schema_version: 1 kind: assembly name: mixer-01 intent: >- Sealed magnetic-drive paddle mixer for water from sources/mixer-01-spec.md (authoritative): a D50 x 25 cylindrical polypropylene housing with an axial D12 inlet tube in the lid, a radial D10 outlet tube in the side wall and a fixed D6 pin, a four-blade D40 acetal paddle impeller spinning on the pin, a purchased D30 x 40 motor body under the floor (it drives the impeller through the floor by a magnetic coupling that is not modelled), and the derived water region between the inlet (z = 48) and outlet (x = 58) port planes. At the design point (1500 rpm, 2.0 L/min) predict the static pressure rise and the impeller torque from a steady MRF CFD on a three-level mesh ladder, an Euler-head estimate of the pressure rise, and the water volume; the spec requires a static pressure rise of at least 500 Pa. units: {length: mm, angle: deg} frame: origin: centre of the chamber floor's inside face, on the impeller and pin axis axes: {x: "horizontal, toward the outlet tube", y: completes a right-handed frame, z: "impeller axis, up toward the inlet tube"} datums: - {name: A, description: chamber floor inside face z = 0} - {name: B, description: impeller and pin axis x = y = 0} - {name: C, description: "outlet tube axis y = 0, z = 12.5, along +x"} envelope: {min: [-28.0, -28.0, -43.0], max: [58.0, 28.0, 48.0], tolerance: 0.1} datum_part: housing parts: - name: housing kind: modelled design: mixer-01-housing intent: >- Housing in its own frame, which is the assembly frame: origin at the centre of the chamber floor's inside face, +z up the impeller axis, +x toward the outlet. One solid. Closed cylindrical chamber of inner radius 25.0 (D50) over z 0..25; side wall 3.0 thick (outer radius 28.0) over z -3..28; floor 3.0 thick z -3..0; lid 3.0 thick z 25..28. Inlet tube on the axis: inner diameter 12.0, outer diameter 16.0, z 28..48, open at z = 48; its D12 bore continues through the lid into the chamber (bore z 25..48). Outlet tube on the axis y = 0, z = 12.5 along +x: inner diameter 10.0, outer diameter 14.0, from the side wall's outer face to its open end at x = 58; its D10 bore continues through the side wall into the chamber. Fixed pin on the axis, diameter 6.0, from the floor z = 0 to a flat top at z = 12, part of the same solid. No fillets or chamfers are stated. Interfaces: the pin carries the impeller (its D8 hub bore with 1.0 radial clearance, the hub's bottom face 1.0 above the floor at z = 1); the floor's underside z = -3 is the seat of the D30 motor face, centred on the axis; the open tube ends z = 48 and x = 58 are the fluid port planes. Bounding box x -28..58, y -28..28, z -3..48; volume about 31076 mm3. material: polypropylene density_kg_m3: 900.0 - name: impeller kind: modelled design: mixer-01-impeller intent: >- Four-blade paddle impeller in its own frame: origin at the centre of the hub's bottom face, +z along the rotation axis, one blade along +x. One solid. Hub: outer diameter 12.0, z 0..10, with a through bore of diameter 8.0 on the axis (it rides on the housing's D6 pin with 1.0 radial clearance). Four flat radial blades at 0, 90, 180 and 270 deg about +z, each 2.0 thick tangentially and centred on its radius line (|y| <= 1.0 for the +x blade), from the hub at radius 6.0 (the roots merge into the hub) to tips on radius 20.0, over z 1..9 (8.0 tall). No fillets or chamfers are stated. Interfaces: the D8 bore and the bottom face (1.0 above the housing floor when placed) run on the pin; the whole outer surface is the rotating wetted wall. Bounding box x -20..20, y -20..20, z 0..10; volume about 1525.6 mm3 (hub 628.3, each blade 224.3). material: acetal density_kg_m3: 1410.0 - name: motor kind: purchased catalog: {name: motor, kind: cylinder, point: [0.0, 0.0, -40.0], direction: [0.0, 0.0, 1.0], radius: 15.0, length: 40.0} description: >- Purchased motor body in its own frame: origin at the centre of its top (output) face, +z along its shaft; a plain D30 x 40 cylinder over z -40..0. It turns the impeller through the floor by a magnetic coupling that is not modelled, so the body itself is stationary. - name: water kind: derived role: fluid material: water at 20 degC description: >- The water filling the chamber and both tube bores around the impeller and the pin, bounded by the housing and the impeller and capped at the inlet plane z = 48 and the outlet plane x = 58 (built in the assembly source). parameters: - {name: impellerLift, value: 1.0, unit: mm, provenance: stated, tolerance: 0.01, source: sources/mixer-01-spec.md Placement, description: "hub bottom face above the floor; the impeller origin sits at (0, 0, 1)"} - {name: pinClearance, value: 1.0, unit: mm, provenance: derived, tolerance: 0.01, formula: "(hubBoreDiameter 8.0 - pinDiameter 6.0) / 2", description: radial clearance of the hub bore on the pin} - {name: tipGap, value: 5.0, unit: mm, provenance: derived, tolerance: 0.01, formula: "chamberRadius 25.0 - bladeTipRadius 20.0", description: blade tip to chamber wall} - {name: lidGap, value: 14.0, unit: mm, provenance: derived, tolerance: 0.01, formula: "lid underside 25.0 - hub top (1.0 + 10.0)", description: hub top to the lid} joints: - name: motorMount kind: rigid parent: housing child: motor parent_frame: {origin: [0.0, 0.0, -3.0], axis: [0.0, 0.0, 1.0], ref: [1.0, 0.0, 0.0]} child_frame: {origin: [0.0, 0.0, 0.0], axis: [0.0, 0.0, 1.0], ref: [1.0, 0.0, 0.0]} description: the motor's top face against the floor's underside z = -3, on the axis - name: impellerSpin kind: revolute parent: housing child: impeller parent_frame: {origin: [0.0, 0.0, 1.0], axis: [0.0, 0.0, 1.0], ref: [1.0, 0.0, 0.0]} child_frame: {origin: [0.0, 0.0, 0.0], axis: [0.0, 0.0, 1.0], ref: [1.0, 0.0, 0.0]} angle: 0.0 drive: {kind: motor, case_value: impellerRpm, description: "turned by the motor under the floor through the unmodelled magnetic coupling; positive about +z (counter-clockwise seen from above)"} description: the impeller on the pin, its hub's bottom face 1.0 above the floor; at rest the +x blade points at the outlet - name: waterFixed kind: rigid parent: housing child: water parent_frame: {origin: [0.0, 0.0, 0.0], axis: [0.0, 0.0, 1.0], ref: [1.0, 0.0, 0.0]} child_frame: {origin: [0.0, 0.0, 0.0], axis: [0.0, 0.0, 1.0], ref: [1.0, 0.0, 0.0]} description: the derived water region is built in the assembly frame fluid_volumes: - name: water body: water walls: [housing] minus: [impeller] caps: - {name: inletCap, point: [0.0, 0.0, 48.0], normal: [0.0, 0.0, 1.0]} - {name: outletCap, point: [58.0, 0.0, 12.5], normal: [1.0, 0.0, 0.0]} seed: [12.3, 5.7, 17.1] volume: {expected: 52425.0, tolerance_rel: 0.01, provenance: derived, note: "chamber 49087.4 + inlet bore 2601.2 + outlet bore 2601.7 - pin 339.3 - impeller 1525.6 (brief section 5); the spec states about 5.24e4"} description: seed above the impeller between the axis and the wall, at least 6 mm from every wall boundaries: - {name: inlet, role: inlet, body: water, select: plane, point: [0.0, 0.0, 48.0], normal: [0.0, 0.0, 1.0], area: {expected: 113.097, tolerance_rel: 0.01, provenance: derived, note: "pi x 6.0^2, the D12 inlet bore"}} - {name: outlet, role: outlet, body: water, select: plane, point: [58.0, 0.0, 12.5], normal: [1.0, 0.0, 0.0], area: {expected: 78.540, tolerance_rel: 0.01, provenance: derived, note: "pi x 5.0^2, the D10 outlet bore"}} - {name: impellerWall, role: rotating_wall, body: water, select: touching, touching: impeller, description: the impeller's whole wetted surface (rotating)} - {name: housingWall, role: wall, body: water, select: