Torsional Vibration Analysis
Standard marine TVA: mass-elastic modelling, natural frequencies, mode shapes, harmonic excitation and forced response across the operating speed range.
Torsional vibration analysis · TVA
Torsional dynamics for marine propulsion
Simulation and class-review-ready torsional vibration analysis for conventional, electric and hybrid propulsion systems.
- DNV · Lloyd's Register calculations
- Frequency- & time-domain simulation
- Developers of OpenTorsion
The core question
Is your propulsion drivetrain dynamically safe throughout its operating envelope?
Engines, motors, couplings, gearboxes, shafts and propellers form one torsional system with inertia, stiffness and damping. Excitation from engines, electric machines, propellers, waterjets or ice can drive it into resonance. We find out where, and what to change.
01Where are the torsional natural frequencies?
02Are there resonances in the operating range?
03What vibratory torques and shaft stresses occur?
04Is a barred speed range required?
05Is the selected flexible coupling suitable?
06What if the gear ratio, engine or propeller changes?
07How does an electric motor or PTO/PTI affect the system?
08What happens during a transient or propeller–ice impact?
09Does the design satisfy the classification requirements?
Services
We simulate torsional vibration in marine propulsion systems.
You design the vessel and propulsion system. We handle the torsional dynamics — from the first mass-elastic model to the report that goes to class.
Class Calculations
Class-review-ready TVA calculations and documentation for DNV and Lloyd's Register, including revisions in response to class comments.
Design & Optimisation
Parameter sweeps and sensitivity studies to compare propulsion configurations and find the coupling, inertia or ratio that moves resonances out of the way.
Transient Analysis
Time-domain simulation of non-steady operation: start-up and shutdown, clutch engagement, generator connection, motor torque transients and fault conditions.
Ice-Class Analysis
Simulation of propeller–ice interaction and the resulting transient shaft torque, component loads and vibratory stress for ice-going vessels.
Special Drivetrain Studies
Electric, hybrid, PTO/PTI, waterjet and unusual propulsion architectures — including highly coupled and nonlinear systems.
Typical TVA scope
Propulsion arrangements
Vendor-independent. The analysis is not tied to any engine, gearbox, coupling or propulsion supplier.
Beyond pass / fail
Design changes that remove resonances
Analysis is most valuable while components can still change. We evaluate coupling stiffness, inertias, shaft dimensions, gear ratio and operating speed to show which change actually fixes the problem — before hardware is ordered.
- Coupling stiffness & inertia
- Flywheel, motor and generator inertia
- Shaft diameter, length & material
- Gearbox ratio & operating RPM
- Propeller inertia & control strategy
Typical finding
“A resonance occurs at 720 rpm.”
Our finding
“A resonance occurs at 720 rpm. Increasing the coupling compliance moves the corresponding natural frequency below the continuous operating range.”
Ice-going vessels
Ice-class torsional analysis
We analyse the transient loads from propeller–ice interaction with both time-domain simulation and frequency-domain methods — a particular strength for Nordic and other ice-going vessel projects.
- Ice-induced transient shaft torque
- Drivetrain response to ice impact sequences
- Maximum shaft and component torque
- Vibratory stress & fatigue-related load assessment
- Drivetrain alternatives compared under ice loading
When to call us
Even a small change can shift a natural frequency.
If any of these are on your desk, a torsional calculation is probably too.
- New vessel
- New propulsion design
- Class requesting TVA
- Class comments on a TVA
- New engine or electric motor
- Engine replacement
- Repowering
- Gearbox replacement
- Coupling selection
- Coupling replacement
- Propeller replacement
- Waterjet propulsion
- Shaftline modification
- Power increase
- Hybridisation
- Electrification
- PTO/PTI installation
- Alternative-fuel conversion
- Ice-class vessel
- Unusual drivetrain architecture
- Resonance problem
- Component failure
Process
How a project works
No lengthy questionnaire. Tell us about the case, we agree the scope in a short technical discussion, and you receive a clear proposal. Projects are delivered fully remotely — no vessel visit required.
-
01
Tell us about the project
A short description of the vessel, propulsion system or problem. No documents needed at this stage.
-
02
30-minute technical meeting
We establish what you are designing, which calculations and class rules apply, what data exist and when you need results.
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03
Proposal
Simulation scope, applicable rules, required input data, deliverables, design alternatives, included revisions, schedule and price.
