Domain: Engineering — Instrument and Meter Engineering
Target concept: Rotameter

Video generation prompt: Mount the rotameter vertically on the clean water pipeline, set the pipeline valve to the closed position, then slowly open the valve to increase the flow rate, and focus the lens on the body of the flow meter and the rotor.

Evaluation guide:
(i) Target concept: Volumetric flow measurement via variable-area principle in a vertically installed rotameter.
Minimum mechanism: Gravity must act parallel to tube axis; fluid must be single-phase liquid (water); float must be denser than fluid and geometrically constrained to move axially only; flow must induce upward drag sufficient to lift float against net downward force.
(ii)Storyline: Frame 0–2: Static shot showing vertically mounted rotameter on clear pipeline, valve fully closed, rotor at bottom rest position. Frame 3–7: Continuous valve handle rotation from closed → partially open, synchronized with smooth, monotonic upward displacement of rotor inside tapered tube. Frame 8–10: Valve stabilizes in open position; rotor holds new elevated position; no oscillation, slip, or settling. Perspective: Fixed frontal view centered on rotameter body and internal rotor; no occlusion; full tube length and rotor fully visible throughout.

Manual:
Experimental Procedure
1. Mount rotameter vertically on clean water pipeline.
2. Set pipeline valve to closed position.
3. Slowly open valve to increase flow rate.
Observation of Experimental Phenomena
- Rotameter tube is transparent; rotor is a conical float inside.
- Rotor remains stationary when valve is closed.
- Rotor rises continuously and smoothly as valve opens.
Summary of Experimental Principles
Rotameter measures flow rate by balancing drag force (from fluid) and gravity/buoyancy on a freely suspended float in a tapered tube — vertical orientation is mandatory for correct operation.

Prompt Grounding rubric:
level_1: No rotameter appears in the shot; no water pipeline is shown; no valve is visible anywhere; the clip never shows any of the three key actions: mounting the rotameter vertically, closing the valve, or slowly opening it.
level_2: A rotameter appears but is mounted at an angle rather than upright; the pipeline is visible but the liquid inside looks murky or colored, or the pipe itself isn't shown; a valve is present but you can't tell whether it starts closed or open; the shot never keeps both the rotameter's body and its internal float in view at the same time.
level_3: The rotameter is mounted upright on a visible pipeline; the liquid in the pipe looks clear, consistent with clean water; the valve starts in a closed position before any flow begins; the shot keeps the rotameter's body and the float inside it in frame; the sequence shows mounting, closing, then slow opening in that order.
level_4: Everything required for score 3 holds, and additionally the valve-opening motion plays out as one continuous action with no jump cuts or frozen frames; the rotameter stays fully inside the frame the whole time; the float reads clearly as a separate moving piece inside the tapered tube.
level_5: Everything required for score 4 holds, and additionally the float doesn't start moving until the valve actually begins to open; the float's position keeps rising steadily as the valve opens further; nothing else in the shot blocks the rotameter body or float at any point; the camera holds the same fixed, centered framing on the rotameter and float with no panning, tilting, or zooming.

Scientific and Causal Correctness rubric:
level_1: The float sits still even though the valve is open; the float moves downward or sideways as the valve opens instead of rising; the rotameter is shown lying on its side or upside down; the liquid in the tube looks like gas or is too opaque to see through; opening the valve produces no visible effect on the float at all.
level_2: The float moves, but not in step with the valve: it starts before the valve opens, or stops moving while the valve is still being turned; the rotameter tilts noticeably off vertical (more than roughly 10° from upright); the liquid in the tube looks tinted, cloudy, or is missing; the float doesn't look like the expected cone-shaped weight.
level_3: The float is cone-shaped and only rises while the valve is actively being opened; the rotameter stands vertical; the liquid in the tube is clear and fills it without gaps or bubbles breaking up the column; the float starts moving once the valve begins opening and settles once the valve stops turning, so the cause-and-effect between valve and float is easy to follow.
level_4: Everything required for score 3 holds, and additionally the float's rise is smooth and one-directional with no bouncing, stalling, or reversing partway; the liquid fills the tapered section evenly with no overflow or dry patches; the float stays centered in the tube and fully submerged the whole time it's moving.
level_5: Everything required for score 4 holds, and additionally a higher float position clearly corresponds to a further-open valve, with no lag between turning the valve and the float responding; no dripping, splashing, or leaking appears at any joint; no air bubbles or swirling appear in the tube; the float's surface catches the light the way a solid object would, not like something transparent or glowing.

Spatiotemporal Consistency rubric:
level_1: The rotameter or valve suddenly appears in a different spot between moments; the scene's lighting flashes, cuts to black, or shifts color with nothing to explain it; the rotameter looks cracked or bent in a way solid metal or glass wouldn't; the pipeline looks disconnected from the rotameter; the float vanishes and reappears without anything blocking the view.
level_2: The rotameter's position shifts noticeably sideways between moments; the valve handle appears to snap to a new angle rather than turning smoothly; the float seems to freeze then jump ahead; the direction the light is coming from seems to reverse without warning.
level_3: The rotameter stays in the same place relative to the pipeline throughout; the valve stays attached and aligned with the pipe; the float stays inside the tube; the lighting and the direction shadows fall stay the same for the whole clip; nothing jumps, freezes, or warps at any point.
level_4: Everything required for score 3 holds, and additionally the camera holds its framing steady with no visible drift or breathing; the edges of the pipeline and rotameter stay crisp rather than blurring in a way that hides their shape; the float's rise looks like a straight vertical path up the tube rather than wandering side to side.
level_5: Everything required for score 4 holds, and additionally none of the object outlines look torn or flickering between moments; the relative depth of the pipeline, valve, and rotameter stays consistent with no odd shifting of one relative to another; no frames are skipped or repeated; the tube and float keep their true round and conical shapes without warping into an oval or bent look.