Several conclusions were drawn from these investigations. Among the most important of King's 

 findings was that yawing the structure provides no protection against vortex-excited oscillations, and sus- 

 tained oscillations both in line and cross flow were recorded for yaw angles up to = 45° both into and 

 away from the incident flow. The cylinder response was virtually the same whether the cylinder was 

 inclined into or away from the flow, and a typical example (for inclination into the flow) is given in Fig. 

 2.18. There the reduced velocity K, is based upon the normal component of the incident flow, Kcos /3, 

 where /3 is the angle between V and a plane that is normal to the axis of the structuret. The lower 

 peak displacement amplitudes again correspond to larger values of the reduced damping k^. The yawed 

 flexible cylinder results are plotted in Fig. 2.2 and are indistinguishable from the displacement ampli- 

 tudes measured at normal incidence. The critical reduced velocities for the onset of in line and cross 

 flow oscillations were once again found to be V, = 1.2 and V, = 3.5 to 5, with the appropriate velocity 

 term being V cos j8 . Similar results were obtained during the DTNSRDC towing channel experiments 

 discussed in Section 3.2. A marine cable that was inclined at an angle /8 = 30° underwent large cross 

 flow strumming displacement amplitudes (29), and the shedding was completely locked on to the 

 resonant vibrations. 



King also made a detailed study of yaw angle eff"ects on the drag coefficient of a stationary 

 cylinder. This aspect of the investigation demonstrated that if the normal component of velocity, Kcos 

 j8, were employed as the velocity scale, then a consistent value of drag coefficient C^ was obtained, and 

 that the value of C^ so obtained was equal to the equivalent value for a cylmder at normal incidence. 

 Ramberg's findings suggest that the drag estimated in this way may be low and somewhat dependent on 

 the experimental arrangement (28). 



Ramberg undertook a detailed investigation of the flow around yawed cylinders; the primary 

 objective was an examination of the Independence Principlet and how it can be used correctly. This 

 principle, as noted above, states that the proper velocity scale for characterizing the flow about and 

 forces on bluff" bodies is the component of the incident flow normal to the body. One conclusion of 



tThe use of normal component of velocity is called the "Independence Principle;" this is discussed in further detail later in this 

 section. 



20 



