Transition along a finite-length cylinder in the presence of a thin boundary layer

Abstract

This work aims to investigate experimentally the transition of the aerodynamic forces on a cantilevered circular cylinder immersed in a thin boundary layer whose thickness is comparable to the cylinder diameter d. The aspect ratio H/d of the cylinder is 5, where H is the cylinder height. The Reynolds number Re, based on the freestream velocity (U ∞ ) and d, is varied from 0.68 × 105 to 6.12 × 105, covering the subcritical, critical and supercritical regimes. It has been found that the flow transition is non-uniform along the cylinder span, taking place at a smaller Re near the cylinder free end than near the base. Furthermore, the sectional drag coefficient of the cantilevered cylinder is smaller relative to that of a two-dimensional cylinder in the subcritical regime, but larger than the later in the supercritical regime. The sectional lift coefficient is not zero in the critical regime, with its maximum near the free end reaching almost four times of that near the base.