Abstract
The present study proposes a new method to visualize the characteristics of periodically oscillating two-dimensional flow around a wing section by evaluating the local time delay using correlation analysis of the pressure gradient along the surface. The local time delay for a pair of arbitrary two points on the surface is visualized on the two-dimensional map (the correlation map) with both the horizontal and vertical axes describing the coordinate along the surface. To demonstrate the validity and the usefulness of the present method, the time-series data of the unsteady flow field are obtained from the numerical simulation around a NACA0012 wing section at Reynolds number 104. The correlation map clearly divides the flow field near the body into the region with almost stable flow, that with small amplitude velocity fluctuation and that with significantly oscillating flow. The advection velocity of the vortices shedded from the separation bubble is successfully estimated from the pattern of the correlation map. Furthermore, the spatial and temporal resolution necessary for the present method is determined. Consequently, the present method is useful for extraction of the characteristics of the periodically oscillating flow around a body, when the time-series data of the surface pressure distribution are available.
