schema_version: 1 name: nasa-atb-axisymmetric-bump intent: >- Reconstruct the Bachalo-Johnson axisymmetric transonic bump as ONE solid of revolution for a CFD outer-mould line. The attached spec is inch-native (cylinder diameter 6 in, bump chord 8 in, bump height 3/4 in); convert to millimetres. Frame: +x along the cylinder axis with the bump chord occupying x = 0 to x = c, origin on the axis. Revolve the meridian a full 360 degrees. The bump is a circular arc of radius R1 = 0.5 (t^2 + 0.25 c^2) / t; blend it to the upstream cylinder with a leading-edge fillet R2. The references list R2 as 18.30 cm (use 183.0 mm) with 20.32 cm as a documented alternate (open question, inferred). No trailing-edge fillet. Axial extent is the x-range of the attached surface-point file (nondimensional by the 8 in chord; multiply by 8 inches to get millimetres). Name the two planar end caps. Expose cylinderDiameter, bumpChord, bumpHeight and filletRadius. One solid; export STEP and STL. units: length: mm angle: deg material: null density_kg_m3: null process: CFD outer-mould-line reconstruction; no manufacturing process specified release_status: reconstruction frame: origin: >- On the cylinder axis at the nominal unfilleted leading-edge plane x = 0. The circular-arc chord runs from this plane to x = bumpChord; the actual leading blend starts upstream of the origin. Preserve the surface table's x coordinate without translating either end cap to zero. axes: x: Along the cylinder axis, positive downstream, matching the table's X column. y: >- Radially outward in the chosen meridian plane z = 0, matching the table's positive Y radius after scaling. It is a radius, not a full diameter. z: >- Perpendicular to x and y with +z = +x cross +y, completing a right-handed frame. The part is axisymmetric; no physical azimuth is specified. datums: - name: axis description: Line y = z = 0; axis of the full 360 deg revolution. - name: leadingChordPlane description: Plane x = 0, containing the origin and nominal unfilleted leading edge. - name: trailingChordPlane description: Plane x = bumpChord = 203.2 mm; sharp arc-to-cylinder join. - name: upstreamCap description: Planar disk at x = upstreamX = -650.0073203536 mm; outward normal -x. - name: downstreamCap description: Planar disk at x = downstreamX = 900.0029136304 mm; outward normal +x. envelope: min: [-650.0073203536, -95.25, -95.25] max: [900.0029136304, 95.25, 95.25] tolerance: 0.05 parameters: - name: cylinderDiameter value: 152.4 unit: mm provenance: stated source: 'sources/nasa-atb-bump-spec.md, Geometry (as built): "Cylinder diameter d = 6 inches."' tolerance: 0.01 description: >- Cylinder diameter, 6 * 25.4 mm. Changing it offsets the entire meridian radially by half the diameter change; bumpHeight remains measured above the cylinder and the two axial extents remain fixed. edit_test: delta: 2.0 expect: volume_delta: 763576.894948 direction: increase tolerance_rel: 0.002 bbox_delta: [0, 2, 2] - name: bumpChord value: 203.2 unit: mm provenance: stated source: 'sources/nasa-atb-bump-spec.md, Geometry (as built): "Bump chord c = 8 inches (axial length of the circular-arc bump)."' tolerance: 0.01 description: >- Nominal circular-arc chord, 8 * 25.4 mm, occupying x = 0 to x = bumpChord. This is not the 1550.010233984 mm endpoint span called chord by the generic profile ingest. Axial extent constants are already converted to mm. - name: bumpHeight value: 19.05 unit: mm provenance: stated source: 'sources/nasa-atb-bump-spec.md, Geometry (as built): "Bump height t = 3/4 inch above the cylinder radius."' tolerance: 0.01 description: >- Maximum radial rise, 0.75 * 25.4 mm, at x = bumpChord / 2. Recompute the main circle radius and leading-blend tangencies when edited; keep cylinderDiameter, bumpChord, filletRadius, upstreamX and downstreamX fixed. edit_test: delta: 1.0 expect: volume_delta: 82804.040776 direction: increase tolerance_rel: 0.002 