Domain: Natural Science — Atmospheric Science
Target concept: A transparent chamber equipped with a fan that gently blows downward, and smoke indicating air sinking and flowing outward.

Video generation prompt: A transparent box with a fan blowing downward at the center top; a lit cigarette is placed near the center and releases smoke, which flows within the box.

Evaluation guide:
(i) Target concept: Forced convective downdraft and boundary-layer divergence in a confined neutral atmosphere.
Minimum mechanism: A sustained downward airflow must impinge on a solid horizontal surface, converting vertical momentum into horizontal advection via conservation of mass and no-slip condition, requiring smoke to serve as passive tracer of bulk air motion.
(ii)Storyline: Frame 1–2: Fan active at center top, cigarette lit near chamber center. Frame 3–4: Smoke emerges and begins vertical descent aligned with fan axis. Frame 5–6: Smoke column maintains coherence while accelerating downward. Frame 7: Smoke contacts bottom surface, with visible flattening and lateral expansion initiation. Frame 8–10: Smoke forms continuous, symmetric outward flow along base, filling lower periphery without upward recirculation. Perspective: Fixed frontal view showing full chamber height and width; no obstructions; smoke must remain visible throughout, with no occlusion by fan, walls, or hands.

Manual:
Experimental Procedure
1. Place a transparent rectangular chamber on stable surface.
2. Mount a small fan at the exact center of the chamber"s top inner surface, oriented to blow straight downward.
3. Ignite a cigarette and hold it near the geometric center of the chamber interior; release smoke steadily for ~2 seconds.
Observation of Experimental Phenomena
Smoke descends vertically in a narrow column due to fan-induced downdraft, contacts the bottom surface, then spreads radially outward in all horizontal directions along the base.
Summary of Experimental Principles
Downward fan airflow creates a localized high-pressure zone that forces ambient air (and smoke) downward; upon hitting the solid base, horizontal pressure gradients drive the air outward — demonstrating forced convection and boundary-layer flow in atmospheric science.

Prompt Grounding rubric:
level_1: No transparent box (chamber) is visible; no fan is present; nothing resembling smoke or a smoke source appears; the scene does not show anything matching the fan-and-chamber setup described in the posted_prompt.
level_2: At least one of the chamber, fan, or smoke source is visible, but the setup is wrong in an important way: the fan faces sideways or upward rather than down, the smoke is released from a corner or edge rather than near the center, the box is opaque or barely visible, or the fan is not mounted at the top-center of the chamber.
level_3: The transparent chamber is fully visible; a fan sits at the top-center of the chamber; smoke is released from near the center of the chamber's interior. All three objects appear as described, but their spatial relationship looks off: for example, the fan is at the top but not clearly centered, or the smoke source is noticeably off-center rather than near the middle of the chamber.
level_4: The chamber is fully visible and clearly transparent; the fan is mounted at the top-center of the chamber with its housing visibly angled to face downward; smoke is released from near the geometric center of the chamber's interior, all matching the posted_prompt's setup, but for a moment something (a hand, a reflection, a camera-angle change) partly blocks a clear view of the fan, the chamber, or the smoke source.
level_5: The chamber is fully visible and unobstructed for the entire clip; the fan is mounted precisely at the top-center of the chamber with its housing clearly angled to face downward; smoke is released from very near the geometric center of the chamber's interior; nothing blocks the view of the chamber, fan, or smoke source at any point, and every object's type, location, and orientation matches the posted_prompt exactly.

Scientific and Causal Correctness rubric:
level_1: The smoke keeps drifting upward or spreads evenly in all directions from the release point regardless of the fan, or it vanishes the instant it's released; the fan's downward airflow has no visible effect on where the smoke goes at all.
level_2: The smoke dips down briefly right after release but then drifts back upward or scatters sideways instead of continuing to the floor; there's no sign of it spreading outward along the chamber's base; the direction the fan blows and the direction the smoke moves don't seem to match up.
level_3: The smoke sinks in a fairly straight column from the release point down to the chamber's floor under the fan's downdraft, then spreads outward once it hits the bottom, but the outward spread only reaches part of the way around (e.g., only to one side) or stops partway rather than covering the base, so the fan-down / smoke-sinks / hits-floor / spreads-out sequence is only partly visible.
level_4: The smoke sinks in a fairly straight column to the chamber floor and then spreads outward continuously in at least three different horizontal directions (say, left, right, and toward the camera), forming a widening ring near the base, with only a small blemish, such as the spread being a little faster on one side than another, or a brief wobble in the descending column that doesn't stop it from reaching the floor and spreading.
level_5: The smoke descends in a straight, unbroken column from the release point to the chamber floor, then spreads outward evenly in every horizontal direction at once, forming a full ring that keeps widening near the base; the smoke never drifts back upward, never pools in one spot, and the entire fan-down / smoke-descends / hits-floor / spreads-outward sequence is visible from beginning to end without any part of it skipped.

Spatiotemporal Consistency rubric:
level_1: The chamber's shape suddenly warps or changes; the fan jumps to a different spot between shots; the smoke appears or disappears instantly with no motion connecting the two states; an abrupt, unexplained shift in lighting or shadow occurs with no motion to cause it; or a wall of the chamber vanishes partway through the clip.
level_2: Several moderate problems appear together: the fan's blades spin inconsistently or jerk in place; the smoke appears to jump more than one chamber-width between frames with no visible path connecting the positions; the chamber flickers between looking transparent and looking solid; or the smoke's motion freezes and skips ahead noticeably more than once.
level_3: One small continuity slip happens: the fan blinks out of view for a moment and then reappears, the smoke's flow pauses briefly and then resumes without any burst of extra speed to catch up, or the chamber's edge looks slightly distorted for an instant, but the fan, chamber, and smoke source all keep their overall shape and position, and the rest of the clip holds together.
level_4: The chamber walls stay rigid and in place; the fan stays centered at the top; the smoke's release point stays fixed near the center; the smoke's motion is continuous with no jumps, freezes, or warping, apart from one small flaw, such as the smoke's edge looking slightly soft or its opacity flickering briefly at one point without disrupting the overall flow.
level_5: The chamber, the fan's position, and the smoke's release point all stay visibly fixed and unchanged for the whole clip; the smoke's descent and its outward spread along the floor move smoothly and continuously with no stutters, repeated frames, or ghost trails; nothing in the scene suddenly deforms, flickers, or breaks apart, and the fan keeps spinning at a steady, believable rate throughout.