rest, description: "every other wetted housing surface, stationary: chamber, lid, floor, both bores and the pin (also where they lie inside the rotating zone)"} operating_cases: - {id: design, values: {impellerRpm: 1500.0, flowLMin: 2.0, inletTurbulencePct: 5.0}, units: {impellerRpm: rpm, flowLMin: L/min, inletTurbulencePct: "%"}, split: development, source: sources/mixer-01-spec.md Operating point, description: the design point} observables: - {id: pressureRiseCfd, quantity: pressure_rise, unit: Pa, simulation: cfd, case: design, averaging: steady, min: 500.0, description: "static pressure, outlet plane minus inlet plane, area-averaged; the spec requires at least 500 Pa"} - {id: impellerTorque, quantity: torque, unit: N m, simulation: cfd, case: design, body: impeller, averaging: steady, description: the torque the impeller absorbs about its axis} - {id: pressureRiseEuler, quantity: pressure_rise, unit: Pa, simulation: euler, case: design, averaging: steady, description: "Euler-head estimate of the same static pressure rise, for comparison with the CFD"} - {id: eulerHeadIdeal, quantity: euler_head, unit: m, simulation: euler, case: design, averaging: steady, description: the ideal Euler head (no hydraulic efficiency) behind the estimate} - {id: waterVolume, quantity: fluid_volume, unit: mm3, body: water, description: the volume of the derived water region} simulations: - id: cfd physics: cfd_steady solver: openfoam cases: [design] bodies: [water, impeller] inputs: fluidDensity: {value: 998.2, unit: kg/m3, provenance: stated, source: sources/mixer-01-spec.md Fluid} fluidViscosity: {value: 1.002e-3, unit: Pa s, provenance: stated, source: sources/mixer-01-spec.md Fluid} settings: {flow_key: flowLMin, speed_key: impellerRpm, turbulence_key: inletTurbulencePct, inlet_diameter_mm: 12.0, cell_mm: 1.5, surface_level: 1, iterations: 1500, processes: 4, timeout_s: 1200} refinement: [1.0, 0.75, 0.5625, 0.421875] outputs: [pressureRiseCfd, impellerTorque] description: >- Steady MRF (simpleFoam, k-omega SST) of the water region with the impeller rotating at the case speed; 1.5 mm interior cells with walls one level finer at level 1.0, then three levels each refining everywhere at a constant factor ratio 4/3; the grid-convergence index is taken over the finest three, and the finest level (about 498k cells) is sized to solve within the spec's 20 minutes on 4 cores. - id: euler physics: reduced solver: reduced:pump_euler cases: [design] bodies: [impeller] inputs: fluidDensity: {value: 998.2, unit: kg/m3, provenance: stated, source: sources/mixer-01-spec.md Fluid} bladeCount: {value: 4.0, unit: "", provenance: stated, source: sources/mixer-01-spec.md Dimensions (impeller blades)} bladeOutletAngle: {value: 90.0, unit: deg, provenance: stated, source: sources/mixer-01-spec.md Predictions item 2} bladeOutletWidth: {value: 8.0, unit: mm, provenance: stated, source: sources/mixer-01-spec.md Predictions item 2} hydraulicEfficiency: {value: 0.35, unit: "", provenance: inferred, rationale: "the spec states it is not known; radial blades without a volute or diffuser turn at most the reaction part (one half to two thirds) of the Euler work into static pressure, and open unshrouded paddles with a 5 mm tip gap in a flat chamber lose more of it, so 0.35 with a wide band (0.2..0.5)", uncertainty: 0.15} settings: {flow_key: flowLMin, speed_key: impellerRpm} outputs: [pressureRiseEuler, eulerHeadIdeal] description: Euler-head estimate from the placed impeller's tip radius at the case speed and flow, for comparison with the CFD acceptance: clearances: - {name: impellerOnPin, a: impeller, b: housing, min_gap: 0.9, max_gap: 1.1, description: "at rest the nearest approach is 1.0: the hub bore to the pin (radial) and the hub's bottom face to the floor (tips 