Ship Froude Number & Resistance Calculator
Naval hydrodynamics: Calculate length & volumetric Froude numbers, ITTC-1957 friction line, wave-making drag, and effective propulsion power (P_E).
Vessel Hull & Speed Parameters
Hydrodynamic Resistance & Power
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
What is the significance of the Froude number in ship design?
The Froude number (Fn = V / sqrt(g * L)) governs dynamic wave similarity. For Fn < 0.25, frictional resistance dominates (70-85% of total drag). Between Fn = 0.28 and 0.35, the hull encounters the main wave-making hump where transverse waves generated at the bow reinforce at the stern, causing drag to spike. Beyond Fn = 0.40, a displacement hull cannot climb over its bow wave without dynamic lift (planing).
How does the ITTC-1957 line determine ship frictional resistance?
The International Towing Tank Conference (ITTC-1957) model-ship correlation line expresses flat-plate friction coefficient as C_F = 0.075 / (log10(Re) - 2)^2. This friction coefficient is scaled by the 3D hull form factor (1+k) to account for three-dimensional velocity augment and boundary layer thickening around curved ship hulls.
What is effective power (P_E) versus delivered shaft power (P_D)?
Effective power (P_E = R_T * V) is the theoretical towrope power required to pull the bare ship through calm water at speed V. The actual engine shaft power (P_S) or delivered power (P_D) must be significantly higher (typically P_E / 0.65 to P_E / 0.75) to compensate for propeller open-water efficiency, hull-propeller interaction (wake fraction w, thrust deduction t), and shaft transmission losses.