Propeller Cavitation, Tip Speed, Pressure Margin & Blade Erosion Risk Tool | ShipUniverse
ITTC 2024 Cavitation Framework • σn / σv • Tip Speed • Pressure Margin • Blade Loading • Erosion Risk • Operating Envelope

Propeller Cavitation, Tip Speed, Pressure Margin & Blade Erosion Risk Tool

Screen a propeller operating point for cavitation inception margin, local pressure margin, tip speed, blade loading, immersion, observed cavitation behaviour and erosion exposure. The tool separates hydrodynamic screening from model-test, CFD, class and maker acceptance so an apparently comfortable RPM or tip speed cannot create a false “cavitation-free” conclusion.

Propeller & Vessel Basis

Use approved propeller particulars where available. Tip-speed and cavitation acceptance limits are design-specific, not universal statutory values.

m.
For CPP, use the effective P/D at the entered pitch condition.
m below mean local water surface.
m, nearest hull / structure clearance.
% of diameter. User-entered screening criterion.
r/R for cavitation pressure reference, often 0.7R to 0.9R in testing practice.

Operating Point

rpm.
knots.
Used for VA = VS(1-w).
kN.
kW delivered to the propeller shaft.
m deducted from local blade submergence.

Advanced Operating Profile

Compare design, ballast, heavy-weather, maneuvering and other operating points. The global propeller geometry and screening criteria apply to every row.

ConditionRPMSpeed knWakeThrust kNShaft depth mWater °CImmersion loss mHours/yrObserved cavitation

Water & Pressure Environment

°C. Used for water vapour pressure.
kg/m³.
kPa absolute.
Multiplier on freshwater vapour pressure. Keep vessel/project basis if known.
% screening indicator for highly non-uniform inflow.
kPa peak-to-peak, optional monitoring/model-test input.
kPa. User-entered criterion, not a universal rule.

Cavitation Design / Model-Test Criteria

These criteria are intentionally user-entered. ITTC defines standard cavitation-number relationships and test procedures, but there is no universal cavitation-inception or erosion number that is valid for every propeller and wake field.

From model test, CFD correlation, maker/design data or approved project study.
% owner/design margin above the entered inception σn.
Magnitude from CFD/model/design. Enter 0 to disable the Cp pressure-margin screen.
m/s. Enter maker / owner / project limit.
User-entered limit for T / (0.5ρVref²AE).
kPa above vapour pressure after the entered |Cp|min estimate.

Observed Cavitation & Blade Condition

cm² across observed blade damage.
mm.

Efficiency / Repair Economics

t/year.
$/t or selected accounting currency basis.
% attributed to roughness / erosion / off-design propeller condition.
% after the proposed inspection/repair/operational intervention.
Engineering limitation: This is a screening and operating-envelope tool, not a propeller design approval, class calculation or substitute for a cavitation tunnel test, CFD analysis, wake survey, propeller maker limits, vessel vibration investigation or underwater/full-scale cavitation observation. ITTC's 2024 erosion guidance explicitly notes that there is no universally accepted hydrodynamic method for determining erosion risk. Local wake peaks, cavitation nuclei, gas content, blade geometry, scale effects, roughness, damage and unsteady inflow can materially change real cavitation behaviour.
Engineering basis: ITTC Recommended Procedures and Guidelines 7.5-02-03-03.1, Model-Scale Cavitation Test (2024); 7.5-02-03-03.2, Visual Description and Measurement of Cavitation Events (2024); and 7.5-02-03-03.5, Cavitation Induced Erosion on Propellers and Rudders, Model Scale Experiments and Numerical Guidance (2024). ITTC defines cavitation numbers including σv = (pa-pv)/(0.5ρV²) and σn = (pa-pv)/(0.5ρn²D²), and emphasizes representative wake, static pressure, water temperature, gas content, visual cavitation behaviour and correlation with erosion observations. DNV's July 2025 ship-rule edition, effective 1 January 2026, included revised propeller assessment methods. Project-specific class, maker and design documentation controls acceptance.
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