Numerical study on the turbulent characteristics in parallel planes with wall blowing and suction

A spatiotemporal periodic blow–suction perturbation with instantaneous zero-net-mass-flux (ZNMF) constraint is proposed in this work and applied to drag reduction in turbulent boundary layer. A direct numerical simulation solver was used to analyze the influence of ZNMF perturbation in the turbulent boundary layer. In the present work, the bulk Reynolds number (Reb) was fixed to 2800. The characteristics of mean velocity profile, root mean square, Reynolds stress, and coherent structures are further analyzed. The results show that the wall periodic blowing/suction can obviously reduce the skin friction in streamwise direction, and the drag-reduction phenomenon can be sustained for a certain distance when it stops. An appropriate blowing/suction amplitude Abs = 0.0025 can reduce the mean velocity gradient in the viscous sub-layer while increasing that in the transition layer. With then increasing of perturbation amplitude, the streamwise and wall-normal fluctuation velocities increase first and then decreases. The case with an amplitude of Abs = 0.0025 can also reduce the spanwise velocity fluctuations, exhibiting a reduction of 1.068% near the wall. Observation of the flow coherent structures also reveals that an appropriate amplitude can ameliorate flow irregularity and clustering phenomena.