Hairpin vortices in turbulent channel flow

The phenomenon of birth and development of hairpin vortices in the wall region of turbulent channel flow is investigated numerically. The system of the Navier-Stokes equations is integrated by using a mixed spectral-finite difference numerical technique following the procedure of the Direct Numerical Simulation of turbulence (DNS), with accuracy requirements such that all the essential turbulent scales are resolved. The value of the Reynolds number based on wall-shear velocity and channel half height is 200 = Reτ. A specially-assembled computing machine is used for the calculations, that includes one Intel® i7 Core™ quad-core processor, and two Nvidia® C-1060 Tesla™ devices. The swirling-strength criterion for vortex eduction is applied to the fluctuating portion of the computed velocity-field numerical database, and the resulting hairpin vortical structures are visualized as they evolve with time in the computing domain.