PRC Naval Architecture & Marine Engineering flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Block Coefficient

Ratio of the underwater volume to the volume of a rectangular block of length L, breadth B and draught T. C_B = ∇/(L·B·T); higher values indicate fuller hull forms typical of tankers and bulk carriers.

Froude Number

Dimensionless speed parameter Fn = V/√(gL). Wave-making resistance depends primarily on Fn, so model tests and full-scale predictions compare hulls at equal Froude number.

Metacentric Height GM

Vertical distance from centre of gravity to transverse metacentre. GM = KB + BM − KG; positive GM gives initial stability, negative GM causes an unstable loll and must be avoided.

Righting Lever GZ

Horizontal distance between centre of gravity and centre of buoyancy at a given heel angle. GZ multiplied by displacement gives righting moment; the GZ curve defines stability at large angles.

ITTC-1957 Friction Line

Standard empirical formula for frictional resistance coefficient C_F = 0.075/(log10 Rn − 2)². Used to scale model resistance to full scale by subtracting model friction and adding ship friction.

Free Surface Effect

Loss of effective metacentric height caused by liquid shifting in partially filled tanks. The virtual rise of G equals ρ_liquid·i / Δ, where i is the free surface second moment of area.

Admiralty Coefficient

Empirical relation C = Δ^(2/3)·V³/P linking displacement, speed and power. A parent-ship C value allows first-pass power estimation for a new design of similar type.

Design Spiral

Iterative design process in which displacement, dimensions, form coefficients, power and weight are repeatedly recalculated until they converge to a consistent, feasible design.

Deadweight

Total weight a ship can carry at a given draught: cargo, fuel, lubricating oil, fresh water, ballast, stores, crew and effects. Deadweight plus lightship equals total displacement.

Longitudinal Framing

Framing system with continuous longitudinal stiffeners supported by widely spaced transverse webs. Efficient for resisting longitudinal bending in long ships such as tankers and bulk carriers.

Transverse Framing

Framing system with closely spaced transverse frames supported by longitudinal girders. Suited to shorter vessels and where local load resistance governs over longitudinal bending strength.

Section Modulus Check

Verification that the hull girder's midship section modulus exceeds the minimum required for combined still-water and wave-induced bending moments in both sagging and hogging conditions.

Load Line Freeboard

Minimum distance from the assigned load line to the freeboard deck, set by the International Convention on Load Lines and adjusted for block coefficient, superstructure and sheer.

Hogging and Sagging

Hogging is excess buoyancy amidships causing the hull to bend upward at the ends; sagging is the reverse. Both create longitudinal bending stresses checked in hull girder strength analysis.

Uniflow Scavenging

Scavenging method in large two-stroke diesels where air enters through ports at the cylinder liner bottom and exhausts through a central valve. Gives efficient, clean scavenging.

Brake Mean Effective Pressure

BMEP = brake power × 60 / (L·A·n·k), relating engine output to cylinder volume and speed. Typical large two-stroke values are around 18–21 bar at rated output.

Specific Fuel Consumption

Fuel mass burned per unit of brake work, quoted in g/kWh at stated reference conditions and lower calorific value. Lower SFOC indicates better engine thermal efficiency.

Turbocharger Matching

Selection of turbine and compressor to match engine airflow across the load range. Mismatch causes poor scavenging, high exhaust temperature or surge at low load.

MARPOL Annex VI Sulphur Limit

Fuel sulphur cap of 0.50% m/m globally from 1 January 2020, and 0.10% m/m in Emission Control Areas. Equivalent compliance via scrubbers is permitted with approval.

NOx Tier III

Stricter nitrogen oxide emission standard for ships built on or after 1 January 2016 operating in designated ECAs. Compliance typically requires SCR or exhaust gas recirculation.

EEDI

Energy Efficiency Design Index: grams of CO2 per tonne-mile at design conditions. Attained EEDI must be at or below the required value, which tightens in phases over time.

Propeller Law

For a fixed-pitch propeller in open water, absorbed power varies approximately with shaft speed cubed and thrust with speed squared, defining the propeller load curve.

Block Assembly

Fabrication stage where panels and sub-assemblies are welded into three-dimensional hull blocks. Blocks are then outfitted and erected in the dock or building berth.

Welding Distortion Control

Use of balanced sequences, backstep welding, skip welding and pre-setting to limit angular distortion and buckling in thin-plate hull panels during fabrication.

Ultrasonic Testing

Non-destructive method using high-frequency sound to detect internal volumetric defects such as lack of fusion and porosity in thick hull welds. Acceptance follows classification rules.

Magnetic Particle Inspection

Surface and near-surface defect detection method for ferromagnetic steel using magnetisation and iron particles. Effective for finding cracks at weld toes and heat-affected zones.

Docking Plan

Drawing specifying keel, bilge and side block positions and load limits so the hull is supported without over-stressing structure during drydocking, undocking and repair.

Sea Trial Acceptance

Contractual verification of speed–power curve, turning circle, zig-zag manoeuvre, crash stop, endurance and anchor handling against the vessel's specification before delivery.

Permit to Work

Formal authorisation system controlling hot work, enclosed-space entry and other high-risk repair activities. Requires gas-freeing, atmosphere testing and defined supervision before work begins.

Classification vs Flag State

Classification societies set technical rules and issue class certificates; flag states issue statutory certificates. Roles remain legally distinct even when a society acts as recognised organisation.

ISM Code

International Safety Management Code requiring a documented safety management system covering policies, procedures, emergency preparedness and non-conformity reporting for ship operation.

Conflict of Interest Disclosure

Professional duty to declare financial or personal interests that could bias design approval, survey findings or test certification, and to withdraw from the decision if bias is likely.