The present study examines the possibility of completing gappy flow fields with the method of gappy proper orthogonal decomposition (GPOD). The procedure is performed on a numerically simulated cavity flow. The DNS data is artificially made incomplete by randomly omitting localized data. Two levels of gappiness are examined to evaluate the GPOD procedure. The results indicate that the relative error between the GPOD estimation and the real field directly depends on the level of gappiness. As the gappiness increases, the prediction accuracy decreases. It is shown that the relative error does not monotonically decrease because of inherent noise in higher-level modes of energy. The optimal count of modes in GPOD procedure is obtained and discussed. The contribution of GPOD procedure on spatial experimental data is also addressed. Manuscript profile

Lid-driven cavity flow is characterized by large-scale energetic eddies which are potential for energy harvesting purposes. The present article deals with numerical study of vortex-induced autorotation of an elliptic blade hinged at the center of a lid-driven cavity.Immersed boundary method is utilized to solve the governing equations for this moving boundary problem. Four different blade dimensions are considered at a fairly high-Reynolds number to evaluate the impact of various vortex types and flow unsteadiness on the blade dynamics. Small-amplitude fluttering, clockwise autorotation and counter-clockwise autorotation are three dominant modes observed at various configurations and different temporal stages. The average-length blade is equally characterized by vortices at both directions, and consequently experiences a fluttering mode. In contrast, short (long) bladeis mainly affected by one dominant vortex type, leading to steady autorotation in counter-clockwise (clockwise) direction. At stable autorotation of blade in both directions, regular cyclic temporal oscillations are observed in the rotational speed, which are due to cyclic evolution of the near-blade vortices and their alternating moment applied to the blade. Manuscript profile