Domain: Engineering — Aerospace Engineering
Target concept: At small angles of attack, the flow lines are smooth; when the angle of attack increases to the critical value, the flow separates, generating vortices and turbulence.

Video generation prompt: In the wind tunnel, a two-dimensional airfoil is mounted on a rotating support and placed in a steady airflow. Smoke is released upstream, and the angle of attack of the airfoil is gradually increased.

Evaluation guide:
(i) Target concept: Flow transition from attached laminar flow to separated turbulent flow on a 2D airfoil due to increasing angle of attack.
Minimum mechanism: Steady upstream flow (visualized by smoke), rigid airfoil geometry, fixed-axis rotation enabling monotonic angle change, and observable flow topology response (attachment → separation → vortex shedding).
(ii)Storyline: [Frame 0–3] Smoke emerges steadily from upstream source, flowing straight toward stationary airfoil at low angle: streamlines remain smooth and attached. [Frame 4–6] Airfoil begins rotating upward about its mount; smoke upstream remains unchanged, but streamlines on upper surface progressively bend and lift away. [Frame 7–10] At critical orientation, smoke visibly detaches near upper-surface mid-chord, forming a compact, rotating vortex region downstream; lower-surface flow remains attached. All events occur from fixed frontal/side orthographic viewpoint, with no camera movement or occlusion.

Manual:
Experimental Procedure
1. Mount a 2D airfoil on a rotating support inside a wind tunnel test section.
2. Release steady smoke upstream of the airfoil.
3. Gradually rotate the support to increase the airfoil"s angle of attack.
Observation of Experimental Phenomena
- At low angle: smoke forms smooth, parallel streamlines flowing over both surfaces.
- At critical angle: smoke detaches from upper surface near mid-chord/trailing edge, forming visible vortices and turbulent mixing.
Summary of Experimental Principles
At small angles of attack, the flow lines are smooth; when the angle of attack increases to the critical value, the flow separates, generating vortices and turbulence.

Prompt Grounding rubric:
level_1: No airfoil is visible; no rotating support is present; there is no indication of steady airflow (no smoke or streamlines); no smoke release occurs upstream; no angle-of-attack change is observable; the scene does not resemble a wind tunnel test section.
level_2: At least one of the airfoil, rotating support, or smoke is present, but there is no coordinated sequence of upstream smoke release followed by a gradual angle-of-attack increase; the airfoil and support are not shown mounted together; or the smoke does not originate upstream of the airfoil.
level_3: The airfoil is visibly mounted on a rotating support inside a wind-tunnel-like enclosure, smoke is released upstream of it, and a change in angle of attack is implied by the visible rotation of the support relative to the upstream smoke direction; the airfoil, support, and smoke are all present and spatially coherent.
level_4: All conditions for score 3 hold, AND the smoke flows continuously from its upstream origin toward the airfoil, AND the airfoil rotates smoothly about its mounting axis, AND the smoke's path toward the airfoil shows no visible break or jump, AND there is no visual gap between the smoke source, the flow path, and the airfoil's position.
level_5: All conditions for score 4 hold, AND the smoke originates only from the upstream source (never from the sides or downstream of the airfoil), AND the smoke stays within a single visible horizontal plane consistent with a 2D flow setup, AND the airfoil's leading edge starts aligned with the upstream smoke direction at low angle and then visibly rotates while the smoke source itself stays fixed, showing a controlled, gradual change in angle of attack.

Scientific and Causal Correctness rubric:
level_1: Smoke flows identically over the entire airfoil surface at every angle shown, with no separation, no vortices, and no turbulence even at the highest angle reached; there is no visible difference in flow behavior as the angle changes; the flow lines never distort or detach.
level_2: Smoke disperses chaotically in all directions with no directional alignment; there is no visible relationship between the airfoil's orientation and the smoke's behavior; vortices or turbulence appear at random points unrelated to the angle-of-attack change; the flow never looks smooth or attached at any stage.
level_3: Smoke shows smooth, parallel, unbroken streamlines approaching the airfoil at low angle of attack; at a higher angle, the streamlines visibly detach from the upper surface near mid-chord or the trailing edge and form a localized region of swirling, disordered motion; this detachment happens only after the airfoil's orientation changes and lines up in time with the increased angle.
level_4: All conditions for score 3 hold, AND the flow separation occurs only on the upper surface, never the lower surface, AND the detached region appears downstream of the leading edge or the point of maximum curvature, AND the vortices stay close to the airfoil surface rather than spreading upstream, AND no separation is visible at low angle; it appears strictly after the angle increases.
level_5: All conditions for score 4 hold, AND the onset of separation lines up closely in time with the airfoil's rotation (no noticeable lag or early onset), AND the upstream smoke stays straight and undisturbed before, during, and after separation begins, AND no separation appears on the lower surface at any point, AND the vortex that forms downstream is compact and clearly rotational rather than a general diffuse cloud, consistent with classic 2D airfoil stall.

Spatiotemporal Consistency rubric:
level_1: The airfoil jumps between orientations with no visible rotation; smoke appears or vanishes instantly with no visible origin or fade-out; the rotating support visibly detaches from the airfoil mid-sequence; the lighting or shadows shift abruptly between frames; the airfoil changes size or shape in a single cut.
level_2: The airfoil rotates but the support beneath it stays visually static, as if disconnected; smoke appears to pass straight through the solid airfoil; the smoke's origin point shifts sideways or vertically mid-flow; the airfoil flickers or breaks apart across frames; the background geometry stretches or scales inconsistently.
level_3: The airfoil stays visibly attached to the rotating support throughout; the smoke originates from one stable upstream location and moves continuously toward the airfoil; every object keeps a consistent size, shape, and position relative to the others; no frame shows tearing, warping, or an occlusion that breaks physical sense.
level_4: All conditions for score 3 hold, AND the airfoil's rotation is smooth and moves in one direction only (no reversing, jerking, or stalling mid-motion), AND the smoke flow has no visible gaps, skips, or restarts across frames, AND there is no sudden lighting shift or shadow jump, AND the camera viewpoint stays fixed and perpendicular to the flow plane.
level_5: All conditions for score 4 hold, AND the airfoil's rotation axis stays visually anchored in the same spot with no perceptible drift or wobble over the sequence, AND the smoke's density and brightness stay even along its length, AND no motion blur is heavy enough to obscure the flow structure, AND the foreground airfoil and the background grid or wall markings show no visible relative shift as the camera holds its position.