[campbell-basic] Campbell Diagram

[MarkusNeusinger]

Plot Request: Campbell Diagram

A Campbell Diagram (also called interference diagram) plots natural frequencies against rotational speed to identify critical speeds and resonance conditions in rotating machinery.

Key Features

• X-axis: Rotational speed (RPM or Hz)
• Y-axis: Frequency (Hz)
• Multiple natural frequency lines (mode shapes) across the speed range
• Engine order lines (1×, 2×, 3×, etc.) as diagonal lines from origin
• Intersections highlight critical speeds / resonance crossings
• Optional: color-coded or labeled mode shapes, highlighted critical speed zones

Applications

• Rotordynamics and vibration analysis
• Turbomachinery design (turbines, compressors, pumps)
• Automotive powertrain (engine/transmission NVH)
• Structural dynamics of rotating equipment

Visual Reference

https://www.researchgate.net/figure/Campbell-Diagram-of-the-Seat-rail-acceleration-direction-Y_fig6_304009601

Data

• Synthetic rotordynamic data with 4-5 natural frequency curves
• 3-4 engine order excitation lines (1×, 2×, 3×)
• Critical speed intersection markers

[claude]

✅ Spec ID: campbell-basic

Rationale: Campbell Diagrams are a well-established engineering visualization for rotordynamics — no existing spec covers this plot type. The combination of natural frequency curves, engine order lines, and critical speed markers makes this a distinct and useful addition.

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[github-actions]

✅ Specification Ready: campbell-basic

PR: #4242

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specification.md

campbell-basic: Campbell Diagram

Description

A Campbell Diagram (also called an interference diagram) plots natural frequencies against rotational speed to identify critical speeds and resonance conditions in rotating machinery. It overlays engine order excitation lines (diagonal lines from the origin) on top of natural frequency curves, with intersections marking critical speeds where resonance may occur. This visualization is essential for ensuring safe operating ranges in turbomachinery, automotive powertrains, and other rotating equipment.

Applications

• Rotordynamic analysis of turbomachinery (turbines, compressors, pumps) to identify critical speeds that must be avoided during operation
• Automotive powertrain NVH (Noise, Vibration, Harshness) engineering to map engine order excitations against structural modes
• Vibration analysis of rotating equipment during design validation to ensure natural frequencies are sufficiently separated from operating speed excitations

Data

• speed (numeric) - Rotational speed in RPM, evenly spaced across the operating range (e.g., 0-6000 RPM)
• frequency_mode_N (numeric) - Natural frequency in Hz for each mode shape (4-5 modes), varying with rotational speed
• engine_order (numeric) - Integer multipliers (1x, 2x, 3x) defining diagonal excitation lines from the origin
• critical_speeds (numeric) - RPM values where engine order lines intersect natural frequency curves
• Size: 50-100 speed points per mode, 4-5 natural frequency curves, 3 engine order lines, 6-10 critical speed markers

Notes

• Engine order lines are straight diagonal lines from the origin with slope = order_number / 60 (converting RPM to Hz)
• Natural frequency curves should show realistic behavior: slight variation with speed due to gyroscopic effects (some modes increase, some decrease with speed)
• Critical speed intersections should be marked with distinct markers (e.g., red circles or diamonds)
• Mode shapes should be labeled (e.g., "1st Bending", "2nd Bending", "1st Torsional", "Axial")
• Engine order lines should be labeled (e.g., "1x", "2x", "3x")
• Use a clean legend distinguishing natural frequency curves from engine order lines
• Optional: shade or highlight critical speed zones around intersection points

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[github-actions]

🚀 Specification Merged!

Specification: campbell-basic
PR: #4242 (merged)

The specification is now in main and synced to PostgreSQL.

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Available libraries: matplotlib, seaborn, plotly, bokeh, altair, plotnine, pygal, highcharts, letsplot

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