ABSTRACT 



Two alternative methods for predicting steady- state configurations 

 and towline tensions are evaluated by comparing predicted data with 

 experimental data. Between the two methods, Method 1 is shown to 

 provide better overall predictions of cable tension, cable angle at towing 

 ship, and body depth for the bare-cable case. The best agreement 

 between the experimental data and the data predicted by Method 1 is 

 obtained with a cable drag coefficient of 1 . 5 and a tangential force factor 

 of 0.02. 



INTRODUCTION 



The David Taylor Model Basin is engaged in a broad research program 

 directed toward the development of improved experimental and analytical 

 techniques for predicting the steady-state and dynamic characteristics 

 of cable-towed systems. Pursuant thereto, a project was initiated to 

 determine which of the various existing methods would provide the most 

 accurate predictions of the steady-state configurations and associated 

 towline tensions for cable-towed bodies. The project is being carried 

 out in two phases; one involving the use of bare cables and the other 

 involving the use of faired cables. This report deals with the first phase, 

 and is confined to an evaluation of the two methods most commonly used 

 by the Model Basin. The investigation was carried out in conjunction 

 with Bureau of Ships Subproject S-F006 03 02, Task 7462. 



The need for improved towing capabilities and the requirements for 

 cable-towed-sonar, detection, surveillance, and decoy systems have been 

 greatly emphasized by the advent of high-speed, nuclear-powered, sub- 

 marines and surface ships. Also, the increased emphasis in ocean- 

 ography and deep-water search activities indicates a greater use of cable- 

 towed devices. A more exact knowledge of the configuration and forces 

 produced by most of these systems will be required since they must be 

 accurately located relative to the towing platform for detection, tracking, 

 and fire control purposes. Furthermore, housing and power restrictions 

 of many towed systems preclude the installation of instrumentation to 

 monitor the towing configuration and forces during operation. 



To carry out the objectives of the subject program, the Model Basin 

 equipped an existing body with special purpose instrumentation and towed 

 it at sea by bare cable to obtain steady- state configuration data. The 

 experimental data were then compared with corresponding values obtained 

 by means of each of the two prediction methods. Based on these comparisons, 

 a set of "loading functions" was selected that should result in reasonably 

 accurate predictions of steady-state configurations and tensions for body- 

 dominated towed systems. 



This report describes the towed system, associated equipment, and 

 the experimental program used to provide the fundamental data for the 

 investigation; discusses the computer program used for the analysis; 



