A vorticity stretching diagnostic for turbulent flows

QC 20181026
Vorticity stretching in wall-bounded turbulent and transitional flows has been investigated by means of a new diagnostic, designed to pick up regions with large amounts of vorticity stretching. It was found that the largest occurrence of vorticity stretching in fully turbulent channel flows is present at a wall-normal distance of y+ = 6.5, i.e. in the transition between the viscous sublayer and the buffer region. Instantaneous data showed that the coherent structures associated with these stretching events have the shape of flat ‘pancake structures’ in the vicinity of high-speed streaks, here denoted ‘h-type’ events. The other event found, also studied in an asymptotic suction boundary layer, is the ‘l-type’ event present on top of an unstable low-speed streak. These events are further thought to be associated with the exponential growth of streamwise vorticity in the turbulent near-wall cycle.

TEKNIK OCH TEKNOLOGIER Maskinteknik Strömningsmekanik och akustik hsv//swe
ENGINEERING AND TECHNOLOGY Mechanical Engineering Fluid Mechanics and Acoustics hsv//eng
Atmospheric thermodynamics
Boundary layers
Channel flow
Turbulence
Vorticity
Buffer region
Coherent structure
Exponential growth
Normal distance
Pancake structure
Transitional flow
Turbulent channel flows
Viscous sublayer
Shear flow

Ingår i:7th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2011: International Symposium on Turbulence and Shear Flow Phenomena, TSFP

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