CONCEPTUAL OVERVIEW OF LAMINAR AND TURBULENT FLOWS PAST SMOOTH AND ROUGH CIRCULAR-CYLINDERS

Flow around a circular cylinder is governed by three transitions: in-the-near-wake, along the free shear layers and along the boundary layers. Each transition is characterized by several flow regimes which are sensitive to disturbances. The variation of mean and fluctuating lift and drag coefficients, friction and pressure coefficients are compiled in the range 100<Re<108 for the disturbance-free flow. The concept of possible inversion of influencing to governing parameters and vice versa is applied to rough cylinders and turbulent flow. The free stream turbulence and surface roughness affect differently the three transitions and may cause an obliteration of some flow regimes in addition to moving the transition state as a whole to lower Reynolds number. © 1990.