Radiation from large-scale structures within a turbulent shear layer

Large-scale finite-wavelength modulation within turbulent shear flows.

We show that turbulent "spirals" and "spots" observed in Taylor-Couette and plane Couette flow correspond to a turbulence-intensity modulated finite-wavelength pattern which in every respect fits the phenomenology of coupled noisy Ginzburg-Landau (amplitude) equations with noise. This suggests the existence of a long-wavelength instability of the homogeneous turbulence regime.

Forced Turbulent Shear Layer

Bubble breakup in a turbulent shear layer

The breakup of a millimetre size buoyantly rising bubble encountering a horizontal plane turbulent jet is experimentally investigated using high-speed shadowgraphy and acoustic techniques. The bubble diameter to jet height ratio is 0.75 and the jet height based Reynolds number is 4000. The high-speed imaging was recorded at 7 kHz simultaneous with hydrophone output at 100 kHz. Bubble breakup ev...

Shear-current effect in a turbulent convection with a large-scale shear.

The shear-current effect in a nonrotating homogeneous turbulent convection with a large-scale constant shear is studied. The large-scale velocity shear causes anisotropy of turbulent convection, which produces the mean electromotive force epsilon (W) proportional to W x J and the mean electric current along the original mean magnetic field, where W is the background mean vorticity due to the sh...

Influences of Large-scale Structures on Skin Friction in an Adverse Pressure Gradient Turbulent Boundary Layer

Direct numerical simulation (DNS) of a turbulent boundary layer (TBL) subjected to adverse pressure gradient (APG) at Reτ = 834 is performed to investigate large-scale influences on vortical motions. For comparison, DNS data of a zero pressure gradient (ZPG) TBL at Reτ = 837 is analyzed. The spanwise energy spectra of the streamwise velocity fluctuations show that the large-scale energy above 4...