The table below shows performance of the 3 types of AnSlope mooring, with and without current loading. The analysis employed a moderate current profile - 60 cm/sec at 200 m, diminishing linearly to 20 cm/sec at 1600 m. Mooring types A, B, and C are set in 800 m, 1200 m, and 1600 m of water, respectively. Moorings in the Center array are like those in the West and East arrays, with addition of a T/P recorder at 200 m.
| Type A mooring (West, East) | Type A mooring (Center) | Type B mooring (West, East) | Type B mooring (Center) | Type C mooring (West, East) | Type C mooring (Center) | |
|---|---|---|---|---|---|---|
| tension at anchor (no current) | 875 lb | 965 lb | 854 lb | 944 lb | 1002 lb | 1092 lb |
| tension at anchor (moderate current) | 876 lb | 945 lb | 849 lb | 918 lb | 987 lb | 1055 lb |
| wire angle at anchor (moderate current) | 15 deg | 18 deg | 19 deg | 21 deg | 17 deg | 19 deg |
| depth of top instr (no current) | 400 m | 200 m | 400 m | 200 m | 400 m | 200 m |
| depth of top instr (moderate current) | 412 m | 252 m | 439 m | 285 m | 457 m | 313 m |
Note that in most cases, line tension at the anchor decreases under current loading - not an intuitive result. The explanation is that with a nonzero current, drag forces pull the mooring over and a component of the buoyancy acts normal to the line to balance the normal component of drag (which pulls in the opposite direction). The resulting decrease in buoyancy along the line is greater than the increase in drag along the line.
These numbers were obtained with a computer program named MOORAN that the OSU Buoy Group has used for many years. MOORAN is available on request.
Return to the previous page.