Oscillating flow about circular cylinders at low Keulegan-Carpenter numbers.

摘要

The in-line force and the resulting drag and inertiacoefficients for smooth and rough circular cylindersimmersed in a sinusoidally oscillating flow at low Keulegan-Carpenter numbers (K) have been determined experimentallyand compared with those obtained theoretically by Stokes andWang. In addition, flow visualization experiments werecarried out with oscillating cylinders in a water table andthe stability of the flow was investigated. The resultshave shown that for very low values of K, the flow about thecylinder is laminar, attached, and stable and the dragcoefficient is nearly identical to that predicted theoretically. At a critical K, the flow becomes unstable toTaylor-Gortler vortices and the drag coefficient jumps to ahigher value. Subsequently, the flow separates, becomesturbulent and results in a minimum drag coefficient. Thesubsequent increases in drag are attributed to vortexshedding. The inertia coefficient agrees with that obtainedtheoretically in the range where the flow in laminar.