Domain: Engineering — Aerospace Engineering
Target concept: A straight wing exhibits significant flow separation, while a swept wing features smoother flow lines, illustrating how wing sweep delays boundary-layer separation by relieving the spanwise pressure gradient at low speed.

Video generation prompt: Place the straight-wing and swept-wing models side by side in the wind tunnel test section, inject smoke flow under stable airflow conditions, and observe the differences in flow lines.

Evaluation guide:
(i) Target concept: Visual demonstration of differential boundary-layer separation behavior under steady, low-speed (subsonic) wind-tunnel airflow, where wing planform (straight vs. swept) governs how much spanwise pressure-gradient relief the boundary layer gets before separating. This is a boundary-layer/spanwise-flow phenomenon, not a demonstration of supersonic-flow or wave-drag advantages: those effects only occur at transonic/supersonic speeds and cannot be shown by smoke visualization in a low-speed tunnel.
Minimum mechanism: Stable uniform freestream; smoke as passive tracer faithfully following streamlines; wing models rigid and geometrically accurate (straight = 0° sweep, swept = ≥30° sweep); no external flow disturbance (e.g., supports, fingers) interfering with smoke trajectory.
(ii)Storyline: Frame 1–2: Static wide shot showing both wing models fixed side-by-side inside transparent wind tunnel test section walls. Frame 3–4: Smoke emerges from upstream injection point and enters test section uniformly. Frame 5–8: Smoke encounters both wings simultaneously; immediate separation signature appears on straight wing (chaotic eddies, upstream curl) while swept wing sustains laminar attachment (streamlines bend smoothly with sweep angle). Frame 9–10: Final stabilized view confirms persistent, simultaneous contrast; no temporal lag, occlusion, or drift. Perspective: Fixed frontal or slightly elevated orthographic viewpoint ensuring full visibility of both wings and their full flow fields without parallax distortion.

Manual:
Experimental Procedure
1. Place straight-wing and swept-wing models side-by-side in wind tunnel test section.
2. Stabilize airflow, then inject continuous smoke stream upstream of both models.
3. Observe flow line behavior over each wing surface simultaneously.
Observation of Experimental Phenomena
Straight wing shows discontinuous, recirculating, and reversed smoke streamlines (flow separation); swept wing shows continuous, attached, and smoothly aligned smoke streamlines (delayed separation).
Summary of Experimental Principles
At this tunnel's steady, subsonic test speed, the straight wing's boundary layer only has chordwise pressure relief, so it separates quickly downstream of mid-chord and produces the chaotic smoke pattern. The swept wing lets part of the flow travel spanwise (outboard) along the leading edge, which relieves the adverse pressure gradient the boundary layer feels and delays separation, producing the smooth attached smoke pattern. This is a boundary-layer/spanwise-flow effect, not a demonstration of supersonic aerodynamics: the wave-drag and compressibility benefits of wing sweep only occur at transonic/supersonic speeds and cannot be shown by smoke visualization in a low-speed tunnel.

Prompt Grounding rubric:
level_1: Nothing of the required setup appears: no wind-tunnel test section, no straight-wing or swept-wing model, and no smoke is being injected; the shot does not show a wind-tunnel demonstration at all.
level_2: Only part of the setup is present: e.g., only one of the two wing models (straight or swept) appears, or smoke is visible with no wing model in view, or both models exist but are shown in separate shots or separate test sections rather than together, or smoke is injected without any wing model visible at the same time.
level_3: Both the straight-wing and swept-wing models are visible together, mounted side by side inside a single transparent wind-tunnel test section, and a continuous stream of smoke is injected upstream and flows past both models at the same time.
level_4: Everything in level 3 holds, and additionally the smoke visibly originates from one identifiable upstream source (a wire or nozzle at the front of the test section), both wing models stay rigid and motionless with no visible bending or detachment, and the camera holds a single fixed framing of the test section for the whole clip.
level_5: Everything in level 4 holds, and additionally the smoke stays visibly continuous over both wing surfaces with no gaps or breaks, neither wing model ever blocks the view of the other model's flow field, and the two wings plus their flow fields are framed in a balanced, centered composition so both are equally easy to compare by eye.

Scientific and Causal Correctness rubric:
level_1: The smoke pattern shows no visible difference between the two wings, or the phenomenon is reversed (the swept wing shows the chaotic separated smoke while the straight wing shows the smooth attached streamlines), or the straight wing shows no separation at all despite being unswept.
level_2: A difference exists but is misassigned or ambiguous: separation appears on the swept wing only while the straight wing looks smooth, or the separated smoke only puffs/pulses without forming distinct detached streamlines, or the smoke dissipates before either wing's trailing edge so no comparison is possible.
level_3: The straight wing's smoke visibly breaks up into chaotic, recirculating, or reversed streamlines starting near mid-chord (flow separation), while the swept wing's smoke stays as smooth, forward-flowing streamlines with no visible detachment near its leading or mid-chord region.
level_4: Everything in level 3 holds, and additionally the straight wing's separated, chaotic smoke stays confined to that wing's upper surface without spilling onto its lower surface, and the swept wing's attached streamlines visibly bend to follow its leading-edge sweep angle rather than running straight back parallel to the tunnel walls.
level_5: Everything in level 4 holds, and additionally the contrast is unmistakable at a glance: the straight wing's separated smoke looks dense and sluggish and swirls upward/backward, while the swept wing's attached smoke looks thin and fast and stretches smoothly along the sweep direction, with both contrasting patterns visible together in the same frame at the same time.

Spatiotemporal Consistency rubric:
level_1: One of the wing models suddenly appears in a different position or a different shape from one frame to the next, the smoke stream cuts out and restarts without ever flowing continuously from the injector, the whole clip's brightness suddenly jumps to a different level or the framing cuts to a new shot partway through, a wing model visibly bends and then snaps back to its undeformed shape, or the test-section walls themselves flicker or vanish partway through the clip.
level_2: A smaller but still visible inconsistency: the straight-wing and swept-wing models drift slightly relative to each other between frames, the smoke flow starts and stops in visible jerks rather than flowing continuously, the test-section brightness flickers noticeably, or part of one wing is blocked from view and then unblocked for no physical reason.
level_3: The straight-wing and swept-wing models stay in the same fixed positions relative to each other and to the test-section walls for the whole clip, the smoke streams continuously from the injector through the test section without gaps, the test-section brightness stays constant, and there are no visible cuts or jumps in the footage; the sequence reads as one continuous, physically plausible shot.
level_4: Everything in level 3 holds, and additionally the smoke's thickness and opacity change only in ways explainable by the aerodynamics (e.g., thinning as it disperses downstream, or churning into recirculating eddies behind the straight wing) rather than randomly, both wing models cast a shadow that stays on the same side and at the same strength throughout, and the camera framing does not drift or shift during the sequence.
level_5: Everything in level 4 holds, and additionally the smoke's motion looks like real, physically continuous fluid flow with no rendering artifacts (no frame freezing, no the-footage-plays-backward look, and no smoke teleporting between frames), so that the straight wing's chaotic, recirculating eddies read as a genuine aerodynamic feature rather than a glitch; neither wing model shows any visible shaking, bending, or flutter, and the test-section walls and any background grid lines stay geometrically straight and undistorted in every frame.