Underlay mechanism in lift-drag phase diagrams for shear flow over cylinder

The characteristics of a uniform-shear flow over a circular cylinder are in- vestigated numerically by using the alternative-direction implicit （ADI） algorithm and a fast Fourier transform （FFT） one in the exponential-polar coordinates for Re = 150 and 0 ≤ K ≤ 0.46. The diagram of lift-drag phase, implying the detail information about the fluctuations of drag and lift as well as the flow patterns in the wake and fluctuating pres- sure on the cylinder surface, is used to describe the effects of the shear rate on the flow. Results show that the upper （or lower） closed curve of a phase diagram corresponds to the first （or second） half shedding cycle. The lift-drag phase diagram will move down-left with the increase of shear rate K such that the lift is exerted from the upper side to the lower side, and the drag on the first half shedding cycle is smaller than that on the second half.