Hydrodynamic Loads on Twisted Ropes and Hawsers

Abstract

The loads on both a model of a smooth cable and a helical strake (also known as scrouton spiral) were measured in a wind tunnel. The coefficients of drag, lift and transverse force were ascertained for an angle of attack between 0 and 360 degrees. Results show that the drag coefficient increases by the spiral in each case whereas the lift coefficient changes only insignificantly. A defined transverse force is caused by the spiral. To find an explanation of this force by the circulation a simple mathematical model is given. Finally the behaviour of a twisted rope in water calculated by a known code is predicted in case of steady current.

Performance of an Active Stimulating Device Using a Rope Kite or Array in the Cod End to Reduce Juvenile by-catch

“…Based on previous data on drag and lift coefficients of a circular cylinder (Schlichting, 1979;Norberg, 2003;Winkel and Paschen, 2005;Gavalda et al, 2009;Vaikil and Green, 2009), the coefficients for the braided PA ropes used in this experiment (diameter 3-12 mm) with surface roughness, an aspect ratio of 10, and a Reynolds number of 1.5´10 5 were estimated at C D =0.1 at α=0°, C D =1.0 at α=90°, C L /C D =0.05 at α=0°, and C L /C D =0.5 at α=45°. Next, slopes for Eqs.…”

“…Coefficients C D and C L are functions of Reynolds number, angle of attack (α), aspect ratio (l/d), surface roughness, fluctuation, etc., derived from the circular cylinder cases (Schlichting, 1979;Chakroun et al, 1996;Winkel and Paschen, 2005). To simplify the braided rope, coefficients were assumed to change linearly with the angle of attack as follows:…”