Numerical investigation of turbulent drag reduction by streamwise–spanwise discontinuous microgrooves in natural gas pipelines

During high-pressure natural gas transportation, significant frictional losses arise due to turbulence-induced wall shear. Conventional bionic microgroove surfaces can suppress near-wall vortical structures and thus reduce drag to some extent; however, their effective drag-reduction range is limited, and they tend to deteriorate or even reverse to drag enhancement under high Reynolds number conditions. To address this limitation, a novel streamwise–spanwise two-dimensional discontinuous microgroove inspired by the tactile paving pattern (“blind path”) is proposed in this study. A 45° smooth transition angle is introduced in the groove design to mitigate local flow separation. Based on large eddy simulation combined with the wall-adapting local eddy-viscosity subgrid-scale model, the drag-reduction performance of the proposed two-dimensional discontinuous groove and the conventional alternating-width semicircular groove was comparatively evaluated over the Reynolds number range of Re = 1.30 × 105–6.54 × 105. The results indicate that the discontinuous groove achieves a maximum drag reduction of 18.08% at Re = 2.0 × 105, outperforming the traditional configuration and maintaining effectiveness across a broader Reynolds number range. Mechanistic analysis reveals that the proposed groove effectively suppresses the formation of quasi-streamwise vortices in the near-wall region and displaces the high-disturbance zone away from the wall, thereby significantly reducing wall shear stress and velocity fluctuations.