Swirling streamline-curvature law of the wall from a novel perturbation analysis

ri new law of the wad for swirling axial boundary layers is derived analyti cally, which accounts for local streamline curvature effects. Compared to p revious derivations, the new law covers a wider range of streamline curvatu re, y(+), and the axial-to-swirl sheer stress ratio. Incorporation of the l ocal streamline curvature physics gave greatly increased mathematical diffi culty. The difficulty was handled by developing a novel perturbation soluti on approach, which is thoroughly presented. This new solution approach allo ws a closed-form analytical solution to many similar nonlinear problems whi ch heretofore required numerical techniques. To demonstrate the worst-case scenario for swirl prediction (computational fluid dynamics, CFD) improvement, the new law of the wad was implemented in the standard k-epsilon model as a wall function. The new law gives CFD sol utions in closer agreement with measurements than does the classical log la w.