TURBULENCE STRUCTURES OF WALL-BOUNDED SHEAR FLOWS FOUND USING DNS DATA

This work extends the study of the structure of wall-bounded flows usi ng the topological properties of eddying motions as developed by Chong et al. (1990), Soria et al. (1992, 1994), and as recently extended by Blackburn et al. (1996) and Chacin er al. (1996). In these works, reg ions of flow which are focal in nature are identified by being enclose d by an isosurface of a positive small value of the discriminant of th e velocity gradient tenser. These regions resemble the attached vortex loops suggested first by Theodorsen (1955). Such loops are incorporat ed in the attached-eddy model versions of Perry & Chong (1982), Ferry et al. (1986), and Ferry & Marusic (1995), which are extensions of a m odel first formulated by Townsend (1976). The direct numerical simulat ion (DNS) data of wall-bounded flows studied here are from the zero-pr essure-gradient flow of Spalart (1988) and the boundary layer with sep aration and reattachment of Na & Moin (1996). The flow structures are examined from the viewpoint of the attached eddy hypothesis.