A visual assessment of hairpin packet structures in a DNS of a turbulent boundary layer

作者：Rahgozar S; Maciel Y^*

来源：European Journal of Mechanics - B: Fluids , 2016, 56: 161-171.

DOI：10.1016/j.euromechflu.2015.12.002

• Turbulent boundary layer
• Coherent structures
• Hairpin packet
• Direct numerical simulation
• Particle image velocimetry

A well-resolved DNS of a zero-pressure-gradient turbulent boundary layer at moderately high Reynolds number is analyzed in order to visually assess, in three dimensions, the existence of instantaneous realizations of outer region hairpins and hairpin packets. For this purpose, fifty independent 2D streamwise-wall-normal slices of DNS data at R-e theta = 4300 are employed to mimic lower-resolution PIV velocity fields using the mimicking procedure of Rahgozar et al. (2013). The two-dimensional structure identification scheme of Adrian et al. (2000) is then applied on this resolution-degraded DNS data in order to discover the signatures of hairpins and hairpin packets. Subsequently, the 2D motions that are identified as signatures of hairpins and hairpin packets are isolated and visualized in three dimensions using the fully resolved DNS data. In agreement with Adrian et al. (2000), the hairpin and hairpin packet signatures are frequently observed in the mimicked planes. However, the 3D character of the 2D signatures is found to be significantly different from the inferred hairpins and hairpin packets. The 2D packet signatures, when viewed in 3D, generally correspond to a series of irregular and complex vortex tubes which are not necessarily different from other nearby vortex tubes in terms of their shape, size and intensity.

• 出版日期2016-4