Cable Angle Research Articles

Approximate Solutions for Cables under Generalized Hydrodynamic Loadings

Approximate closed‐form solutions are given for the configuration of a cable under generalized hydrodynamic loading, in which the weight may take on any value and the drag is composed of arbitrary proportions of friction and pressure components. The basis of the approximation is a set of solutions for a cable with nonzero weight under pure friction drag. It is shown that by using a simple asymptotic matching of these solutions with the exact value of the cable critical angle at large cable lengths, reasonable approximations are obtained for cables under a more general drag loading. The accuracy is further increased by replacing the actual weight‐to‐drag ratio by an effective ratio, which accounts for the drag loading through the critical angle. The resulting solutions are highly accurate (to better than two places) for cases in which the initial and critical angles lie in the same quadrant, and furnish useful estimates when these angles lie in different quadrants.

Cable Recovery With Overrun

Cable is normally recovered by hauling in from ahead, with the cable guiding the ship. In an early paper, Zajac presented a method for recovery, proposed by Shea, in which the cable is overrun, and hauled in tending aft. The potential advantage is lower tension in recovery. Cable was recovered with overrun in two recent exercises. The tensions and cable angles observed at the ship in these exercises are used to work out cable configurations and bottom tensions. The calculations show that the bottom tension was considerably less than it is for normal recovery in both exercises. As the overrun is increased, the tension decreases, and tends to a limiting value defined by the ship speed and the slack rate at which the cable was originally laid. Recovery with overrun is practical and advantageous.

Comparative steady state deep towing performance of bare and faired cable systems

Abstract The measured drag characteristics of a variety of cable fairings are reviewed and compared with those of bare cables. The effect of cable inclination angle has been studied and an empirical rule developed for dealing with faired cables, the hydrodynamic properties of which are shown to depend significantly on the section shape of the fairing. Non-dimensional cable functions are tabulated for both bare and faired cable profiles and applied to show how the addition of fairings can improve the towing performance of a given system. Simple formulae are developed for calculating faired cable system properties and for assessing the effect of fish drag on the depression angle.

Predicting the equilibrium depth of a body towed by a faired cable

Comprehensive wind tunnel measurements have been made of the drag coefficients of both the body and the faired cable of a towed system. The drag data has been embodied in theoretical calculations of the depth attained in tow, at speed up to 3 m s −1 (6 knots) with scopes up to 135 m (440 ft). The agreement with sea trial observations is excellent. The work has highlighted the importance of accounting for the variation of faired cable drag with cable angle and has shown that the drag increments due to gaps and misalignments between individual fairing elements cannot be ignored. Methods are derived for estimating these effects for application to other faired cable towed systems.

The measurement of gustiness in the first few thousand feet of the atmosphere

A description is given of instruments which have been designed and used to measure gustiness, in the form of inclination and total speed of the wind, from a position on the cable of a captive balloon. A lightweight wind vane with automatic compensation for tethering cable angle, and a sensitive vane airmeter are used as sensing heads. The data, with reference signals, are relayed by electric cable to ground level and recorded on multi-channel recorders. Both instruments have good response to wind fluctuations with periods down to one second. A brief account is given of some observations made at Cardington, Beds., and some examples are presented of records made at 1,000, 2,000 and 3,000 ft in contrasting meteorological conditions.

The measurement of gustiness in the first few thousand feet of the atmosphere

AbstractA description is given of instruments which have been designed and used to measure gustiness, in the form of inclination and total speed of the wind, from a position on the cable of a captive balloon. A lightweight wind vane with automatic compensation for tethering cable angle, and a sensitive vane airmeter are used as sensing heads. The data, with reference signals, are relayed by electric cable to ground level and recorded on multi‐channel recorders. Both instruments have good response to wind fluctuations with periods down to one second.A brief account is given of some observations made at Cardington, Beds., and some examples are presented of records made at 1,000, 2,000 and 3,000 ft in contrasting meteorological conditions.