1) Why berthing velocity matters
Berthing impacts are typically evaluated by energy, but crews feel the outcome as speed. A small change in approach velocity can create a large change in impact energy because energy varies with velocity squared. For example, a 20% speed increase raises energy by about 44%. This calculator converts an available energy value into a recommended velocity so operational targets match design capacity.
2) Inputs that drive the result
The three biggest drivers are displacement, available energy, and the combined coefficient (Ce × Cs × Cc). Displacement is entered in tonnes and converted to kilograms internally. Energy is entered in kJ and converted to joules. Typical planning values often use added mass between 0–30%, depending on hull form and water depth conditions.
3) Added mass and hydrodynamic effects
Added mass represents extra water accelerated with the vessel during contact. The calculator uses Cm = 1 + (added mass % / 100). If displacement is 25,000 t and added mass is 10%, effective mass increases by 10% for the energy balance. This is useful when comparing calm-water berthing against more constrained or shallow-water cases.
4) Coefficients and practical ranges
Coefficients allow you to reflect approach condition, system response, and contact layout without changing the core physics. Many projects keep Ce, Cs, and Cc within about 0.7–1.2 for screening studies, then refine per specification. If your combined coefficient decreases, the allowable velocity decreases because the same energy is absorbed less effectively.
5) Safety factor and operational conservatism
The safety factor (SF) divides the calculated velocity to build margin. Values around 1.05–1.30 are common for conservative operational limits, while higher factors may be used for uncertainty. The history table stores SF with each run so you can demonstrate how a limit was selected during reviews.
6) Unit checks and conversions
Output is shown in m/s, knots, and km/h to match marine practice. This tool uses 1 knot = 0.514444 m/s and km/h = m/s × 3.6. Always confirm that the energy input reflects the same condition as the coefficients, such as the same berth face and fender arrangement.
7) Scenario comparison using history
The calculator keeps up to 25 recent scenarios in session history. This supports quick comparison such as “same vessel, different fender energy” or “same berth, different added mass.” Export to CSV for spreadsheets or share a compact PDF summary during toolbox talks and design coordination meetings.
8) Good practice notes for project records
Record the assumption set: displacement basis (loaded or ballast), the source of available energy, and the meaning of each coefficient. For operational limits, add environmental qualifiers such as wind/current thresholds and tug assistance. Treat the result as a planning target and confirm with governing standards and site procedures before field use.