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The three-dimensional flow around a custom wing performing pitching oscillation is analyzed numerically using large-eddy simulation with the wall adapting local eddy-viscosity subgrid-scale model. The wake characteristics behind the pitching wing with three different aspect ratios, AR = 2 / 3 , 1 , 4 / 3 , is investigated in an upstream flow with Reynolds number, Re = 2640. The Q − function is employed to identify the swirling structures in the flow field, and four primary vortices, namely, primary leading edge vortex (PLEV), secondary leading edge vortex, wing tip vortices, and trailing edge vortex, are identified. The evolution of vortices over the wing surface is presented in detail, and the arrangement of vortex rings in the wake is compared for three different aspect ratios. The PLEV develops into an arch vortex using the self-induction phenomenon, and the interlinking between the subsequent vortex rings depends on the arch vortex leaving the trailing edge. The force coefficient computed over the wing shows a positive thrust for AR = 4 / 3. The mean velocity field contours indicate a spanwise loading on the wing, which is unaccountable in two-dimensional studies. The Reynolds stresses generated due to large-scale periodic velocity fluctuations in the wake are presented. The vorticity field in the midplane of the wing appears to be diffusive at higher aspect ratios. The comparison of vorticity from the three-dimensional and two-dimensional models suggests that a two-dimensional model will over predict the vorticity distribution and force coefficients in the wake. [ABSTRACT FROM AUTHOR]

Large eddy simulation (LES) with dynamic Smagorinsky model (DSM) has been implemented to elicit the turbulence characteristic of the flow inside a cubic lid-driven cavity at Reynolds number of 10000. The coherent organized structures tear, pair and disintegrate leading to the evolution of turbulence. They are reflected in the RMS (root mean square) plots of the turbulent fluctuations in different planes. The flow has a near zero helicity value; unlike the other two velocity component, the probability density function of span wise velocity component shows the flow symmetry on the both side of the mid plane in span wise direction; kurtosis being largely leptokurtic except near wall locations indicates their peakedness. The quadrant analysis shows presence of more coherent structures near the down stream wall and the joint probability distribution function shows that turbulence is anisotropic. Power spectra is observed to follow the − 5 ∕ 3 law. Both Taylor microscale λ and Kolmogorov length scale η show greater near-wall dissipation • Large eddy simulation of cubic lid-driven cavity flow has been performed at Re =10000. • Q- criterion shows the coherent organized structures tear, pair and disintegrate leading to the evolution of turbulence. • The Fourier spectra of auto correlation shows a slope of − 5 ∕ 3 in the sub inertial range. • The probability density function of span wise velocity component on the symmetrical mid plane shows the flow maintains symmetry even at high Reynolds number and has very low skewness value. Kurtosis is mostly leptokurti except near wall location. • Joint probability density function shows the turbulent fluctuations distribution is anisotropic. [ABSTRACT FROM AUTHOR]