Domain: Engineering — Aerospace Engineering
Target concept: Wind tunnel smoke visualization forms parallel flow lines

Video generation prompt: When the fan reaches a stable rotational speed in the test section of the closed wind tunnel, multiple fine white smoke streams are injected uniformly from the upstream nozzles.

Evaluation guide:
(i) Target concept: Visualization of steady laminar flow via passive tracer (smoke) revealing streamlines as parallel, straight, equidistant trajectories.
Minimum mechanism: Fan must generate fully developed, uniform axial flow in test section; smoke must be neutrally buoyant, low-inertia, and injected at flow velocity-matched conditions to avoid perturbation; no external disturbances (vibrations, drafts, thermal gradients) may disrupt streamline coherence.
(ii)Storyline: [Frame 0–2] Fan already rotating steadily in visible test section → [Frame 3–4] Upstream nozzles activate and emit fine white smoke streams simultaneously → [Frame 5–10] Smoke streams propagate downstream maintaining strict parallelism, constant spacing, and uninterrupted continuity across full field of view; viewpoint remains fixed frontal/side orthogonal to flow axis with unobstructed view of entire test section length.

Manual:
Experimental Procedure
1. Activate fan in closed wind tunnel test section until rotation stabilizes.
2. Inject multiple fine white smoke streams uniformly from upstream nozzles.
Observation of Experimental Phenomena
Downstream, all smoke streams form straight, evenly spaced, non-intersecting parallel lines extending continuously through the test section.
Summary of Experimental Principles
Under steady-state laminar flow in a closed wind tunnel, injected smoke particles follow streamlines; parallel smoke lines visually confirm uniform, non-turbulent velocity profile and absence of flow separation or secondary motion.

Prompt Grounding rubric:
level_1: No closed wind tunnel test section is visible; no fan is present; no upstream injection nozzles are visible; no white smoke appears at any point in the clip.
level_2: The wind tunnel test section is only partially visible (e.g., a single wall or an ambiguous enclosure) and the fan is missing or unrecognizable; no upstream nozzle array is shown; white smoke appears but its origin is unclear or it emerges from a location other than the nozzles.
level_3: The closed test section is fully enclosed and visible, a fan is present and visibly rotating inside it, an array of upstream nozzles is visible at the inlet, and multiple fine white smoke streams are visible originating from those nozzles.
level_4: All conditions for score 3 hold, AND every visible smoke stream originates only from the nozzle array (none appears from the tunnel walls, fan hub, or other extraneous source), AND the fan's rotation is continuous without stopping or restarting, AND smoke injection begins only after the fan is already shown rotating at stable speed, matching the posted sequence.
level_5: All conditions for score 4 hold, AND each nozzle emits a smoke stream of consistent thickness from injection to the far edge of the viewing window, AND the nozzle array, fan, and test-section walls stay fully in frame and correctly positioned for the entire clip with no camera cut, zoom, or reframing, AND no nozzle, fan blade, or tunnel wall changes shape, duplicates, or disappears at any point.

Scientific and Causal Correctness rubric:
level_1: Smoke shows chaotic swirling, rapid dispersion, or upward rising with no parallel alignment at any time; or the fan's rotation direction or speed is inconsistent with sustaining steady laminar flow (e.g., visibly reversing or stalling).
level_2: Smoke streams show strong curvature, merge, split, or cut in and out intermittently; the fan is present but stationary or turning too slowly to sustain flow; smoke does not originate from the nozzles or originates from a non-upstream location.
level_3: Smoke streams are continuous, fine, and white, originate from the upstream nozzles, and extend downstream; the fan is rotating inside the test section; at least three visible streams run parallel to one another for at least half of their visible length.
level_4: All conditions for score 3 hold, AND no stream shows separation, coalescing, or local thickening, AND no vortices, eddies, or side-to-side oscillation appear in any stream, AND the fan's rotation stays visually steady (no visible speeding up or slowing down while smoke is present), AND smoke stays within the test-section walls without distortion from wall impact.
level_5: All conditions for score 4 hold, AND every visible stream keeps the same orientation and the same spacing from its neighbors across the full length of the test section, AND no stream visibly curves, converges, or diverges from a straight path at any point, AND smoke opacity and continuity show no visible flicker or pulsing.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the fan appears or disappears mid-sequence, smoke streams materialize with no visible nozzle origin, the scene's lighting jumps abruptly between distinctly different shadow directions, the tunnel wall visibly fractures or warps, or the video freezes/jumps for more than two consecutive frames.
level_2: Moderate inconsistency: the fan's rotation speed visibly jerks or stutters, smoke streams blink on and off or change thickness abruptly, the lighting shifts noticeably more than twice, part of the apparatus is persistently hidden from view for an extended stretch, or the camera view shifts sideways or rotates instead of staying fixed.
level_3: Minor spatiotemporal flaws only: one brief, isolated flicker in smoke opacity, one soft shift in shadow edge softness, a slight visible wobble in fan rotation that does not change its overall speed or direction, and a fixed camera viewpoint maintained throughout with no object disappearing or the tunnel structure deforming.
level_4: All conditions for score 3 hold, AND no lighting change is detectable across the clip (ambient brightness and shadow direction stay constant), AND fan rotation and smoke motion show no visible jerkiness, AND the fan, nozzles, and smoke streams stay visible without being blocked at any point, AND the tunnel walls show no fisheye stretch or keystone-style skew, AND no frame shows visible tearing or ghosting of moving parts.
level_5: All conditions for score 4 hold, AND no visible misalignment or shift of the fan or nozzle outlines appears between consecutive frames, AND the fan blades and smoke streams show no visible jitter in position from frame to frame, AND brightness and color tone stay visibly constant across the whole clip, AND the nozzles (foreground) and tunnel walls (background) show no visible relative shift as the camera holds its fixed position, AND the smoke streams show no visible warping away from straight, evenly spaced lines.