EFFECTS OF CONVEX TRANSVERSE CURVATURE ON WALL-BOUNDED TURBULENCE .2.THE PRESSURE-FLUCTUATIONS

The effects of convex transverse curvature on the wall pressure fluctu ations were studied through direct numerical simulations. The flow reg ime of interest is characterized by large ratio of the shear-layer thi ckness to the radius of curvature (gamma = delta/a) and by small a+, t he radius of curvature in wall units. Two direct numerical simulations of a model problem approximating axial flow boundary layers on long c ylinders were performed for gamma = 5 (a+ almost-equal-to 43) and gamm a = 11 (a+ almost-equal-to 21). The space-time characteristics of the wall pressure fluctuations of the plane channel flow simulation of Kim , Moin & Moser (1987), which were studied by Choi & Moin (1990) are us ed to assess the effects of curvature. As the curvature increases the root-mean-square (r.m.s.) pressure fluctuations decrease and the ratio of the streamwise to spanwise lengthscales of the wall pressure fluct uations increases. Fractional contributions from various layers in the flow to the wall r.m.s. pressure fluctuations are marginally affected by the curvature. Curvature-dependent timescales and lengthscales are identified that collapse the high-frequency range of the wall pressur e temporal spectra and the high wave-number range of the wall pressure streamwise spectra of flows with different curvatures. Taylor's hypot hesis holds for the wall pressure fluctuations with a lower convection velocity than in the planar case.