The Influence of Yaw Angle Upon the Vortex Wakes of Stationary and Vibrating Cylinders.
Abstract
This report investigates the influences of yaw angle and end condition upon the vortex wakes of finite-length, yawed circular cylinders. The standard for comparison is the Independence Principle which produces the so-called Cosine Laws for yawed body flows. These expressions have found widespread use even though their validity cannot be proved theoretically for separated, unsteady or turbulent flows. Many previous empirical checks of the Principle under these conditions have produced conflicting reports. Measurements of the vortex shedding frequency, the shedding angle, the base pressure, the vortex formation length and the wake width were obtained for both stationary and vibrating yawed cylinders in the range of Reynolds numbers Re = 160 to 1100. The influence of end conditions was assessed for free-ended cylinders of varying end geometries and for cylinders fitted with adjustable endplates. The cylinder lengths varied from about 20 to nearly 100 diameters. Based upon the experimental results and upon some fundamental considerations of the vorticity discharged at separation it is concluded that the use of the Independence Principle is not valid for separated, yawed cylinder flows except in two special cases. For the first time the 'universal' Strouhal number concept for scaling the vortex wakes of bluff bodies at normal incidence is found to be valid for inclined cylinders.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1978
- Accession Number
- ADA062417
Entities
People
- Steven E. Ramberg
Organizations
- United States Naval Research Laboratory