bbox_delta: [0, 2, 2] - name: filletRadius value: 183.0 unit: mm provenance: inferred source: sources/nasa-atb-bump-spec.md, Geometry (as built), competing R2 values tolerance: 1.0 rationale: >- Use the explicitly directed 18.30 cm interpretation, converted to 183.0 mm. Classification is inferred because the supplied historical references also list 20.32 cm = 203.2 mm. The 1 mm digital radius tolerance is deliberately wider than the 0.01 mm stated-dimension tolerances; the discrete alternate remains an open question, not permission to change the nominal geometry. description: >- Radius of the upstream concave circular blend, tangent to the cylinder and externally tangent to the main bump circle. No downstream fillet is allowed. - name: upstreamX value: -650.0073203536 unit: mm provenance: measured (reference model) source: reference/profile.json, measurements.bbox_min[0] and points_mm[0][0] tolerance: 0.01 description: >- Signed upstream end-cap coordinate. Source X/c = -3.198854923 multiplied by the fixed source normalization 203.2 mm. Do not scale profile.json again. - name: downstreamX value: 900.0029136304 unit: mm provenance: measured (reference model) source: reference/profile.json, measurements.bbox_max[0] and points_mm[-1][0] tolerance: 0.01 description: >- Signed downstream end-cap coordinate. Source X/c = 4.429148197 multiplied by the fixed source normalization 203.2 mm. Do not scale profile.json again. features: - id: fullRevolution kind: revolve count: 1 parameters: [cylinderDiameter, bumpChord, bumpHeight, filletRadius, upstreamX, downstreamX] description: >- Close a meridian from the outer radius to the axis at each axial limit and revolve 360 deg about +x into one filled, connected solid. The axial baseline has radius cylinderDiameter / 2, with continuous upstream and downstream cylindrical portions. No bore, shell, cavity, sector gap or internal end partition is present. STEP and STL must describe this same body. verify: - method: bbox - method: solid points: [[-400, 0, 0], [0, 0, 0], [400, 0, 0]] note: Axis points confirm a filled body rather than a tube. - method: section section: upstreamCylinder - method: section section: downstreamCylinder - method: section section: axialMeridian - method: count section: axialMeridian count: 1 note: One connected outer section loop with no inner loops. - id: circularArcBump kind: profile parameters: [cylinderDiameter, bumpChord, bumpHeight, filletRadius] description: >- Main convex arc has R1 = (bumpHeight^2 + bumpChord^2 / 4) / (2 * bumpHeight) = 280.458333333333 mm and center (bumpChord / 2, cylinderDiameter / 2 + bumpHeight - R1) in the x-radius meridian. Retain its upper branch from the leading-blend tangent to x = bumpChord. Its maximum radius is 95.25 mm at x = 101.6 mm. R1 and all tangencies must be computed from the exposed parameters, not frozen as additional literal contract parameters. verify: - method: bbox - method: solid points: [[101.6, 90, 0], [101.6, 0, 90], [101.6, -90, 0], [101.6, 0, -90]] note: Four radial directions within the bump, each 5.25 mm below its crown. - method: section section: forwardArc - method: section section: bumpCrown - id: leadingBlend kind: fillet parameters: [cylinderDiameter, bumpChord, bumpHeight, filletRadius] description: >- Circular meridian blend, not an arbitrary three-dimensional edge fillet. With r = cylinderDiameter / 2, c = bumpChord, t = bumpHeight, f = filletRadius, R = (t^2 + c^2 / 4) / (2*t), d = sqrt(2*(R+f)*t-t^2), a = c/2-d and j = a+f*d/(R+f), use radius r+f-sqrt(f^2-(x-a)^2) for a <= x <= j. The blend center is (a,r+f), start is (-29.909923579934,76.2), and end is (22.017756395169,83.722035422098) mm. It is tangent at both ends and replaces the nominal leading part of the bump circle. verify: - method: solid points: [[10, 78, 0]] note: >- This point lies above the bare cylinder and inside the leading blend; its distance to the inferred blend