METHOD OF MONITORING SHIP'S STABILITY AND SPEED Russian patent published in 2005 - IPC

FIELD: shipbuilding; monitoring stability and speed of ships in service.

SUBSTANCE: proposed method includes measurement of rolling period and estimation of metacentric height by calculations. In calculating the metacentric height, the following magnitudes shall be determined: ship's drafts fore and aft, apparent wave period, relative bearing, ship's speed in irregular waves, apparent wind velocity, air temperature and sea water temperature. In determination of speed under ice conditions, thickness of ice and thickness of snow, as well as thickness of shell plating and framing members in fore portion of ship shall be additionally determined; actual state of hull is estimated taking into account reduced thickness of plating and framing members due to wear; then, safe speed of ship's motion in unbroken and in broken ice is determined. Safe speed of ship running in unbroken ice is calculated by the following formula: v/v₀=0.95-0.50(h/h*)-0.25(h/h*)²-0.30(h_s/h**)-0.20(h_s/h**)² at full-load displacement and in ballast it is found by the following formula: v/v₀=1.0-0.63(h/h*)-0.27(h/h*)²-0.37(h_s/h**)-0.18(h_s/h**)²; during motion in broken ice behind icebreaker in standard mode, use is made of following formulae: v/v₀=0.97-0.50(h/h**)-0.25(h/h**)²+▵(v/v₀) and v/v₀=0.85-0.52(h/h**)-0.21(h/h**)² in maneuvering mode, where v₀ is ship's speed in free water, h*=0.5 is limit (standard) magnitude of ice thickness, m; h**=0.25 is standard magnitude of ice thickness, m; h_s is thickness of snow cover, m; ▵(v/v₀) is correction for reduction of speed at impact of fore section of ship against ice which is calculated by the following formulae at full-load displacement: ▵(v/v₀)=-0.31(h/h**)+(0.31(h/h*)² and(v/v₀)=-0.37(h/h*)-0.37(h/h*)² for ship in ballast within range of 0.4≤(h/h*)≤1.0; permissible speed of ship placed in protracted service is determined at wear of shell plating by the following formulae: v_t=k_δ/v₀ and v_t=k_w/v₀ in case of wear of framing members, where v₀ is ship's speed when her hull is new which is found by the following formula: v/v₀=0.95-0.50(h/h*)-0.25(h/h**)²-0.30(h_s/h*)-0.20(h/_s/h*)² or v/v₀=1.0-0.63(h/h*)-0.27(h/h*)²-0.37(h_s/h*)-0.18(h_s/h*)²; kδ=1.0-3.9[1-(δ_t/δ₀]+5.4[1-(δ_t/δ₀)]² is coefficient for proportional reduction of speed; k_w=1.0-1.6[(1-w_t/w₀)] is coefficient for proportional reduction of permissible running speed depending on degree of wear of shell plating; k_w=1.0-1.6[(1-w_t/w₀)] is coefficient for proportional reduction of permissible speed due to wear of framing members; δ_t and δ₀ are respectively thicknesses of shell plating of worn and new hulls; w_t and w₀ are moments of inertia of framing member section of worn and new hull respectively.

EFFECT: enhanced reliability of estimation of safety of ship running in ice due to monitoring her speed depending on intensity of ice load.

1 dwg