5.0 to the wall, 14.0 to the lid)"} - {name: motorSeat, a: motor, b: housing, min_gap: 0.0, max_gap: 0.05, description: the motor's top face seats on the floor's underside z = -3} - {name: impellerClearOfMotor, a: impeller, b: motor, min_gap: 3.5, description: "the floor separates them: hub bottom z = 1 to motor top z = -3"} motions: - {name: impellerTurn, drive: impellerSpin, range: [0.0, 360.0], steps: 36, pairs: [[impeller, housing], [impeller, motor]], description: "a full impeller turn free of interference with the housing (the water region is fluid, not checked)"} references: - {path: sources/mixer-01-spec.md, kind: text, role: authoritative, sha256: 7c08f09900a1078122226978351d2ff7878b3adda1dc49b70bada1a4dcf2a8a1} open_questions: - "The spec states the hydraulic efficiency is not known; the Euler estimate uses an inferred 0.35 with a standard uncertainty of 0.15, so it is a comparison only and the 500 Pa requirement is gated on the CFD prediction alone." - "The spec places the impeller by translation only; its rest phase is taken as a blade along +x pointing at the outlet (angle 0). The frozen-rotor (MRF) CFD depends weakly on this phase." - "The pin, the floor and the lid are stationary walls even where they lie inside the rotating (MRF) zone around the impeller; the zone's extent is the CFD adapter's choice." - "The magnetic coupling and the motor's internals are not modelled; the motor is a stationary D30 x 40 cylinder whose material and mass the spec does not give, so the contract sets no assembly mass or centre of mass." - "No fillets, chamfers, draft or tube-to-wall blends are stated; both parts are drafted with sharp edges. The blade tips are trimmed to radius 20.0 (a flat tip would reach 20.03 at its corners)." - "The mesh ladder (cell 1.5 mm, walls one level finer, factor ratio 4/3) is [1.0, 0.75, 0.5625, 0.421875]; the 1200 s timeout enforces the spec's 20 minutes per level on 4 cores. If the finest three still do not converge (GCI above 0.05), a fifth 4/3 level (about 926k cells, about 1850 s) breaks that budget, so the next lever is the wall treatment or the ladder's shape rather than another level." - "ECR 1, waterVolume: quantity `volume` -> `fluid_volume`. Evidence: for an observable without a simulation the evaluator measures `fluid_volume`, not `volume`, so the prediction came back unavailable and the assembly lint rejected the contract; the domains stage measured the sealed water region at 52,425 mm3 (domains.json fluids.water.volume), the centre of the analytic band." - "ECR 1, cfd ladder: [1.0, 0.75, 0.5625] -> [1.0, 0.75, 0.5625, 0.421875], a finer fourth level at the same 4/3 factor ratio; the 1500 iterations and every setting are unchanged so the three run levels are reused. Evidence: 76,908, 143,786 and 267,558 cells (1.86x per level, cell-count ratio 1.23) in 670, 726 and 533 s on 4 processes; the pressure rise 3739, 3878, 4079 Pa diverges (+139, +201 Pa; GCI 0.288 at Fs 3, u_discretisation 1176 Pa) and the torque oscillates (4.793e-3, 4.650e-3, 4.738e-3 N m; GCI 0.178). At the finest level's 1.99 ms per cell the new level is about 498k cells and 990 s, inside the 1200 s timeout; starting finer at the same ratio needs a 0.3164 level (about 926k cells, 1850 s), over the spec's 20 minutes, and a smaller ratio would push the cell-count ratio further below 1.3. The GCI is now taken over [0.75, 0.5625, 0.421875] and the prediction is the 0.421875 level. The first two levels ran 2.5 to 4.4 times slower per cell beside an 8-process run of another machine, so the new level needs the cores to itself to stay inside the timeout." - "The spec gives no outlet back-pressure or inlet turbulence length scale; the CFD adapter's defaults apply (static-pressure outlet, length scale from the 12.0 inlet diameter)."