Gust Response of Free-Falling Permeable Plates

This paper investigates the effect of discrete transverse gusts on the flight dynamics and descent velocity of two-dimensional free-falling permeable plates. Two-way coupled fluid-structure interaction simulations are carried out using an overset meshing strategy for a range of Galilei number (Ga) from 10 and 50, and of the nondimensional mass (m) from 0.5 to 2, and a fixed Darcy number (Da) of $10^{-4}$. The present results show that the plate falls steadily in quiescent flow at the lowest Ga and m values; whereas, fluttering and tumbling are observed for increased Ga and /or m. Transverse (horizontal) gusts temporarily decrease the terminal velocity of the plate in the transient regime. Consequently, a plate experiencing a transverse gust travels less vertical distance than a plate falling in quiescent flow over the same period of time. The gust effect increases with the gust acceleration, Ga and m. The underlying uplifting mechanism is not directly related to the permeability, and it is thus likely to occur also for impermeable bodies. The present findings might provide insights to interpret the effect of turbulence on the terminal velocity of free-falling bodies and inform the design of insect-scale flyers passively transported by the wind

Identifying ‘authorized users’, identifying kin: negotiating relational worlds through Geographical Indications registration

The Geographical Indications of India Act requires a detailed description of ‘authorized users’ and ‘producers’ without concern for how these ‘producers’/ ‘authorized users’ are identified and what are the outcomes of such identification. Artisans identified as producers of GI registered ‘Cheriyal Painting’ of Telangana primarily belong to one genetically related family. Apart from members of the Danalakota household, GI also enumerates families of apprentices as ‘producers’. This article will highlight two things. First, it will demonstrate the way in which identification of ‘producers’/ ‘authorized users’ replicates not only the relational worlds within which producers exist but also the ‘obligations and moral imperatives’ embedded within those relations. Second, identifying oneself as a ‘producer’/ ‘authorized user’ requires distinguishing and individualizing one’s relatedness with the Danalakota family; promises of welfare by the state then become accessible only by becoming kin and distinguishing oneself as kin

A two-coil mutual inductance technique to study matching effect in disordered NbN thin films

Although matching effects in superconducting anti-dot arrays have been studied extensively through magneto-resistance oscillations, these investigations have been restricted to a very narrow temperature window close to the superconducting transition. Here we report a "two coil" mutual inductance technique, which allows the study of this phenomenon deep in the superconducting state, through a direct measurement of the magnetic field variation of the shielding response. We demonstrate how this technique can be used to resolve outstanding issues on the origin of matching effects in superconducting thin films with periodic array of holes grown on anodized alumina membranes

Meet on digital humanities at IIT-Hyderabad

The Liberal Arts department and Sahapedia organised a two-day interdisciplinary conference to discuss challenges in Digital Humanities in relation to Arts, Knowledge, and Critique in the Digital Age in India

Transition boundaries and an order-to-chaos map for the flow field past a flapping foil

peer reviewedThe present study focuses on identifying dynamical transition boundaries and presents an order-to-chaos map for the unsteady flow field of a flapping foil in the low Reynolds number regime. The effect of an extensive parametric space, covering a large number of kinematic conditions, has been investigated. It is shown that the conventional non-dimensional parameters cannot effectively capture the changes in the flow field due to the variations in the relevant kinematic parameters and are unable to demarcate the dynamical transition boundaries. Two new non-dimensional measures - maximum effective angle of attack and a leading-edge amplitude-based Strouhal number - are proposed here, which can capture the physical effect of the parametric variations on the wake dynamics. The study proposes generalised transition boundaries and an order-to-chaos map through a transitional regime in terms of these two newly proposed parameters. Published data from the existing literature have also been tested to verify the proposed transition model. It is seen that despite the wide variety of the parametric combinations, the dynamical states from both the new and the published data corroborate well the proposed boundaries, giving credibility to the order-to-chaos map

Origin of Matching Effect in Anti-dot Array of Superconducting NbN Thin Films

We investigate the origin of matching effect observed in disordered superconducting NbN thin films with periodic array of holes. In addition to the periodic variation in the electrical resistance just above the superconducting transition temperature, Tc0, we find pronounced periodic variations with magnetic field in all dynamical quantities which can be influenced by flux-line motion under an external drive such as the magnetic shielding response and the critical current which survive in some samples down to temperatures as low as 0.09Tc0. In contrast, the superconducting energy gap, D which is a true thermodynamic quantity does not show any periodic variation with magnetic fields for the same films. Our results show that commensurate pinning of the flux line lattice driven by vortex-vortex interaction is the dominant mechanism for the observed matching effects in these superconducting anti-dot films rather than Little-Parks like quantum interference effect.Comment: 18 pages, 6 figure

Controlling the chaotic wake of a flapping foil by tuning its chordwise flexibility

Effects of chord-wise flexibility as an instrument to control chaotic transitions in the wake of a flexible flapping foil have been studied here using an immersed boundary method-based in-house fluid-structure-interaction solver. The ability of the flapping foil at an optimum level of flexibility to inhibit chaotic transition, otherwise encountered in a similar but rigid configuration, has been highlighted. The rigid foil manifests chaotic transition through a quasi-periodic-intermittency route at high dynamic plunge velocities; whereas, increasing the level of flexibility gradually regularises the aperiodic behaviour through a variety of interesting wake patterns. If flexibility is increased beyond an optimum level, aperiodicity sets in again and robust chaos is restored at very high flexibility levels. The mechanisms of triggering the order-to-chaos transition are different between the rigid and the high flexibility cases. Along the route to order and back to chaos, the flexible foil exhibits different flow-field behaviours, including far-wake switching, primary \& secondary vortex streets, bifurcated wakes and interactive vortices between the bifurcated wakes. The underlying interaction mechanisms of the flow-field vortices responsible for the associated dynamical signatures of the wake have been closely tracked. This study further examines the optimum propulsive performance range of the flexible flapper and investigates its connection with the periodicity/regularity of the system