A Simulation model
Mass-elastic representation of the full drivetrain: engine, crankshaft, flywheel, coupling, gearbox, shafts, motors, generators, PTO/PTI, propeller or waterjet.
B Calculation results
Natural frequencies, mode shapes, Campbell diagrams, vibratory torque, torsional stress, critical speeds, barred speed ranges, time histories and sensitivity results.
C Engineering assessment
Not just graphs. Which mode is responsible, what excitation drives it, whether limits are exceeded — and what changes improve the design.
D Class-review-ready report
Professional PDF documenting requirements, methodology, assumptions, component data, results, limits, barred speed assessment and conclusions.
Standard TVA
Quoted per project
Scope sets the price, and a simple project stays simple to buy. A standard analysis includes:
- Model construction
- Natural frequency analysis
- Frequency-domain forced response
- Engineering assessment
- Class-review-ready report
- Normal project communication
Priced separately when needed
Framework agreements available for recurring work — shipyards, integrators, engineering offices and component manufacturers.
Open source
We develop OpenTorsion.
Our team develops OpenTorsion, the open-source Python library for torsional vibration modelling and analysis. It's publicly inspectable proof of how we model drivetrains — finite element shaftline models, natural frequencies, eigenmodes, forced response and time-stepping simulation.
OpenTorsion is the technical foundation. Next comes a professional torsional vibration analysis tool built on the same experience: graphical shaftline modelling, component libraries, class-rule checks and automated reporting.
import opentorsion as ot
# Engine, coupling hub and propeller as lumped inertias
disks = [
ot.Disk(0, I=1.2e3),
ot.Disk(1, I=85.0),
ot.Disk(2, I=2.4e3),
]
shafts = [
ot.Shaft(0, 1, None, None, k=4.1e6, I=0),
ot.Shaft(1, 2, None, None, k=9.8e6, I=0),
]
assembly = ot.Assembly(shaft_elements=shafts, disk_elements=disks)
lam, modes = assembly.undamped_modal_analysis()
ot.Plots(assembly).plot_eigenmodes(modes=2)Who we work with
Torsional analysis without an in-house specialist
For teams that need torsional vibration calculations regularly — but not often enough to justify a dedicated internal specialist.
Ship design offices & naval architects
You design the vessel and shaftline. We perform the TVA and prepare the class calculation.
Shipyards
Newbuild and retrofit yards needing class TVA once engine, gearbox, coupling, shaftline and propeller are selected.
Propulsion system integrators
You deliver the propulsion package; we are the torsional specialist on every project.
Engine & motor manufacturers
Application engineering, unusual installations, hybrid and electric arrangements, independent analysis.
Gearbox & coupling manufacturers
Coupling selection, stiffness optimisation, gearbox integration and component load calculation.
Waterjet manufacturers
Complete engine–gearbox–shaft–waterjet drivetrain dynamics, including transients.
Engineering consultancies
We act as the specialist subcontractor for the torsional part of your design project.
Shipowners & fleet operators
Repowering, retrofits, drivetrain failures, operating restrictions and independent assessments.
We do
Model and simulate the drivetrain.
Where measurement data already exist, we can use them as input or for comparison against simulation.
We don't
Perform mechanical or measurement work onboard.
No shaft installation, alignment or vibration measurements, condition monitoring, balancing, repair, commissioning or inspection.
The engineers
Founders
Marine Engineering Dynamics is run by its two founders. The engineer who scopes your case is the engineer who builds the model and signs the report. There is no handover to a junior team.
Dr. Sampo Laine
Co-founder · D.Sc. (Tech.), rotordynamics
Doctorate in rotordynamics, lateral and torsional, covering bearing, support and foundation modelling and fluid–rotor interaction. Lead contributor to OpenTorsion, the open-source torsional finite element library from Aalto University's Arotor group. Writes much of our simulation code: finite element models, spectral methods in Python, and simulation of electric drives and power electronics.
LinkedIn
Dr. Tuomas Tiainen
Co-founder · D.Sc. (Tech.), mechanical engineering
Mechanical engineer with a strong background in software engineering, and a contributor to OpenTorsion. Builds the tooling that turns repeated calculation work into reviewable analysis: model assembly, parameter sweeps and report generation. Also works on drivetrain modelling for conventional, electric and hybrid propulsion.
LinkedInContact
Request a quote
Send us a short description of the propulsion system or calculation you need. We will review the case and get back to you to arrange a technical discussion.