The wall signature of hairpin packets in turbulent boundary layers

We use a direct numerical simulation database (Martin, 2006;\footnote{Martin, M.P., J. Fluid Mech., Vol. 570, pp. 347-364, 2006.} Martin, 2004\footnote{Martin, M.P., AIAA Paper 2004-2337}) of turbulent boundary layers, statistical tools (Brown \& Thomas, 1977\footnote{Brown, G.L. \& Thomas, A. S. W., Phys. Fluids, Vol. 20, No. 10, Pt. II, pp. 243-251, 1977}) and pattern recognition and tracking algorithms (Wang \& Silver, 1997\footnote{Wang, X. \& Silver, D., IEEE Transactions on Visualization and Computer Graphics, Vol. 3, No. 2, pp. 129-141, 1997}; Richdale, 2007\footnote{Richdale, G.C., Senior Thesis, Princeton University, 2007}) to identify hairpin packets and their wall signature. The visualization algorithms are validated against the statistical analyses. We investigate the variation of time scales and length scales associated with coherent structures and the role of hairpin packets on the generation of skin friction, wall-pressure loading and heat transfer.