DNS of Turbulent Boundary Layers Subjected to Adverse Pressure Gradients

Abstract

Direct Numerical Simulations (DNS) of spatially-developing turbulent boundary layers with prescribed moderate and strong adverse pressure (APG) gradients are performed. A method for prescribing realistic turbulent velocity inflow boundary conditions is employed based on the on the dynamic multi-scale approach proposed by [1] [2]; and, it is an extension of the rescaling-recycling method by [6]. Comparison with data from more costly DNS ([7][5]) yields accurate results. In addition, the dynamic multi-scale approach does not require lengthy computational domains as in [7] and [5]. Furthermore, it is shown that in APG flows the presence of a second outer peak in \(u{^{\prime +}_{rms}}\) is more pronounce than in ZPG flows. Additionally, the plateau between the inner and outer peaks suggests the presence of an overlap (i.e., meso-layer) in the mean velocity profile, as discussed in GC-97 [3]. Moreover, these outer peaks are also observed in the production of turbulence even at low Reynolds numbers. Finally, the mean velocity profiles in wall-units show that the wake region is magnified as the APG strengths increases. This suggests that the large scales in the outer flow dominate most of the boundary layer.