wall is 2.543100 mm, exceeding the 1 mm filletRadius tolerance. - method: section section: leadingBlendUpstream - method: section section: leadingChord - id: sharpTrailingJoin kind: profile parameters: [cylinderDiameter, bumpChord, bumpHeight] description: >- At x = bumpChord the main arc meets the radius-76.2 mm cylinder without a trailing-edge fillet. The nominal meridian slope changes from -(bumpChord/2)/(R1-bumpHeight) = -0.388663967611 to 0. Preserve this circular sharp edge. The approximate table's rounded trailing region is not the authoritative construction here. verify: - method: section section: beforeTrailingJoin - method: section section: afterTrailingJoin - method: solid points: [[202, 70, 0], [204, 70, 0]] - id: upstreamEndCap kind: other parameters: [upstreamX, cylinderDiameter] description: Planar circular end disk named upstreamCap, outward normal -x, centered on the axis. verify: - method: face face: upstreamCap - method: solid points: [[-640, 0, 0]] - id: downstreamEndCap kind: other parameters: [downstreamX, cylinderDiameter] description: Planar circular end disk named downstreamCap, outward normal +x, centered on the axis. verify: - method: face face: downstreamCap - method: solid points: [[890, 0, 0]] interfaces: [] acceptance: bbox_tolerance: 0.05 volume: expected: 29664257.630154 tolerance_rel: 0.001 provenance: derived note: >- Define r=cylinderDiameter/2, c=bumpChord, t=bumpHeight, f=filletRadius, u=upstreamX, v=downstreamX, R=(t^2+c^2/4)/(2*t), h=c/2, b=r+t-R, d=sqrt(2*(R+f)*t-t^2), a=h-d, j=a+f*d/(R+f). The radius rho(x) is r on [u,a], r+f-sqrt(f^2-(x-a)^2) on [a,j], b+sqrt(R^2-(x-h)^2) on [j,c], and r on [c,v]. V = pi * integral(u,v,rho(x)^2 dx), evaluated analytically on all four intervals and independently checked by numerical quadrature. This is a filled solid; the profile ingest's area is not its volume or section area. surface_area: expected: 797417.539677 tolerance_rel: 0.001 provenance: derived note: >- With rho(x) defined in volume.note, S = 2*pi*integral(u,v, rho(x)*sqrt(1+rho'(x)^2) dx) + 2*pi*r^2. Integrate each smooth interval separately. Includes both planar end disks; the sharp join has zero area. center_of_mass: expected: [123.829056217831, 0, 0] tolerance: 0.05 provenance: derived note: >- Uniform geometric centroid, independent of any selected density: xbar = pi*integral(u,v,x*rho(x)^2 dx)/V with rho and V from volume.note; ybar = zbar = 0 by the full rotational symmetry. solid_count: 1 sections: - id: upstreamCylinder plane: x at: -400 expect: area: 18241.469247510 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: Filled disk on the upstream cylinder; area = pi*(cylinderDiameter/2)^2. - id: leadingBlendUpstream plane: x at: -10 expect: area: 18765.272872550 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: Leading blend upstream of nominal chord; area = pi*rho(-10)^2, rho = 77.286298088788 mm. - id: leadingChord plane: x at: 0 expect: area: 19438.680527848 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: Blend at the origin plane; area = pi*rho(0)^2, rho = 78.660817351350 mm. - id: forwardArc plane: x at: 50 expect: area: 25709.015640963 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: Main circular arc forward of crown; area = pi*rho(50)^2, rho = 90.462333833326 mm. - id: bumpCrown plane: x at: 101.6 expect: area: 28502.295699234 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: Maximum-radius disk at bumpChord/2; area = pi*(cylinderDiameter/2+bumpHeight)^2. - id: beforeTrailingJoin plane: x at: 202 expect: area: 18463.929012381 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: Arc 1.2 mm before the sharp join; area = pi*rho(202)^2, rho = 76.663232011419 mm. - id: afterTrailingJoin plane: x at: 204 expect: area: 18241.469247510 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: Cylinder 0.8 mm after the sharp join; area = pi*(cylinderDiameter/2)^2; excludes the table's