Domain: Engineering — Aerospace Engineering
Target concept: Smoke lines around an airfoil in a wind tunnel

Video generation prompt: In the wind tunnel, a thin airfoil is horizontally installed, and smoke lines are continuously injected upstream under steady airflow conditions, while the airfoil is gradually rotated to increase the angle of attack.

Evaluation guide:
(i) Target concept: Steady-state visualization of streamlines via smoke wires in a wind tunnel, demonstrating how angle-of-attack variation alters streamline geometry around a lifting body.
Minimum mechanism: Continuous smoke injection + steady laminar airflow + rigid-body airfoil rotation about fixed axis + optical transparency of tunnel walls + absence of unsteady disturbances (e.g., gusts, vibrations, vortex shedding).
(ii)Storyline: [Frame 0–2] Airfoil horizontal; smoke lines straight, parallel, uniformly spaced upstream; no distortion near airfoil. [Frame 3–5] Rotation begins; smoke lines near leading edge start converging and curving smoothly around both surfaces; stagnation point appears. [Frame 6–8] Rotation continues; upper-surface lines arch more sharply; lower-surface lines compress; stagnation point migrates downward; asymmetry intensifies. [Frame 9–10] Final orientation reached; all smoke lines remain attached, continuous, and geometrically consistent with airfoil contour: no separation, no detachment, no turbulence. Perspective: Fixed frontal/slightly oblique view showing full airfoil, upstream injection zone, and adjacent tunnel walls; no occlusion; lighting uniform and front-dominant to ensure visibility of smoke contrast.

Manual:
Experimental Procedure
1. Mount thin, symmetrical airfoil horizontally inside transparent-walled wind tunnel test section.
2. Initiate steady, laminar airflow; confirm uniform background flow.
3. Begin continuous smoke injection upstream of airfoil.
4. While smoke flows steadily, gradually rotate airfoil about its quarter-chord axis to increase angle of attack.
Observation of Experimental Phenomena
- Smoke lines remain straight and parallel upstream of airfoil.
- Near airfoil, smoke lines bend smoothly around upper and lower surfaces.
- As angle of attack increases, bending becomes increasingly asymmetric: stronger curvature above, compression below.
- A visible stagnation point forms near leading edge and shifts downward with rotation.
Summary of Experimental Principles
Smoke lines visualize instantaneous streamlines in steady, incompressible flow. Their curvature reveals local pressure gradients; asymmetric bending indicates lift generation. Increasing angle of attack amplifies circulation and adverse pressure gradient on upper surface, altering streamline topology per inviscid and boundary-layer theory.

Prompt Grounding rubric:
level_1: No airfoil present; no smoke injection visible; no rotation motion observed; no steady airflow indication (e.g., uniform background flow cues); scene does not depict a wind tunnel environment.
level_2: Airfoil is present and horizontally oriented at start, but smoke lines are absent or static/non-flowing; rotation action is missing or replaced by translation/translation-only motion; wind tunnel enclosure (transparent walls, test section boundaries) is partially or fully missing.
level_3: Airfoil is present, initially horizontal; smoke lines are continuously injected upstream and visibly stream downstream; airflow appears steady (no turbulence bursts, pulsation, or chaotic eddies in undisturbed region); airfoil begins rotation (orientation visibly changes from horizontal toward higher angle), and this rotation occurs *while* smoke lines remain active and flowing.
level_4: All elements of 3-score are present, AND the airfoil remains fixed in position (no lateral/vertical translation during rotation); smoke injection point is upstream of airfoil (not at leading edge or on surface); smoke lines maintain continuity and coherence upstream of airfoil throughout rotation; viewpoint is fixed, showing full airfoil and adjacent flow field without cropping or occlusion.
level_5: All elements of 4-score are present, AND smoke lines exhibit clear spatial differentiation before/after airfoil: straight and parallel upstream, then bending/distorting in proximity to airfoil surface as angle of attack increases; rotation is smooth and monotonic (no reversal, hesitation, or jerking); no visual artifacts (e.g., clipping, alpha glitches, floating objects, inconsistent lighting) disrupt the depiction of the wind tunnel test section.

Scientific and Causal Correctness rubric:
level_1: Smoke lines do not respond to airfoil orientation; smoke flows identically before and after rotation; airfoil rotates but shows no aerodynamic influence on flow (e.g., no deflection, no stagnation line formation, no separation onset); flow remains perfectly straight and uniform across entire frame regardless of airfoil angle.
level_2: Smoke lines exist but show no causal relationship to airfoil: either they pass through the airfoil as if transparent, or they deflect randomly/unpredictably; rotation produces no systematic change in smoke pattern; no discernible stagnation point or streamline curvature near leading edge even at higher angles.
level_3: Smoke lines are visibly bent around the airfoil surface as rotation progresses; upstream lines remain straight and parallel; near the leading edge, lines converge and curve smoothly around the upper/lower surfaces; no flow reversal or separation bubble is required at this level, but curvature must be continuous and symmetric for low angles.
level_4: All elements of 3-score are present, AND as rotation continues, smoke lines increasingly diverge above and below the airfoil; upper-surface lines accelerate and arch upward, lower-surface lines decelerate and compress; a distinct stagnation point forms near the leading edge and migrates slightly downward as angle increases; no unphysical phenomena (e.g., smoke vanishing, splitting into discrete particles mid-stream, abrupt kinks unrelated to geometry).
level_5: All elements of 4-score are present, AND smoke lines demonstrate progressive distortion correlating with angle increase: at low angles, slight symmetric curvature; at moderate angles, asymmetric bending (stronger upper-surface deflection, lower-surface compression); no smoke line intersects or penetrates the airfoil surface; all lines remain continuous, unbroken, and attached (no detached vortices or turbulent shedding depicted, as those require unsteady conditions contrary to prompt).

Spatiotemporal Consistency rubric:
level_1: Airfoil teleports between positions; smoke lines appear/disappear frame-to-frame without transition; lighting shifts abruptly (e.g., bright → dark without gradient); airfoil texture or color changes discontinuously; background structure (wind tunnel walls) flickers or fractures.
level_2: Airfoil rotates but its aspect ratio or silhouette distorts (e.g., stretching, skewing, perspective collapse); smoke lines jitter violently or stutter (≥2 frames of identical static position followed by jump); camera viewpoint drifts (pan/tilt/zoom) without justification; wind tunnel walls vanish/reappear mid-sequence.
level_3: Airfoil maintains consistent shape, size, and texture throughout; smoke lines flow continuously with no frame drops or teleportation; lighting remains stable (no strobing, pulsing, or shadow jumping); wind tunnel enclosure (e.g., transparent side walls, floor, ceiling) remains fully visible and geometrically consistent; no object flickering or interpenetration.
level_4: All elements of 3-score are present, AND rotation motion is smooth and kinematically plausible (no instantaneous velocity changes); smoke line motion matches airfoil motion timing: no lag or lead between rotation onset and observable flow response; spatial relationships preserved: airfoil stays centered relative to smoke injection point and tunnel walls; no parallax violation (e.g., wall edges misalign across frames).
level_5: All elements of 4-score are present, AND inter-frame motion is fluid with no micro-stutters (no repeated frames, no skipped motion phases); smoke line trajectories follow consistent parabolic/curvilinear paths without kinks or reboots; airfoil’s rotational axis remains fixed in space (no wobble, tilt, or pivot shift); background geometry exhibits zero perspective warping or lens distortion artifacts.