D × 60 D (3000 × 2400) with the cylinder 30 D from the inlet, 45 D
-  from the outlet, centred in y (Kolahdouz §4.1.1).
+- Box [0, 75 D] × [0, 60 D] (3000 × 2400) with the cylinder centre at
+  (30 D, 30 D): 30 D from the inlet, 45 D from the outlet, centred in y
+  (Kolahdouz §4.1.1). Qin's own box ([0, 40 D] × [0, 20 D], centre (10 D, 10 D))
+  is the target paper's, not ours.
 - Boundaries: uniform Zou–He inlet, NEQ outlet (rho = 1, backflow clamp),
   free-slip y walls. Kolahdouz uses a traction outlet: declared mismatch.
 - Qin's own VIV box (40 D × 20 D) is not used; a smaller box would be a
@@ -55,22 +57,29 @@ this page is jointly agreed.
 
 ## Window, failure semantics, acceptance (engineering, development stage)
 
-- Start: fluid at rest at U = 0 except the uniform inlet (impulsive start as
-  in the reference), body at rest. The reference states no perturbation; a
-  numerically symmetric start can delay or suppress lift, so one declared
-  seed is used: initial structural displacement y0 = +.05 D (2 cells) with
-  v0 = 0, released at t = 0. No other perturbation; not changed afterwards.
+- Start (source-faithful): fluid at rest except the uniform inlet, body at
+  rest at the declared centre, y(0) = v(0) = 0.
+- Seed policy (conditional, declared): exact mirror symmetry can suppress
+  lift. If max |y| over the last 5 T_n before t = 40 T_n (200,000 steps) is
+  below .01 D, apply one labelled seed at that step: body centre displaced by
+  +.01 D in y (v = 0), `seed_applied=true` and its step logged; the run
+  continues under the same cap. Missing shedding is a diagnostic, never an
+  "A = 0 pass"; the seed is not changed or repeated after seeing results.
 - Response cycles: delimited by consecutive upward zero crossings of y about
   its running mean; per-cycle peak = max |y − mean| in that cycle.
 - Settled when the per-cycle peak changes ≤ 2 % between consecutive 10-cycle
-  windows and the last 5 cycle peaks agree within 1 %. The 20 scoring cycles
-  follow settling and are included in the cap of 150 response cycles from
-  t = 0 (about 150 × 5,000 = 750,000 steps, t U/D ≈ 750); total steps and
-  t U/D are reported.
-- Growth transient vs instability: amplitude growth from the seed that stays
-  below 1.0 D (about twice the largest reference peak, .551 D) is a physical
-  transient and is not a failure by itself. Instability = |y| > 1.0 D, a
-  non-finite value, or the offset box being reached.
+  windows and the last 5 cycle peaks agree within 1 %. Budget: 150 response
+  cycles from the start of motion, including the 20 scoring cycles, so
+  settling must complete by response cycle 130; the score uses the first 20
+  cycles after settling. Cap miss → FAIL-CLOSED.
+- Durations reported: total steps, t U/D, N_resp, measured T_resp (mean
+  upward-crossing interval); N_resp / f_n only as a labelled secondary clock,
+  never as the settling unit.
+- Growth transient vs instability: an envelope that rises and then saturates
+  under the settling windows is a physical transient. Instability =
+  |y| > 1.0 D (about twice the largest reference peak, .551 D), a non-finite
+  value, the offset box being reached, or an envelope still growing at the
+  cap.
 - FAIL-CLOSED and reported (no sub-iteration, no RHS or parameter retune):
   unsettled at the cap, instability as defined above (possible weak-coupling
   instability at m* ≈ 2.55), or no_donor > 0.