trailing smoothing. - id: downstreamCylinder plane: x at: 400 expect: area: 18241.469247510 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: Filled disk well downstream; area = pi*(cylinderDiameter/2)^2. - id: axialMeridian plane: z at: 0 expect: area: 241504.064289478 area_tolerance_rel: 0.001 loops: 1 holes: 0 description: >- Entire material section through the axis, containing both positive and negative radial sides; area = 2*integral(upstreamX,downstreamX,rho(x) dx). faces: - name: upstreamCap plane: x at: -650.0073203536 normal: '-' area: 18241.469247510 area_tolerance_rel: 0.001 tolerance: 0.01 center: [0, 0] mode: one - name: downstreamCap plane: x at: 900.0029136304 normal: '+' area: 18241.469247510 area_tolerance_rel: 0.001 tolerance: 0.01 center: [0, 0] mode: one deviation: null blockout: volume_min: 30605031.757600 volume_max: 30727697.215547 export_volume_tolerance_rel: 0.002 references: - path: sources/nasa-atb-bump-spec.md kind: text role: authoritative sha256: f773288693cfbcd96bc113422d051fd3f47b86791ad0c254f7c704e99ce86165 units: in for cylinder and bump dimensions; cm for the competing fillet radii revision: Unversioned supplied specification; exact snapshot identified by SHA-256 note: >- Governs the inch-native dimensions, analytic arc, selected leading fillet, sharp trailing join, frame, solid count and cap requirement. NASA links inside the supplied text are citations, not separately ingested files. - path: sources/bumpgrd.surfpts_orig.dat kind: table role: authoritative sha256: 46f028810ad0e6e68e20520452edb44c2dfe77b42ceefa59229733d92bb15b1f units: dimensionless x/c and r/c; fixed source chord c = 203.2 mm revision: Supplied surfpts_orig snapshot; header calls the coordinates approximate note: >- 181 open meridian samples. Authoritative for axial endpoints and source normalization; intermediate samples are contextual checks, subordinate to the explicit analytic geometry and no-trailing-fillet requirement. - path: reference/profile.json kind: reference-model role: authoritative sha256: 32b04d48e80559b1e61f02b364213768d9fdee0f03423e0b29ee5bb8ca900b1c units: mm in points_mm and measurements; already scaled by 203.2 revision: 'Generated 2026-09-16T09:36:55Z' note: >- Deterministic coordinate ingest, used for the measured axial limits. source.declared_units says mm but the raw table is dimensionless; source.scale_to_mm = 203.2 is already applied in points_mm. measurements.chord is the full endpoint span, not bumpChord. The closed polygon area, centroid, perimeter and binned max_thickness are generic ingest summaries, not solid properties or governing bump dimensions. This file contains no reference mesh or suggested tolerance band. - path: reference/profile.png kind: image role: illustrative sha256: 4a9d293999dd4fa5f207270b279a6237aa144e62610cd43bee6d6b48e9a67f91 units: pixels; plot of the already scaled mm meridian revision: Companion plot to profile.json generated 2026-09-16T09:36:55Z note: >- 900 by 70 pixel plot, inspected for one raised meridian bump and the two long cylinder runs. No dimension annotations or independently calibrated scale; no parameter is inferred from its pixels. open_questions: - >- Which historical leading-edge radius is correct: 18.30 cm (183.0 mm) or the documented alternate 20.32 cm (203.2 mm)? This contract fixes the instructed inferred nominal at 183.0 mm; 203.2 mm is an unbuilt alternate. - >- What accounts for the approximate coordinate table's trailing-edge smoothing and small leading-blend differences from the specified analytic profile? The active contract uses its axial limits but retains the explicitly required sharp trailing join; it does not interpolate the rounded samples. - >- What chordal and angular tessellation tolerances does the downstream CFD workflow require for STL? No values were supplied; the retained 0.2 percent cross-format volume check alone does not establish local surface accuracy.